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Species of the Month: Winterberry Holly (Ilex verticillata)

This uniquely red plant stands out amongst many of the other species that we grow at St. Williams Nursery & Ecology Centre. For one, this plant produces a vibrant red berry (a image of: winterberry holly (Ilex verticillata)favourite of over 40 species of birds) that is sure to liven up your garden. Plus, the Winterberry Holly’s (Ilex verticillata) berries are particularly showy and remain present throughout winter. A great reminder of summer gardening during the snowy Ontario winter. Winterberry Holly stands tall with a height and spread of 3-12” (1-3.7 metres). Not only are the berries persistent throughout the winter, but their shade of red is a beautiful compliment to a white snowy landscape. The plant thrives in full sun to partly shady areas. It’s slow-growing in medium to wet conditions and tolerates wet soil, clay soil and air pollution.

Not Just a Favourite of Humans

One of the coolest thing about Winterberry Holly (Ilex verticillata) is how much wildlife like to dine on the berries that the plant produces. Like we mentioned above, the berries are devoured by over 40 species of birds, including songbirds, winter waterfowl, and game birds. The plant is a favourite of small mammals who enjoy the berries and seeds produced by the plant as well. If you’re looking for a real Disney scene in your back yard, then we can’t image of: Winterberry Holly (Ilex verticillata)recommend Winterberry Holly strongly enough. Not only will the plant add a beautiful wintery red to your garden, but you can feel good about planting it, knowing that you’re providing a meal to small critters, and our feathered friends.

We know you’ll love Winterberry Holly (Ilex verticillata), as it’s relatively easily grown, and has a good tolerance for poorly drained soils. Keep in mind, however, that only fertilized flowers on female plants will produce the attractive red berries that are the signature of the species. Generally, one male Winterberry will be sufficient in pollinating 6-10 female plants, and once they’ve bloomed, the berries will produce a lovely red against the plant’s already greenish white leaves – the perfect colour for February, the month of love.

Want to get the most out of your Winterberry Holly? Here are some tips:

  • Power in numbers! Winterberry Holly makes a stunning mass shrub planting.
  • A great shrub to use around retention ponds or runoff ditches.
  • When choosing suitable companions, think evergreen in the winter. A collection of Winterberry Holly backed by a line of White Cedar, Pine, or Spruce can make a stunning contrast. In the summer, consider some herbaceous wildflowers to complement Ilex verticillata. Echinecea pallida and Symphiotrichum oolentangeinse make wonderful companion species.

To learn more about Winterberry Holly, check out, and don’t forget to follow us on Facebook and Twitter to see features like ‘Fast Facts’ and new blog posts like this one here!

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Green Roofs

One of the cooler trends we’ve seen lately are green roofs in big cities. Alright, green roofs – that is a roof that is image of: a green roofmostly or completely covered in vegetation – have been around forever, especially in European countries. Recently though, larger, metropolitan areas closer to home have been looking at green roofs as a way to deal with certain issues, like hunger and climate change. While the practice of green roofs has been (pleasantly) on the rise lately, there is one project in particular that is worth keeping an eye on. Rye’s Home Grown is a project that has been in the works at Ryerson University since 2010, focusing on a series of experimental gardens intended to raise awareness about food security issues.

The original intention of Rye’s Home Grown in 2010 was to place moveable planters in the middle of Gould Street, which runs through the heart of Ryerson’s campus. Due to construction concerns, this idea was eventually scrapped in favour of some unused spots around the campus. Eventually the project grew, and a larger space was required. By 2013, the project expanded to utilize the green roof that Ryerson’s engineering building had been using to save energy costs since 2004.

Why is This Important

Since adding this project, dedicated to creating a closed-loop food supply system (a farming practice that recycles all nutrients and organic matter material back to the soil that it grew in) to Ryerson’s active green roof, the students and faculty working on the project have converted ~10,000sqft. Of the rooftop into fruit and vegetable gardens. This produce is then sold at Ryerson’s weekly farmer’s market, as well as to campus food services. The profits from the produce sales are then put back into the project in order to keep up and expand the ever-growing garden. With a total current enrollment of 36,374 hungry mouths to feed, there would be a necessity for a lot of otherwise-sourced vegetables without the help of this burgeoning botanical buffet.

The benefits of a green roof are pretty clear. Even before Rye’s Home Grown was added to the University’s green roof, the campus was already using it to reduce the building’s energy costs. Since using the green roof space to grow vegetation for their meal programs, they’ve also been cutting down on costs necessary to bring in outside food. Now extrapolate that to the rest of Toronto – and other metropolitan cities for that matter. There is so much underutilized space on the tops of office buildings, and apartments that could be harnessed for the production of native Ontario vegetation.

image of: green roofsVegetation production isn’t the only benefit of a green roof. We mentioned that the Ryerson engineering building has been using their green roof as a way to cut down on energy costs for fourteen years now. That’s huge! Green roofs work to reduce the heat flux through the roof, and as a result, buildings require less energy to be cooled. A 2006 University of Michigan study gleaned from claims that while a green roof installed on a 21,000 square foot surface would cost roughly $129,000 more than a conventional roof, but would save around $200,000 over its lifetime. Close to two-thirds of these savings are attributed to reduced energy requirements! Additionally, green roofs are a great way to improve storm-water management. This is another major benefit, since massive water runoff in areas with impervious roofs can lead to flooding and water damage. Not only are green roofs a great leap forward in solving problems like the energy crisis, and hunger, but a green roof with the right plants can also be a destination for hungry bees and other pollinators – a monumental benefit in an age where the population of bees is dangerously low.

For more on environmentally friendly projects, as well as profiles and interesting information about the beautiful plants that we grow, visit, and don’t forget to follow us on Facebook and Twitter for features like the monthly ‘Did You Know’ and ‘Fast Facts’.

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It’s a new month, and a new year. That means that it’s time to look to another beautiful plant for our Species of the Month! This January we’ll be focusing on the beautifully blue Virginia Bluebells (Mertensia virginica)

Physical Traits

This pretty little plant can get to be up to 0.6 metres (2 feet) tall and can spread out to about 0.45 metres (1.5 feet) wide. Mertensia virginica may not take up a terrifically large amount of space in your garden, but it’s just the thing to add a splash of light blue colour to your garden. Because of its low stature, it can often be found covering the woodland floor with a stunning blue flower shortly into the first weeks of spring. Like most spring ephemerals, the plant will show for about a month before it begins to die back to the ground. Because of its showy nature, and early bloom time, many native plant enthusiasts turn to Virginia Bluebells as an entry level wildflower to get people excited about native plants.

The Virginia Bluebells (Mertensia virginica) is fairly easy-going (or ‘easy-growing’ as the case may be) as it thrives in partial or full shade, which is perfect for the less sunny months of the year. This species requires a medium amount of water and, when fully developed, will bloom into a beautiful shade of baby blue, just like its name implies. Mertensia virginca tolerates rabbits and black walnut.


As mentioned above, Virginia Bluebells are easily grown in light to full shade in moist areas with rich, loamy soils. It develops quite quickly during spring after the danger of hard frost has passed. Its foliage will die down by mid-summer

Garden Uses

Best assembled and left undisturbed in moist, shady woodland, wildflower or native plant gardens.

image of: virginia bluebells (mertensia virginica)It is important not to disturb the plant, as once it’s established, you run the risk of losing a season of flowering, or even killing the plant. Once the flower is in bloom though, it’s unique, light blue colour is sure to brighten up your garden. This plant combines well with False Solomon’s Seal (Maianthemum racemosum), Spicebush (Lindera benzoin), Common Boneset (Eupatorium perfoliatum), or Large-Leaved Aster (Eurybia macrophylla).

It may be cold outside right now, but the Virginia Bluebells are just the plant to remind us that brighter days are ahead. Since this beautiful plant starts to bloom in early spring (early to mid April), it’s a natural indicator that the weather is about to warm up, and before long gardening season will be in full swing.

Mertensia virginica are a favourite of bees, as well as several other types of pollinators, such as: butterflies, and hummingbirds. So, you can feel good about giving some wildlife a place to eat after a long, chilly winter.

For more on the Virginia Bluebells and other species that we grow here at St. Williams, be sure to visit We’ve got more on Mertensia virginica coming out this month too, so make sure you follow us on Facebook and Twitter so you don’t miss out on a thing!

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As we enter 2018, I am reflecting on our goal to help restore Ontario’s native biodiversity by re-establishing appropriate native plant communities with wild-type genetics back to degraded landscapes in the province.  It is a good time to evaluate our progress and look ahead to challenges and opportunities that lay ahead with respect to achieving this purpose.

In 2017, St Williams Nursery and Ecology Centre (SWNEC) continued its role as a quiet and dedicated leader in biodiversity conservation in Ontario by ensuring the continued availability of high quality source-identified plants and seed, including almost 400 species of plants native to the province.  These plants end up on restoration projects on public and private lands, in conservation areas, provincial and national parks, in the countryside and in towns and cities across the province.  We also continued to provide ecological restoration support on major projects including at Westminster Ponds ESA in London, naturalization projects in Mississauga, Toronto, Ottawa and Sudbury, Durham Region, and in Bruce Peninsula National Park, and for mine tailings rehabilitation in Kapuskasing.

In 2017, we made significant advances in developing our Native Seed Network Database that will allow us to more efficiently track locations of native plant material sources, collected by our team of dedicated scientists and technicians, and to increase our ability to work with committed conservation partners.  Source tracking and verification is a critical component to ensuring effective, legitimate conservation and restoration of our native biodiversity but is an increased cost not appreciated by most.

Unfortunately, we may be losing the fight to protect and conserve biodiversity given the extent of habitat loss especially in southern Ontario and the ongoing impact of invasive species.  While it may seem significant, 400 species is a small fraction of the 3400 native species indigenous to Ontario, many of which need to be protected and restored to degraded landscapes.  Major challenges to successful conservation efforts include lack of awareness and lack of effective funding for meaningful on-the-ground efforts like coordinated seed collection from wild plant populations, which is essential to this effort.  In many cases our conservation programs and organizations in the province remain uncoordinated and fail to ensure effective biodiversity conservation.  The broader nursery and landscape industry in the province continues as a whole to be a negative influence rather than a conservation force for biodiversity in the province.  It is time for a serious change in our behaviours and efforts to restore native biodiversity if we are going to be successful.   It is time for government and conservation organizations alike, to demonstrate leadership to effect meaningful conservation at the scale necessary to reverse the trend of biodiversity loss.

I am encouraged by organizations such as the World Wildlife Fund and Carolinian Canada who now are recognizing the importance of restoring habitat using native plant communities with appropriate wild type genetics as critical component in our fight to conserve Ontario’s natural biodiversity.  Clearly this effort will require substantially more resources and commitment than has been given to date.  I can give you my assurance that SWNEC remains committed to this important cause, but it will require the collective efforts of existing and new champions, and more effective conservation partnerships if we are to have a real chance of conserving and restoring Ontario’s native biodiversity.


Yours in conservation,

Allan Arthur, M.Sc.

President, Sr Ecologist

St Williams Nursery and Ecology Centre

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The White Pine (Pinus strobus) is a large pine tree that is native to eastern North America.  This tree originally Image of: White Pinecovered much of north-central and north-eastern North America however, much of this forest cover was lost due to extensive logging operations.  It is a very important tree to these areas being the Provincial tree of Ontario as well as the State Tree of both Maine and Michigan.  You will also recognize the classic wind-swept look of the White Pine from many famous Ontario artists paintings including the renowned Group of Seven artists.

Eastern White Pine grows rapidly and is long lived.  Mature trees are often 200-250 years old, and some trees have even been documented to live for over 400 years!

Noteworthy Characteristics

Pinus strobus is easily grown in average, medium, and well-drained soils.  It prefers full sun, fertile soils, and cool climates.  It is tolerant of a wide range of soil conditions, but intolerant of many air pollutants such as sulfur dioxide.

Additionally, the White Pine is the “Tree of Peace” of the Haudenosaunee Confederacy.  The tree has its roots in the creation of the League of Five Nations, but its cultural significance continues even to today.

image of White Pine at St. WilliamsGarden Uses

Pinus strobus is cultivated by plant nurseries as an ornamental tree, ideal for planting in gardens and parks.  The species are low-maintenance and grow quickly into a specimen tree.

Smaller specimens are popular as live Christmas trees.  Eastern White Pines are noted for holding their needles well, even long after being harvested.  They are also well suited for people with allergies, as they give little to no aroma.

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Our species of the month for December is the White Pine (Pinus strobus) and just in time for the holidays! Here are the Fast Facts!

Hardiness Zone:
50-80 feet; 15-24 metres
20-40 feet; 6-12 metres
Full Sun
Rabbit, deer

This beautiful tree looks great this time of year, and really gives off a Christmas-y vibe! Look out for our Species Profile later this month.

Don’t forget to follow us on Facebook and Twitter for more Fast Facts, and shots of our beautiful species.


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Panicled Aster (Symphiotrichum lanceolatum) in the understory; Burlington

Restoration biologists aim to return ecological function to degraded landscapes, by using plants to recreate healthy ecosystems. Landscapes that have been actively disturbed are restored by planting trees, meadows, wetlands and gardens. There is increasing interest to reshape the spaces we have disturbed into healthy and productive ecosystems, with a focus on the use of regionally appropriate native species.

Though we have gone to great lengths to shape the land, plants are the original ecosystem engineers.

Image of: dense blazing star liatris spicata

Dense Blazing Star (Liatris spicata)

Plants are the foundation of every terrestrial ecosystem on earth. Their primary function is to provide animals with food, and materials to make shelter, but they also clean the air, and provide us all with oxygen. Plants also cool us with shade, and buffer us from floods.

Similarly, native plants are the foundation of regional ecosystems they are native to. Though often overlooked as the green backdrop upon which life’s drama unfolds, the specific identity of the plant communities that surround us is important.

Natives are species which occur in a region naturally. They have evolved over generations to exploit resources and cope with challenges found within their home region. Because they have evolved in the same ecosystem, native animals often prefer and sometimes depend exclusively on native plants.

Restoring native plants is a critical first step for conserving ecosystems. Avoiding the use of nonnative plants, especially well documented invasives, in our landscapes will also help to prevent further ecological damage.

The greatest threat to native plant diversity is loss of habitat from development, and the associated spread of exotic plants species. Some of the most invasive plant species in Ontario were introduced with the best of intentions to provide forage for our domestic animals, and to make our neighborhoods more beautiful. The cost of these invasions is more than space; we are paying for these mistakes with the loss of distinct and diverse communities of native plants and their associated fauna. Restoring native species to our landscapes increases the quality of forage and habitat for wildlife, but it also helps us plan for and mitigate the effects of climate change.

Image of: Gray headed coneflower Ratibia Pinnata

Gray Headed Coneflower (Ratibia Pinnata)

Since native plants are adapted to the local environment, they can tolerate regional variations in moisture and temperature better than many traditional, introduced, cultivars. While also being more attractive and rewarding to insects, native wildflowers, for example, are more drought tolerant and cold hardy than their cultivar counterparts, or non-native analogues.

We can use this to our advantage, and plan landscapes of native plants that require fewer inputs, and in the end lower costs to create and manage. There are even native plants adapted to harsh environments that mirror our disturbed urban and suburban environments, such as roadsides and other infrastructure corridors, rooftops, construction footprints, and old fields — native plants that thrive on river bluffs, alvars, sand dunes and fire-prone prairies.

Though they are hardy, wild populations of native plants are increasingly fragmented by development. This makes migration extremely difficult for many plant species in Ontario. Without the ability to migrate, these plants may not be able to cope with a changing climate, and without reconnecting populations through assisted migration, they may fail to adapt to the change. Land stewards who are interested in restoring native plant ecosystems can help by enhancing native plant population sizes and creating gene flow between populations by establishing new patches.

Whether you appreciate nature in the water, casting off the side of your canoe, or you appreciate it in the air, through the lens of your binoculars, conservation begins in the ground with the seeds and roots of native plants.

Article courtesy Stefan Weber, Ecologist – St. Williams Nursery & Ecology Centre

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Article Provided by: Ariana Burgener, St. Williams team member.

Fall has finally arrived and with shorter days and chillier temperatures come the beautiful autumn colours. Now is a wonderful time of year to see the yellows, oranges, and vibrant reds that we at St. Williams Nursery & Ecology Centre look forward to each year. Among our many favourites for displaying bold fall colours is the Freeman’s Maple (Acer x freemanii).

Noteworthy Characteristics

Freeman Maple is a naturally occurring hybrid of Silver Maple (Acer saccharinum) and Red Maple (Acer rubrum) found throughout Southern Ontario. It has the stunning red autumn foliage of the Red Maple, and the fast growth of a Silver Maple. As a hybrid, it is hardier and easier to grow and it can tolerate poor site conditions better than a Red Maple would. Although the Acer x freemanii is often found naturally in wetland and swampy forests, it also does well planted in dry sites and tolerates urban settings well.

Garden Usesimage of freeman's maple

If you’re looking to add some fall colour to your yard, the Freeman’s Maple is an excellent choice. It’s a gorgeous shade tree and grows to be about 50 to 80 feet tall, growing to an oval shape – taller than it is wide. The root system is often shallow and does not exhibit aggressive growth, so it’s less likely to harm pipes or other city infrastructure.

For the best Fall impact, plant Freeman’s Maple next to shrubs with yellow fall foliage. Some excellent native species include Witch Hazel (Hamamelis virginiana) and Spice Bush (Lindera benzoin). This will give your yard a beautiful array of contrasting colour.

Why Do Leaves Turn Different Colours?

During fall, the days are shorter and the temperatures are cooler. This triggers plants to start shutting down for winter. As part of this process trees and leafy shrubs stop producing chlorophyll – the green pigmented molecule that absorbs light needed for photosynthesis. Once the tree stops producing chlorophyll, the cold weather helps to break down what remains. As the green pigment fades, other pigments in the leaves are revealed. Carotene – the yellow pigment found in carrots – is always present in leaves, but isn’t visible until chlorophyll has faded.

In addition to stopping production of chlorophyll, certain conditions within certain species can prompt the production of anthocyanin – the red pigment found in apple skins and grapes. The purpose of anthocyanin is somewhat debated, whether it is to help protect the now yellow leaf from sun damage, to help the tree retrieve as much sugar and nutrients from the leaves as possible, both, or something else entirely. Either way, the conditions for bright red leaves include cold but not freezing temperatures, bright sunny days, dry weather, and nutrient poor soil. These conditions increase the production of the red pigment, resulting in bright red foliage.

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Prepared by SWNEC Ecologist, Stefan Weber

Whether summer arrives early or leaves late,   selecting drought tolerant plants for our gardens is increasingly important. Approaching garden design with an aim to reduce and eliminate the need for irrigation is called xeriscaping. Ontario’s native species are some of the best choices. Not only are they well adapted to our hot summers and cold winters, they are the best at supporting native wildlife as well, especially goldenrods and asters.

When designing your garden, make sure not to over-mulch the soil. This can actually prevent moisture from reaching the roots. A thin layer of fine shredded or straw mulch is best, no more than 3-4cm. A living mulch, or green mulch of low growing perennial plants is even better at shading the soil and keeping moisture in the ground.

Tallgrass Prairie species like Culvers Root and Ironweed have deep roots and can definitely take the heat, but also grow very large, and can by too messy, floppy or unruly for a small garden, an urban garden, or a public space.  The best plants are some of our most uncommon and unusual and are found in savannahs, alvars, and sand barren habitats.

The Best Drought Tolerant Native Plants for Sun

Prairie Smoke (Geum triflorum): Deep pink flowers in spring give way to a smoky cloud of seed pods in summer. G. triflorum spreads slowly, but stays very short. This alvar species thrives in a rock garden and  looks great in a mixed border.

Field Pussy Toes (Antennaria neglecta): full sun and poor soil is no match for this little ground-cover. Producing silver and yellow flower heads in spring, followed by a flush of new leaves turning silver and then evergreen.

Whorled Milkweed (Asclepias verticillata):  Does your garden resemble Sahara in the summer? Do you want to attract butterflies? This is the milkweed for you! Whorled milkweed is the smallest and most drought tolerant of our milkweed species. It also also the longest boom period, and is easy to divide once mature. Creamy-peach flowers sprout almost all summer amongst dark grassy foliage.

Dwarf Blazing Star (Liatris cylindracea): A pollinator magnet, with fuchsia flowers in the mid to late summer. Unlike other blazing star species,  Dwarf Blazing Star has low sprawling stems, punctuated with fuzzy flower heads.

Hairy Beardtongue (Penstemon hirsutus): Another alvar species, Hairy, or Pink Beardtongue blooms in late spring and early summer. Foxglove-like flowers are held above the low growing foliage on slender spikes. Bumble-bee approved!

Frosted & Slender Vervain (Verbena stricta,  V. simplex): These species grow in thin soils in full to part sun. Slender Vervain is very short, and produces lilac coloured flowers in early summer. Frosted Vervain on the other has much brighter pink flowers, but can grow to almost one metre.

Honorable Mentions: Nodding Onion, , Upland White Aster, Wild Strawberry, Grey Goldenrod, Smooth Aster


The Best Drought Tolerant Native Plants for Shade:

Pale Leaved Sunflower (Helianthus strumosus): With lemon yellow blooms in late summer that attract butterflies, this sunflower only grows up toe 1m, but will spread widely in well-drained soil. Loves dry, shady sand.

Silver-rod, (Solidago bicolor): One of the prettiest native Goldentod species, the Silver-rod has a mix of creamy yellow and pure white florists that wrap around a longer, slender stem. It thrives in part shade on well drained soil

Large Leaved Aster & Heart Leaved Aster (Eurybia macrophyla, Symphiotrichum cordifolium): Though similar in appearance, these two different species of woodland aster bloom in early fall. Flowers range from white to bluish to pinkish. The Large Leaved Aster spreads like a groundcover, keeping its big leaves close to the ground, and forming an airy, float-topped inflorescence. The Heart Leaved Aster stays in a dense, bushy clump and flowers later in the season.

Honorable Mentions: Wild Columbine, Wild Ginger, Yellow Pimpernel, Hepatica


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Noteworthy Characteristics

The Whorled Milkweed, also known as Asclepias verticillata, is a small, clump forming species that is as resilient as it is beautiful. The plant blooms to be a beautifully natural greenish-white and will grow to be about half a metre tall. Milkweeds tend to thrive in disturbed areas in poor soil (which can include sand and gravel) and the Whorled Milkweed is no exception. What’s unique to the Whorled Milkweed though, is that it flowers on very slender indeterminate stems. Because of the way the plant flowers, it continues to bloom later in the season.

Garden Uses

Asclepias verticillata prefers full sun, moderately moist to dry conditions, and soil containing loam, clay-loam, sand, or gravel. Asclepias verticillata actually does best in infertile soil as it reduces competition from taller plants. It can spread quite aggressively in open sunny areas with exposed soil.

Interesting Facts

  • The Nectar produced by Whorled Milkweed is a food source for many insects. The plant is a great pollinator, and will aid you in doing your part in protecting the bee population.
  • Because of the look of the slender stems on which the plant flowers, Whorled Milkweed has earned the nickname “Horsetail Milkweed”

Asclepias verticillata is in bloom right now, and looks absolutely magnificent. Giving bees a safe rest stop something that you can feel good about, and because the plant acts as a larval host for Monarch butterflies, your garden may start to look a touch more magical once it’s planted. So get your order of Asclepias verticillata in today!

To inquire about availability please call 1 866 640 8733 or email

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