OUR NATIVE TREES

The Native Trees & Shrubs of the Arboretum

Like people, trees come in a remarkably diverse range of sizes and shapes and with a suite of characteristic features. But despite this diversity, trees and people are united by basic needs. Both trees and people need food, water, shelter, and companionship. Companionship? A growing body of research is shedding light on how some trees – even different species of trees – can assist each other via underground fungal mycorrhizal connections.

Like people, different species of trees offer a mix of qualities that help us decide whether to make them our companions. Again, like people, no one species of tree is perfect, but among the trees in the arboretum are at least some that would be excellent arboreal companions in your yard.

In the following notes for the tree species in the arboretum you’ll find statistics referencing the number of caterpillars that feed on the foliage. You may well ask why you’d want caterpillars feeding on your tree. The answer has everything to do with the songbirds that eat those caterpillars and feed them to their young. Caterpillars are critically important to our songbird populations. Rest assured that the caterpillars we want are native species, not the invasive LDD caterpillars. Native species of caterpillars seldom injure thriving trees.

Regardless of the species of tree you choose to plant, note that all of them during their first year after planting, require lots of water. In years two and three a drink in especially dry periods is recommended.

Here are some notes to help you get to know the trees of the arboretum better.

Native Trees

American Elm

Ulmus Americana

You’d be forgiven for wondering why we’ve included this species in the arboretum planting. After all, this species has been decimated by Dutch elm disease. Beautiful trees, but why plant them only to watch them succumb to a virulent pathogen? The answer is replete with hope. For decades research programs in the United States and here in Canada at Guelph University have been seeking disease resistant strains. That research is starting to pay off with several Dutch elm disease resistant white elm selections now identified. So with an cautious optimism, arborists and urban parks’ departments are planting elm again. If these new selections do indeed remain healthy despite being exposed to Dutch elm disease, an enormous coup for the environment will have been achieved. And all who value diversity and the aesthetic magnificence of a mature elm tree will be able to rejoice.

Virtues: Fast growing, extremely cold tolerant, adapts to dry or wet soils. Mature specimens are unlike any other native tree with a wonderful umbrella form. A superb shade tree with the lower branches elevated high above the ground.

Wildlife Value: When elms were common they were the favourite nesting trees of the glorious Baltimore orioles. The orioles would dangle their distinctive pendulous nests from the ends of elm branches. Elm foliage supports over 200 species of caterpillars. The seeds are consumed by many birds and small mammals.

Needs: Requires a fair amount of space. Planting one could be perceived as an act of faith, as a roll of the dice. But consider that any successful planting will contribute to the renaissance of this wonderful species.

Local Examples: Isolated mature elms can still be found throughout Halton Region and throughout Ontario. One beautiful specimen that has yet to attain its full stature, has grown alongside Guelph Street in Georgetown for decades in front of the former Cooper Standard building.

These trees should be planted where they have lots of room to grow into a broad vase shape. Massive trunks and large limbs support dark green foliage which turns yellow in the fall. When planting, choose a cultivar that is resistant to the devastating Dutch elm disease.

American Sycamore

Platanus Occidentalis

Sycamores have distinctive (and lovely!) mottled bark that sets them apart from all other native trees. Similar though is the London plane tree, a hybrid between our sycamore and an Asiatic species. London plane trees are frequently offered in nurseries so if you want a purebred sycamore ask for it by its scientific name. Sycamores are generally floodplain trees in southern Ontario, and though they don’t reach Halton Hills in the wild, they can be found just to the south along Bronte and Oakville Creeks. In those settings, in Burlington and Oakville respectively, they stand out as perhaps the most impressive trees among their companions. This is especially true in winter, when the white-brown mottled bark fairly glows in the sun.

Virtues: The bark, mentioned above, is a big part of the appeal of sycamores. They are fast growing and though they are found along streams in the wild, they are adaptable to urban conditions.

Wildlife value: Before they were cut in the almost total deforestation of our landscape as European settlement progressed, we had some giant sycamores. Some were hollow, attracting roosting and nesting chimney swifts. Sycamores produce ping-pong sized seed balls that hang on the trees in the winter, feeding some of our songbirds.  

Needs: Lots of water until well established. Will tolerate part shade, but best in sun.

Local Examples: Greenwood Cemetery in Georgetown has a fine old sycamore. The Royal Botanical Arboretum on Old Guelph Road in Hamilton has several gorgeous mature specimens.

Basswood

Tilia americana

Basswood is another common component of Halton’s deciduous forests, growing alongside maples, ashes and black cherries. It grows tall in these forest situations but where it gets more sun, in hedgerows for example it is shorter but attains a greater spread. Basswood sports large heart-shaped leaves. Its distinctive red buds allow it to be easily identified in winter.

Virtues: Quick growing and adaptable to shade or sun and various soil types. The soft wood is sought after by wood carvers.

Wildlife Value: One of the few trees in the forest that depends on pollinators to set seed. (Most other woodland trees are wind pollinated.) Bees love basswood blossoms and the honey they make from basswood nectar is highly prized. Old basswood trees are often hollow, offering vital accommodation to all manner of birds and mammals.

Needs: There are no significant concerns when basswood is young, but heavier limbs may break when it gets older.  Because of this, situate basswood away from houses and other structures to be on the safe side.

Local examples: Seek basswood along the Bruce Trail or the Hungry Hollow Trail in Georgetown. Look for its distinctive leaves, or in the winter, its red buds.

Black Cherry

Prunus serotina

Black Cherry is a common large tree in area woodlands, associating with sugar maple, basswood and white ash. It is readily identified when mature by dark, flaky bark. Straight, forest-grown specimens are valuable trees. Black cherry is highly sought after for furniture, cabinetry and other uses.

Virtues: Quick growing, long-lived and adaptable to various soil types. Can grow quite well in shade.

Wildlife Value: Bees are drawn to the pendant white flowers of this tree and birds relish the profuse small black fruit that follows. Black cherry is one of our best caterpillar trees and hence one of the best songbird supporters we have.

Needs: The vast majority of those caterpillars don’t harm the trees, but you will likely need to control the invasive LDD caterpillars and the native tent caterpillars when the trees are young. Black cherry is best planted away from sidewalks and driveways because of its fruit production. It is comfortable growing close to other tree species, as it does in the wild.  

Local examples: After familiarizing yourself with its distinctive bark, a walk along the Bruce Trail in Halton Hills will yield examples of black cherry.

Bur Oak

Quercus macrocarpa

This is one tough tree. Burr oak ranges further north than any other oak in North America, extending well into the Interlake Region of Manitoba. Many of the stand-alone trees in farm fields in Halton are this species, exposed to heat, drought and howling winter winds.  Burr oaks also grow on floodplains and there, in deep moist soils, can become giants, with diameters approaching two metres. Planting an oak is an investment in the future, for they have life spans of 300 years or more.

Virtues: Once established needs no care. Grows in a range of soils including the clay of Halton Hill’s suburbia. Rock hardy. Statuesque, as many oaks are, in maturity.

Wildlife Value: Oaks are recognized by Professor Douglas Tallamy the author of Bringing Nature Home, as the premier wildlife trees. They feed more caterpillar species (500+) than any other tree and those caterpillars, in turn, feed our birds. Blue jays, woodpeckers and squirrels value the acorns of burr oak over our other native oak species.

Needs: All oaks are sun lovers and burr oak is no exception. Due to its ultimate size, it should be given plenty of space.

Local Examples: A large burr oak has dominated the skyline of McIntyre Crescent in Georgetown for many decades. In Meadowvale Conservation Area near the Credit Valley Conservation headquarters a few impressively large burr oaks can be found.

Callery Pear

Pyrus calleryana

Choosing a tree for the residential or commercial landscape was formerly driven almost solely by aesthetics – the perceived beauty of the tree. Considerations to guide selection included the tree’s ultimate shape, its flowers and its foliage colour in autumn. Callery pear rates highly on all these metrics. It has a pleasing conical or rounded crown, abundant white blossoms in spring and lustrous red fall colour.

So callery pear would seem a tree worthy of purchase, right? Well, not if you value trees for more than their appearance. If you also value them for their wildlife value and their contribution to your local ecology, callery pear should not be your choice. In “Bringing Nature Home, How Native Plants Sustain Wildlife in Our Gardens”, author Douglas Tallamy gives callery pear a big thumbs down. He calls this ornamental tree “biological pollution”. In the northeastern United States it has become a major invasive threat, along with Norway maple. It could become a major issue with us in the years ahead.

Why does this matter? Callery pear is still a tree after all, and in spring and autumn it’s lovely. It’s a problem because, as a non-native, it is almost totally ignored by insects. Tallamy has found only one species of caterpillar eating its leaves for example. Why is that a problem? Because insects feed our songbirds (and a host of other creatures!) Without insects we will have fewer chickadees and bluebirds and warblers.

So please, when you decide to buy a tree, consider not only its beauty, but importantly, its potential contribution to birds and the local ecology.

Cucumber Magnolia

Magnolia acuminata

Cucumber magnolia is a very rare tree in Ontario, confined to a few small patches in Niagara Region and Norfolk County. As magnolias go, it is ultimately a large tree. Cucumber magnolia doesn’t produce the opulent colourful blossoms of the horticultural magnolias that make such bold statements on urban landscapes in the spring. Cucumber magnolia still has great aesthetic charm however, just more subdued. Its leaves are large and glossy – almost tropical in appearance. Open grown trees assume an appealing pyramidal shape. The red fruit pods in the fall are notable, producing an abundance of seeds covered by pink-orange flesh.

Virtues: Its rarity is a virtue. We should give this fascinating native tree more places to grow. As mentioned above the foliage and form of this tree and its unusual fruit are selling points.

Wildlife Value: The seeds are consumed by a variety of birds and mammals.

Needs: Cucumber magnolias grow in moist loams in the wild, conditions that can be in short supply in suburbia. Our arboretum magnolia will serve as a test of their suitability for planting in Halton Hills. However, we are guardedly optimistic that this unique tree will grow well in this area. There are hybrid magnolias with cucumber magnolia as one of their parents, already growing here. Moreover, cucumber magnolias at the University of Guelph arboretum are lovely and robustly healthy.

Local examples: As mentioned, the arboretum at the University of Guelph has several wonderful specimens of this rare native. They are perhaps thirty or forty years old, demonstrating long-term viability in our climate. The Royal Botanical Gardens arboretum in Hamilton also has large healthy cucumber magnolias.

Kentucky Coffee Tree

Gymnocladus dioicus

A species that pines for the mastodons and ground sloths of the Pleistocene. A theory suggests that these mega-beasts fed on the Kentucky Coffeetree seed pods and then dispersed the seeds in their droppings. With the extinction of wild elephants and sloths in North America, so the story goes, the Kentucky Coffeetree was left without its main benefactors. Regardless of whether this theory is correct, it does appear that Homo sapiens are now the main dispersal agents of this species. We’ve helped it to expand into towns and cities well removed from the few spots where it is native in southwestern Ontario.

Virtues: Though not native this far north, Kentucky Coffeetree is entirely hardy here. Presumably the mastodons didn’t wander through north Halton with Kentucky Coffeetree seeds in their guts. It offers lovely late emerging light green foliage. These trees are handsome throughout their long lives.

Wildlife Value: Alas, the mega-fauna that once fed on the fruit of this species are gone, but some smaller creatures will nibble on the sweet pods while ignoring the rock-hard seeds.

Needs: Needs full sun to thrive. Fast growing and drought tolerant. Increasingly recognized as a valuable street tree. One caution: if cut will likely sprout profusely from its base. May occasionally sucker anyway, necessitating some control.

Local Examples: Only recently has this species become common in urban landscaping but fine specimens can be found at the Guelph University arboretum.

Mulberry

Morus rubra

Red mulberry is an endangered species in Ontario. Only two hundred or so individual trees remain in scattered locations in the Carolinian Zone. Complicating matters is the fact that invasive white mulberries (Morus alba) are popular in the nursery trade and may deliver the coup de grace to our red mulberries through hybridization. Close to 100% of the mulberries that grow in our urban areas are the imported white mulberries. Though the fate of our native mulberry may already be sealed, for now at least, the best advice is to avoid planting white mulberry.

Virtues: All mulberries, native and introduced, produce delectable fruit, sought after by people and all manner of wildlife. Red mulberry is a fast-growing small tree adaptable to a variety of soil conditions.

Wildlife Value: Robins, waxwings, cardinals and many other species of birds love red mulberry fruit.

Needs: Red mulberry can tolerate a variety of soil types. It does appreciate some shade.

Local Examples: The University of Guelph Arboretum has a fine mature red mulberry.

Special Note: This species is very difficult to find in the nursery trade. The ones in the arboretum were purchased as small saplings from Grimo Nut Nursery in Niagara-on-the-Lake. Please don’t plant mulberry unless you can find a reputable nursery that can verify your purchase as pure red mulberry stock.

Norway Maple

Acer platanoides

Beware the imposter! Norway maple on the surface, looks like our beloved sugar maple – the quintessential Canadian tree. Sugar maple leaves symbolize our country, emblazoned on backpacks, hockey jerseys and, of course, our flag. Sweet sap pushing upwards through its xylem in spring is tapped to yield maple syrup. And in autumn the spectacular orange and yellow hues of sugar maples ignite our eastern woodlands.

Norway maple doesn’t offer maple syrup and its autumn colour, though sometimes a vibrant yellow, cannot compete with our native sugar maple. Moreover, Norway maple as a non-native, does not support insects and, in turn, songbirds nearly as well as a sugar maple does. In recent ice storms Norway maple has also demonstrated its vulnerability to breakage. As if all this wasn’t enough, Norway maple, through its copious seed production, is invading woodlots and ravines adjacent to the urban areas where it is grown. It is, in fact, one of our most dreaded invasives, right up there with buckthorn and phragmites.

Please be aware of the perils in purchasing a maple. Many people, with excellent intentions, arrive at a nursery to purchase “Canada’s tree”. They often end up with a Norway maple instead. This because many nurseries don’t market Norway maples as Norway maples. Instead, they employ a variety of euphemisms to lure you to the dark side. These include “Royal Red”, “Emerald Queen” and “Crimson King”. Who could resist trees with such grandiose names? Further, though the name tags may include the Norway maple’s scientific name Acer platanoides, nurseries know that most people will pay scant attention to that.  

So, here’s hoping you’ll arrive at a nursery armed with the knowledge to come home with a genuine Canadian sugar maple, a tree of storied history and uncommon beauty.

Pagoda Dogwood

Cornus Alternifolia

Pagoda dogwood is one of the few small native trees suitable for the urban environment. Fortunately, with its tiered branching habit and red-stemmed fruit, it also has great aesthetic appeal.

Virtues: Pagoda dogwood grows quickly. As mentioned above, a primary virtue is its small size, making it suitable for even postage stamp urban yards. It also grows well in shade, so is an excellent choice for planting under larger trees. Pagoda dogwood offers cream-coloured flowers on its tiered branches in spring. These are followed by dark blue fruit. Its autumn leaves can be rich purple-red.

Wildlife value: Pagoda dogwood flowers are abuzz with bees in early spring. The fruit is relished by birds, which in suburbia include robins and cardinals.

Needs: This tree is probably best situated in shade or semi-shade as these are the conditions where it is found in the wild. Shade will also enhance the tiered effect of its branches. Pagoda dogwood can thrive in sun as well but will need supplemental water in dry spells.

Local examples: Pagoda dogwood is abundant in Halton Hills, where it thrives in the understory of woodlands and along roadsides and hedgerows. A splendid urban example grows on Campbell Gate between Prince Charles Rd and Mountainview Road in Georgetown.

Pawpaw

Asimina triloba

A small tree for anyone who treasures the unconventional. Pawpaws, with large glossy leaves and wonderfully quirky flowers and fruit, look like they’ve been lifted from a Central American rainforest. That tropical appearance is no coincidence. Most of pawpaw’s relatives do grow thousands of kilometres to the south. This is another very rare Ontario tree with only scattered occurrences in our Carolinian Zone. Speculation has it that First Nations peoples planted it in Ontario to avail themselves of its large edible fruit.

Virtues: Like cucumber magnolia, part of pawpaw’s appeal is its rarity in this province. It deserves to be better known and more widely planted. Its tropical leaves, mentioned above, are a notable aesthetic feature. Pretty maroon flowers in spring are followed by large irregularly shaped fruit. This fruit is edible. Some rave about the taste of its custard-like flesh, others turn their noses up at it. It doesn’t help that multiple large shiny seeds are embedded in each fruit. Despite the varying critiques of the fruit, orchardists in Ontario and elsewhere are looking at its commercial potential. Another pawpaw plus is its small size, suitable for typical suburban lots. It is also shade tolerant, growing as an understory tree in the wild.

Wildlife Value: Unsurprisingly mammals other than humans eat pawpaw fruit. These include bears, racoons and opossums. But, in common with Kentucky coffee tree seed pods, pawpaw fruit may have lost its primary dispersal agents long ago. Connie Barlow in “Ghosts of Evolution” proposes that the large size of pawpaw fruit and its large tough seeds originally evolved to be eaten by big animals – really big animals like mammoths and mastodons. These megafauna disappeared from our neighbourhoods only a quick blink ago in geological time. The theory goes that pawpaw has persisted through sub-optimal dispersal ever since and that accounts for its spotty distribution. If true, people could now be the pawpaw’s main (essential?) benefactors.

Needs: Despite its southerly distribution in nature, pawpaw is hardy in Halton Hills. It does appreciate partial shade and is not recommended for planting in full sun. This is a wonderful small tree but be prepared for suckering at the base of the main trunk. This is one of the ways pawpaws expand their footprint in the wild. If suckering becomes a concern the sprouts can easily be controlled by mowing.

Local Examples: We know of pawpaws growing on private yards in Halton Hills but not on any public properties other than the ones recently planted at the arboretum. Two long-lived pawpaws grow in a backyard in Inglewood demonstrating hardiness in this area. The University of Guelph Arboretum has several fruit-bearing specimens, and a large pawpaw patch grows at the Royal Botanical Gardens Arboretum in Hamilton.   

 

Red Oak and Pin Oak

Quercus rubra and Quercus palustris

Why two oaks? Though red oak was requested for the arboretum, we discovered after the planting that a similar sharp-lobed leaved species called pin oak was installed. This is not necessarily a negative. Pin oak is a native and has some fine attributes. However, our recommendation for urban planting in Halton Hills would be the versatile red oak. (We hope to have a red oak planted at the arboretum soon.)

Pin oak is a rare species in Ontario, found primarily in Niagara Region and Essex County. They have more exacting soil requirements than red oaks. Their species name “palustris” means “marshy” or “swampy”, providing a clue as to where this tree likes to grow in nature. Although there is some natural variation in the species, most pin oaks like some acid in the soils they grow in. Most Halton Hills soils are neutral to slightly alkaline pH.

Red oak on the other hand is simply one of the most versatile trees we have, growing everywhere in Halton Hills and throughout southern Ontario. It can thrive in all soil types and is impervious to environmental conditions, growing in forests and as solitary specimens in agricultural areas.

Virtues: Both species are beautiful. Both grow into strong, long-lived trees. Both offer fine russet foliage colour in autumn. Pin oak is unique among oaks for its pyramidal shape in its first few decades. Red oak grows into a statuesque muscular tree that will dominate a neighbourhood for many generations. It is a standout in our urban or natural environments.

Wildlife Value: All oaks are prime food for native caterpillars which our songbirds appreciate. The best place to look for the incomparable scarlet tanagers is among oaks, where the adults gather food for their young. All oaks also produce acorns, a valuable food source for birds like blue jays and red-bellied woodpeckers and for small mammals.

Needs: Both pin oak and red oak will appreciate as much sun as you can offer. As mentioned, pin oak is more particular to soil type (see above). Red oak on the other hand will thrive just about anywhere. All oaks are attacked by LDD moths. (But so are many other tree species!) Even a major infestation of LDD caterpillars is unlikely to harm a mature tree, but with smaller specimens some control is advisable.

Local examples: Red oak is one of the most common Halton Hill’s trees. Big and bold, they are easily found in area woodlands. Their abundance becomes evident in the autumn. After other deciduous trees have lost their leaves red oaks stubbornly hold on to theirs for a month or more. Mature urban red oaks can be found at the Georgetown Fairgrounds and Greenwood Cemetery in Georgetown.

Pin oaks have been planted sparingly by urban forestry departments. Two fine pyramidal young specimens can be seen along the bike path behind the Gellert Centre in Georgetown. Some boulevard plantings of pin oak in this area have not fared as well, demonstrating a yellowing of the leaves called chlorosis, caused by insufficient iron in alkaline soils.

Special Note: To reiterate, our recommendation is that you select red oak for an urban yard in this area, not pin oak. Red oak is also much easier to find at area nurseries.

Redbud

Cercis canadensis

Despite the species name (canadensis) this tree qualifies as native to Ontario by only the slimmest of margins. Though widespread in the eastern U.S. there is only a single record from Canada, at the southernmost extremity of the southernmost inhabited piece of real estate in the nation: Pelee Island. The speculative origin story for this tree is interesting. It has been proposed that it grew from seed blown across Lake Erie ice from Ohio. Regardless of its status in Ontario this small tree should be welcomed as a unique addition to our flora. It is lovely in the spring when its branches are festooned with abundant purple (not red!) flowers.

Virtues: The flowers as mentioned are lovely. The heart-shaped leaves recommend this tree as well and the small size of redbud makes it suitable for suburban yards.  

Wildlife value: Some species of bees enjoy the nectar of redbud flowers and the seeds are consumed by chickadees and cardinals during the winter. The intriguing and harmless leaf-cutting bees provision their nests with circular leaf cuts from this tree.

Needs: In nature, this tree usually grows in the understory of open woodlands. There it assumes an airy branching structure that beautifully expresses the blossoms. So this is a tree that can be grown in the shade of other, larger trees. It will also thrive in the open where it will assume a denser branching structure. Soon after planting it may suffer some winter dieback at the ends of its branches, but this fast-growing tree recovers quickly. Mature specimens in Halton Hills indicate it is hardy here.

Local examples: Redbud remains an uncommon tree in urban plantings in Acton and Georgetown, although this is changing. Great examples of open grown redbuds can be found on Carole Street in Georgetown and in Norval on the north side of Highway 7 on the east side of the Credit River.

River Birch

Betula nigra

In the arboretum is a species of birch in clump form that originates south of the border. This is river birch, selected for the arboretum because of its greater resilience than our native white birch to a pest called bronze birch borer. Being an eastern North American native, river birch serves the same ecological functions as native Ontario birch species, including supporting native caterpillars.

Virtues: River birch has wonderful exfoliating bark. It makes a fine specimen tree and can tolerate clay soils. Sun is recommended, but river birch can be planted close to other trees that cast light shade.

Wildlife Value: Like all birches, river birch is a wonderful caterpillar food plant. And as has already been made clear, the native caterpillars seldom harm our trees but are crucial to the well being of songbirds.

Needs: River birch will appreciate lots of water until it establishes a deep root system. Even then, occasional watering during droughts is recommended.

Local Examples: Some river birch clumps grace suburban yards in Acton and Georgetown.  

Shagbark Hickory

Carya Ovata

To tap into the metaphor comparing trees to people, Shagbark Hickory is a true individual. Its namesake shaggy bark sets it apart from every other native tree except the closely related Shellbark Hickory. It produces flavourful, nutritious nuts when mature. Its range in Canada closely aligns with the lands adjacent to the lower Great Lakes and the St. Lawrence and Ottawa Rivers, supporting speculation that Shagbark Hickory was planted by First Nation’s peoples along their trading routes so they could include the nuts in their diets.

Virtues: An adaptable tree, able to thrive in dry to moist soils. Year-round appeal of beautiful exfoliating bark. Attractive yellow autumn foliage.

Wildlife Value: The nuts are sought after by many small mammals and birds. Its foliage feeds 200 species of caterpillars.

Needs: Lots of water initially, but drought tolerant after establishment. Give it as much sun as possible. In the generally dry soils of suburbia this is a slow growing tree – an asset, or a liability according to your needs. 

Local examples: A beautiful Shagbark Hickory grows on the east side of Clayhill Road north of Glen Williams just beyond Fallbrook Road. Many grow along the Great Esker Trail north of Georgetown and at Terra Cotta Conservation Area.

Sugar Maple

Acer saccharum

Is there a more beloved tree than this one in Canada? Though the leaf on our flag is not a strict representation of a sugar maple leaf— some suggest it looks more like a leaf of the invasive Norway maple – the maple leaf remains a cherished Canadian symbol. And, of course, the maple leaf is the logo of a beloved, if perennially woeful, Toronto hockey team.

Sugar maples provide the sap we tap as a treasured rite of spring in the eastern half of this country. Maple syrup production is a multi-million dollar industry centred on Quebec.

In the fall sugar maples turn various shades of red, orange and yellow, providing much of the autumn splendor that graces our deciduous woodlands.

Regrettably there is a nefarious imposter maple that masquerades as our beloved sugar maple and this tree needs to be outed. This is the Norway maple (mentioned above). To most casual observers Norway maples are indistinguishable from sugar maples and therein lies the problem. Nurseries usually don’t identify them as Norway maples, instead they gussy them up with names like “Crimson King” and “Emerald Queen”. Why should we learn the difference between Norway and Sugar? Many reasons, but first among them is that Norway maples are one of our most challenging invasive species, displacing native trees in our woodlands. Norway maples don’t produce the sugar rich sap that sugar maples do, nor do they offer the vibrant range of warm colours that sugar maples do in the fall.

Virtues of sugar maples: Maple syrup comes from these trees. The leaf colour in autumn is spectacular.

Wildlife Value:  It’s foliage feeds over 200 species of caterpillars. Its seeds and buds are eaten by birds and small mammals.

Needs: Sugar maple can tolerate shade especially when young but for the full expression of its beauty give it some sun. This is a species that lives harmoniously with other species like black cherry, basswood and oaks in our local forests, so could be planted in close proximity to other trees. It grows well in various soil types but should not be planted close to busy streets because of its intolerance of salt.

Local examples: The most common tree in our local deciduous or mixed woodlands. Many large specimens grace the older sections of Acton and Georgetown. Regrettably most of the boulevard maples in these communities are Norway maples.

Tulip Tree

Liriodendron tulipifera

A magnificent tree of our Carolinian forests in Ontario, rivalling white pine as our tallest native tree. It is certainly our tallest deciduous tree. Other tulip tree superlatives include its ancient lineage. Fossils reveal that that they evolved during the time of the dinosaurs. In natural settings tulip trees are most common on moist sandy loams but can grow well on clays in suburbia. Tulip trees are another species that is now receiving more attention from urban forestry departments. Despite being confined in nature to Ontario’s deep south, tulip trees are now being planted well north of their native range

 Virtues: Tulip trees offer lovely deep green leaves that, with a little imagination can be construed as tulip shaped. The form of young trees is roughly pyramidal. Fast growing, they shoot up straight and true, as they reach for the sky. The large yellow-orange flowers are lovely but sometimes high and out of reach. The autumn foliage colour is bright yellow.

Wildlife value: A favourite food plant of the caterpillars of tiger swallowtails, one of our loveliest butterfly species. Bees enjoy the flowers.  

Needs: Tulip tree appreciates sun and would benefit from lots of water in its early years. Its large ultimate size needs to be considered but there is certainly room for a tulip tree in large yards.

Local Examples: A very old specimen, only now beginning to decline, can be seen along Guelph Street in Georgetown roughly across from Georgetown High School. Younger, vigorous tulip trees, already producing their lovely blossoms, grow at the Old Seedhouse Garden in Georgetown.

White Oak

Quercus alba

In their maturity these trees are truly spectacular with large, muscular branches. Their longevity is legendary. One at Bronte Creek Provincial Park germinated in 1685. Fencing protects this 1.6 metre diameter behemoth from people and equipment that could compact the soil around its base. Though common in south Halton, (Oakville was named for its white oaks), this species is rare in Halton Hills. It takes a tree connoisseur to distinguish white oaks from burr oaks, but a look at a good field guide will reveal the differences. Both species are in the White Oak Group characterized by leaves with rounded lobes and acorns that take two years to mature. The Red Oak Group contains species that have leaves with pointed lobes and acorns that take only one season to mature.

Virtues: A lovely, refined tree in its maturity. Splendid vermillion foliage in the fall. Its sturdy branches would give a treehouse great support. (Of course, you may have to wait a century or so to build it!)

Wildlife Value: Like its close relative the burr oak, this species is at the pinnacle of wildlife value among our native trees. Its foliage feeds hundreds of different species of caterpillars and hence, birds. As mentioned in the introduction these caterpillars almost never hurt the tree (except for the invasive LDD caterpillars). Witness the fact that the Bronte Creek white oak has fed caterpillars for over 330 years while remaining robust health.

White oak acorns are also choice food for birds and small mammals.

Needs: To be candid, the scarcity of white oaks in Halton Hills suggests that our soil may not be quite to its liking. Some texts state a preference for acid soils. The white oak in the arboretum will tell us, as years go by, whether it likes the conditions here. If you have the space and money to take a chance on this species, your reward, if it thrives, would be a tree of uncommon beauty.

Local examples: As mentioned, white oaks are rare in Halton Hills and at the time of writing we were unaware of any large white oaks growing in Acton or Georgetown proper. The few naturally growing oaks in our town grow at Terra Cotta Conservation Area and along the Credit River between the River Road Bridge and Norval. White oaks are abundant at Cootes Paradise in Hamilton and in the uplands near Oakville and Bronte Creeks in south Halton.

White Pine

Pinus strobus

This is Ontario’s official tree and with good reason. Its majestic spires rise above all other trees in the forests of eastern Canada. This is the iconic wind-blown pine of Group of Seven paintings. In the early days of colonization, particularly tall, straight white pines were claimed by the British Crown for use as masts by the British navy.

Virtues: Beautiful year-round appeal of its form and foliage. Relatively fast growth. Adaptable to a variety of soil types.

Wildlife Value: The cones provide seed for birds and small mammals. When mature, a variety of birds nest in its dense foliage. A favourite nesting and roosting tree for owls.

Needs: White Pine will grow well in any soils but should not be planted adjacent to roads because of its intolerance of salt. Because of its ultimate size, probably best planted in larger yards.

Local examples: Many can be found in yards in Halton Hills, especially in the older sections of Acton and Georgetown. Beautiful mature specimens grow at Greenwood Cemetery in Georgetown. Common throughout forested areas in Halton Region.

Native Shrubs

American Hazelnut

Corylus americana

This large shrub is a good complement to a naturalized garden, producing edible nuts in the autumn that are sought out by a vast array of birds and animals. It is tolerant of all manner of soils and will grow well in part shade or sun. This is another shrub that in most suburban gardens will need regular pruning to encourage a more dense, compact structure. Also, like many shrubs, it spreads by suckering, a situation easily controlled, if desired, by a lawn mower. Its fall colour is variable but can be a rich yellow.

Black Chokeberry

Aronia melanocarpa

n the wild this is a shrub of wetlands, but it can grow well in the dryer soils of suburbia. It produces small white flowers, followed by black fruit enjoyed by birds but its main appeal is lovely red autumn foliage.  Black Chokeberry is a small shrub, eventually reaching a height of two metres or so.

Bush Honeysuckle

Diervilla Ionicera

Bush Honeysuckle is a dense low mounding shrub with arching branches. The attractive foliage is often tinged with burgundy. Pretty yellow/orange flowers that appeal to bumblebees are produced in spring. This shrub is happy in a range of soil types and will grow in full shade, or sun. It would be a good choice to fill space beneath a taller shrub.  Bush Honeysuckle produces suckers, but if grown adjacent to lawn, this habit can be easily controlled by mowing.

Chokecherry

Prunus Virginiana

This quick growing shrub is abundant in Halton Hills, spread by the birds that adore its fruit. Chokecherry is versatile and can grow in shade or sun. The pleasantly scented flowers are more prolific in sun, however. Like all cherries, its foliage feeds caterpillars, which, in turn feed birds. A caution is that it is prone to black knot, a fungal disease that is expressed by black lumps on the twigs. Though seldom fatal, it does affect the appearance of the shrub. Chokecherry also suckers readily, requiring vigilance to keep it in bounds. These problems suggest placement in a wilder part of the urban garden.

 

Common Ninebark

Physocarpus oppullifollus

An appealing feature of this quick growing multi-stemmed shrub are profuse springtime flowers that attract a multitude of pollinators. Common Ninebark is easy to grow but appreciates as much sun as you can offer. The burgundy seed heads following the flowers extend the appeal of this shrub. Regular pruning will help manage ninebark’s sprawling habit. Commonly available in nurseries are more refined Common Ninebark selections with maroon foliage. Despite this colour switch, their flowers are also highly valued by pollinators. And sometimes, standard (single-stemmed) varieties of these maroon-leaved ninebarks are offered. They are lovely.

American Highbush Cranberry

Viburnum opulus var americana

Wonderful flowers bedeck this large shrub in spring, followed by brilliant red berries. This is a multi-stemmed shrub that will appreciate a little extra moisture in your garden. Though the berries might tempt you to taste, this is not advised. The taste of highbush cranberries is quite repellent. In fact, birds typically leave them until late winter and then resort to them after more palatable berries have been consumed. This means we can enjoy the fruit through much of the winter season. And quite likely, having distasteful fruit might work in favour of the highbush cranberry. When the birds finally do get around to consuming it, the ground is beginning to thaw and will soon be ready for the growth of seedlings. One caution is to look for Viburnum triloba or Viburnum opulus var americana at nurseries. If a highbush cranberry is simply labeled Viburnum opulus it is the European version. This non-native is not thought to be as valuable for wildlife. Another caution is that the invasive viburnum leaf beetle that likely came here on the leaves of the European High Bush Cranberry, can quickly defoliate our native species. Be on the lookout for their larvae and be ready to spray with soap and water.

Nannyberry

Viburnum lentago

Nannyberry is ultimately a large shrub or small tree reaching 5 metres or so. It can be grown in partial shade but for a significant display of its creamy white flowers, sun is necessary. These flowers are followed by dark blue fruit that feeds birds and small mammals. Nannyberry thrives in a variety of soil types. Like most other shrubs it will benefit from some extra water for a few years after planting. In the fall the foliage turns an attractive red-purple colour. Left to its own devices Nannyberry will grow as a multi-stemmed shrub, but it can be trained to a single stem by pruning

New Jersey Tea

Ceanothus americanus

New Jersey Tea acquired its name long ago when its leaves were used as a substitute for expensive imported tea leaves from the orient. Some people still use it for this purpose, though you’d have to grow several of these small shrubs to reap an appreciable harvest! An attribute (or liability depending on your point of view) is this small size. New Jersey Tea is unlikely to exceed one metre in height. If planted in full sun the white frothy flowers are pretty but short of spectacular. They do attract bees and butterflies. Of interest is that New Jersey Tea leaves are the only food source for the caterpillars of an endangered Ontario butterfly called the Mottled Duskywing. There are colonies of this butterfly in south Halton Region. Perhaps if more of us plant New Jersey Tea in Halton Hills, they will be able to colonize our area. After being established on any well-drained soil, New Jersey Tea is impervious to drought. It can sucker, but not aggressively enough to cause much concern.

Red Osler Dogwood

Cornus sericea

In winter, wild Red Osier Dogwood paints low lying areas in Halton Hills a joyful red. The red stems of this plant have made it a staple in the nursery trade. Horticultural varieties include some selected for a smaller ultimate size or a greater intensity of colour. Even yellow-stemmed Red Osiers are available. The typical Red Osier Dogwoods grow over two metres in height and, as indicated by their species name, “stolonifera”, spread by stolons or runners. Regular pruning will encourage bushier growth and brighter colour. Red Osier Dogwoods produce modest white flowers in spring and white fruit that feeds birds. Though they grow in moist areas in the wild they are easy going in suburban yards, accepting various soils and degrees of shade.

Serviceberry

Amelanchier species

Serviceberries range in size from small shrubs to small trees. Various species are offered in local nurseries. All are versatile additions to home landscaping because of their beauty and small size.

Virtues: Serviceberries have been tagged with numerous names across North America. These include Juneberry, Saskatoon, Shadbush and Sarvisberry. The vast range of this genus from high in our Northwest Territories to deep in the American south, speaks to its adaptability. There are serviceberries available to suit just about any environmental condition. Like pagoda dogwoods, serviceberries play a salutary small tree role in urban settings. They offer splendid white blossoms in spring and plentiful fruit in the summer. Serviceberries are related to apples, cherries and plums and the fruit of most species is just as delectable. It can be race to beat the birds to the harvest though.

Wildlife Value: As mentioned above, birds love serviceberry fruit. In town, robins get most of it, but the dapper cedar waxwings will often find it in their nomadic wanderings.

Needs: Serviceberry will flower and fruit best in full sun. After establishment it will shrug off drought conditions.

Local Examples: The versatility of serviceberry has made it a go-to plant for urban landscaping. Many have been planted along boulevards and on commercial properties in recent years. A drive through Acton or Georgetown during its blooming season in early spring will reveal many of these. In natural settings serviceberry lights up woodland edges. It can also thrive in the open in soils that are avoided by other trees. Serviceberries grow on eroded clay soils in the Terra Cotta area for example.

Smooth Rose

Flosa blanda

A virtue of this wild rose species is its lack of thorns on its upper branches – hence its name. This is a good species for a wilder section of an urban garden, but please don’t expect the opulent blooms of ornamental roses. The blossoms of Smooth Rose and, in fact, all our native roses, are simple pink flowers that bloom in spring. They are followed by bright red rose hips. The flowers feed pollinators and the hips are choice food for birds and small mammals. All our roses sucker but simple mowing around the periphery of your rose bush will keep it contained, if that is your goal.

Spicebush

Lindera benzoin

Pinch a spicebush leaf, bring it to your nose and revel in one of the most delightful aromas in the natural world. The scent is intoxicating. Spicebush grows sparingly in moist conditions in Halton Hills. A little further south it is an abundant presence in the woods and wetland margins. Despite this habitat preference it can grow perfectly well in suburbia if given a little shade and supplemental watering in its first few years. Yellow blossoms appear before the leaves in early spring. Think Forsythia but not as garish. On female plants these flowers turn into glossy red fruit – if a male is nearby. Spicebush belongs to the substantial minority of plants that are “dioecious”: each plant is either male or female. Males don’t fruit. This situation requires the purchase of two or more plants if you want the fruit, complicated by the fact that male and female plants are seldom, if ever, identified to gender in nurseries. Spicebush is another shrub that you may choose to periodically prune but in natural gardens is fine left untouched. It grows to a maximum height of two metres or so. One other quality of note is the rich yellow of Spicebush foliage in the fall.

St. John's Wort

Hypercum kalmlanum

This is small free-flowering shrub when grown in sun. The showy yellow flowers are its greatest appeal. Pollinators like them too. The growth habit is restrained and can be accommodated even in small gardens. A suitable shrub for even more formal garden settings with its neat, rounded habit. St. John’s Wort isn’t particular about soil type and can tolerate dry conditions after it becomes established. A cultivar with blue-green foliage is available.

Winterberry

Ilex verticillata

Our native holly. Though winterberry doesn’t have evergreen leaves, it does produce the vivid berries that we associate with holly in the festive season. These berries on open grown winterberry shrubs can be produced in great profusion. They are nothing short of spectacular at their height in November. A great local spot to see them is at Hwy 25 and 22nd Sideroad south of Acton. As with all hollies, male and female flowers occur on separate plants. Female hollies must have a male in the vicinity for berry production to occur. This shrub is well suited to moist or wet areas in full sun. It’s gangly nature outside of the fruiting season suggests placement in a wilder section of your property.

Witch Hazel

Hamamelis vernalis

Witch Hazel is unique among our native trees and shrubs in that it blooms in the fall. Wispy yellow flowers persist long after it drops its leaves, often through November or even into December. In the wild, Witch Hazel usually grows on dry to moist soils along woodland verges where it enjoys substantial sun exposure. In these settings it is usually a lanky shrub with branches arching towards the sunlit side of the forest edge. But if permitted full sun in a suburban setting it will grow into a more pleasing, rounded form. The full sun will also spur it to produce abundant flowers. As with most shrubs Witch Hazel will benefit from pruning as it grows, in part to manage the multiple stems it often produces. You may choose to channel growth into one main stem or a few stems. Don’t let this minor challenge dissuade you from planting it. Where happy in an open urban setting, Witch Hazel can become a truly lovely accent in the autumn.

THE RIGHT TREE
Planting Tips

Plant the right tree in the right place by knowing the best planting conditions for the tree you want. Consider sun/shade; soil conditions; proximity to buildings, roads and utilities; the height and crown of the mature tree and aesthetics. You want your tree to thrive!

For help on choosing the right tree for you, check out the Credit Valley Conservation’s DIY Tree Planting Guide.

THE RIGHT TREE
Planting Tips

Plant the right tree in the right place by knowing the best planting conditions for the tree you want. Consider sun/shade; soil conditions; proximity to buildings, roads and utilities; the height and crown of the mature tree and aesthetics. You want your tree to thrive!

For help on choosing the right tree for you, check out the Credit Valley Conservation’s DIY Tree Planting Guide.

65,000 TREES FOR HALTON HILLS

30 Albert Street

Halton Hills, ON. L7G 2B1

treesforhaltonhills@gmail.ca