Frequently Asked Questions


Where can I obtain a copy of the school yard naturalization manual that you published?

Both the first edition, published in 1994, and a second edition, published in 1996, are sold out. There are no plans to publish it again, but there are some principles that all schools need to consider: Try to make your project last as long as possible, so that students in incoming years play a part in the evolution of the garden. The project should include examples of ecosystem conservation, expansion and linkage so that students have in mind the characteristics of what is needed to repair the larger landscape beyond the schoolyard. Some local libraries may have copies to lend.

School yard and community projects can make use of the resources at the Evergreen Foundation. Schools in particular should consider the environmental curriculum framework designed by the Toronto District Schoolboard that focuses attention on sense of place, ecosystem thinking and human impact.

How do I attract cardinals to my backyard?

cardinal on branch

The Northern Cardinal is likely the "most wanted" bird by home owners. But, while it comes to many backyards, some people never seem to see them. Cardinals are often nervous about going into the open, so if your yard is quite open, try planting shrubs and small trees. Not only will they provide perches and cover in the winter, they provide fruit and nesting sites in the summer months. Try species such as dogwoods, ninebark and nannyberry. Conifers such as white spruce and cedar provide very good winter cover. Because it may take a while for your shrubs and trees to get big enough, a quick solution is to collect your neighbours old Christmas trees - really! You may have people give you some odd looks as you drag their curbside post-holiday tree down the street to your home, but these leftovers provide great habitat for wintering birds. I've done this many times and the birds used them a lot. I suggest collecting 3 dense, tinsel-free (birds might get tangled) trees and lean them against each other in an upright position. Most species of conifers will keep their needles for a long time if kept outside and this makes them nice to look at as well as bird-friendly. In the spring, I just put them at the back of the property as a brush pile.

I am interested in planting native trees on my property, where can I find trees for sale?

plant sale

If you live in Wellington County, try contacting The Green Legacy program. This fantastic project of the County of Wellington aims to plant over 150,000 native trees each year!

It is also important to consider areas that need not be planted, eg. where natural forest migration is already underway. For sites that are removed from natural forest migration and for shelterbelt establishment, native trees are best and climate adapted seed sources are an important consideration. The Forest Gene Conservation Association of Ontario FGCA  is a good resource for understanding seed source and the Society of Ecological Restoration  for resources on what to plant. The two organizations combine resources to put a Native Plant Resource Guide together every two years. It can be obtained by calling 1-800-667-1940. The resource guide lists most of the independent native plant nurseries in Ontario .

The Arboretum Auxiliary holds a plant sale on the second Saturday of September, 9:00 a.m. to 2:00 p.m., at which many native Ontario species are available.

I found this bug in my house - what is it?

rove beetle

Obviously there are a lot of different insects and so you might think that answering this question is impossible. But, 90% of these questions have to do with certain species that infest warm houses in the fall. Species like Leaf-footed Bugs, Box Elder Bugs and Ladybird Beetles (Lady Bugs) seem to dominate the house scene in late September and October. Click here to see a Leaf-footed Bug, click here to see a Box Elder Bug and click here to see a Multicoloured Asian Ladybird Beetle. These species overwinter as adults and your house seems to be a good spot to do this. Our Indoor Wildlife ID sheet can help you identify many of the insects (and other critters!) around your house. 

I have a black walnut tree and want to know how long the toxin stays in the ground if I cut the tree and what will grow under it if I leave the tree?

The chemical in question, juglone, is mostly produced in the roots (which spread a distance equal to the height of most trees) and works as a germination inhibitor. Combined with shade, the juglone can make vegetable gardening quite difficult without imported soil in raised beds and without full sun. There are many native plants that will grow under black walnut and you can create what I call an Aviary with many fruit producing plants such as red elderberry, raspberries, bittersweet, virginia creeper, pawpaw, nanyberry and woodland plants such as baneberry, jack in the pulpit and false Solomon's seal.

I have a huge elm tree that is starting to show signs of Dutch Elm Disease, what can I do to save it?


The Arboretum is the home of Ontario's Elm Recovery Project which is designed to capture the Dutch Elm Disease tolerant genes in Ontario for breeding purposes. We are interested in the characteristics and location of all Ontario elms that are greater than 213 cm, or 7 feet in circumference. 

All elms get Dutch elm disease infections and certain individuals have a strong enough immune system to fight it off. All trees die at some point in time however, due to age, drought or other stresses that compromise the immune system enough that Dutch Elm Disease finally takes over. Treatment is possible (and costly) but is not a long term cure. You can contact an Arborist through to do the treatment work.

I have a maple tree with black spots on the leaves. What is it and will it kill my tree?

The black spots are a fungus disease called Tar Spot. It infects Norway maple (including all of the horticultural forms such as "Crimson King"), Silver maple and Freeman's maple. The disease infects leaves late in the season and has little impact on the overall health of the tree. The disease is already widespread and sanitation (leaf removal) is not effective in reducing the infestation level for the following year, so let the leaves decay under the trees to at least improve the soil health. Norway maples are generally short lived along city streets, but the seeds move through storm sewers into natural areas where, once they germinate and grow, they are able to shade out native plants. Consider planting a replacement for your Norway maple.

Norway maple often gets powdery mildew (a white surface on the leaves) at the same time of year and it is also considered harmless to the tree.

I have a tree (shrub) that seems to have a pest or disease.

Insects are part of the ecology of plants and most plants can easily tolerate an infestation of insects. Occasionally, a new pest outbreak will seem overwhelming but natural predators tend to show up and ultimately reduce the "pest" to a minor occurrence. Such was the case for Gypsy moth and Viburnum Leaf beetle.

Diseases tend to not be able to kill a plant unless the plant is weakened (compromised) by other stresses such as drought, improper soil match or incorrect light level.

Pest and plant questions are readily handled by the University of Guelph's Lab Services. This is a fee-for-service organization but they are equipped with current information on pests and diseases and choices in control - including "do nothing" if nothing needs be done.

I have dead trees in my woodlot and need advice on how to manage it?

mushroom growing on a dead log

Woodlands should have some dead wood in them if they are to remain healthy. Dead standing wood and coarse woody debris on the ground provide important habitat for animals that keep the forest healthy. It is helpful to have your woodlot interpreted by a professional, contact the Ontario Woodlot Owners Association (OWA) at 613-258-0110, Toll Free 1-888-791-1103, for valuable assistance.

If you suspect a serious pest like Asian long-horned beetle to be present (usually where shipping crates from China have been stored) The Canadian Food Inspection Agency (CFIA) takes the lead in managing imported organisms. The Federation of Ontario Naturalists supports the intention to eradicate this invading insect.

I want to grow acorns from a fine oak tree nearby and have tried for years, what do I have to do?
  1.  Acorns: In nature, squirrels gather acorns to eat and some will be buried or cached for later. If the squirrel forgets where it buried all of the acorns, some acorns may grow into trees that could live for up to 300 years. Perhaps the squirrel is instinctively planting some trees for future generations of squirrels. The acorns of white oak were eaten by early peoples as a food staple. Perhaps native peoples also planted acorns in centuries past. During heavy crop years, acorns can be found on the ground from mid-September to early October. During light crop years, the squirrels will consume the crop by mid-September. You can pick some up for growing at home or plant some at the edge of the woods but first break a few open to look inside. They should be bright white throughout. Also, look for the tiny embryo at the pointed end. Sometimes weevils (an insect) eat the insides of the acorns and produce a partly or entirely brown, powdery interior. Acorns that are still on the tree when others are on the ground tend to be weevil-free seeds. Healthy seeds will sink after soaking for 12 hours in water while dead, weeviled seeds tend to float. Do not let acorns dry out for more than a week.
  2. Growing Oak Trees: Most oaks produce seed only on alternate years. Pick acorns from low branches or from the ground in September when they are starting to change colour from green to reddish-brown and some of them are starting to drop. Locate a lightly shaded part of the garden and plant healthy seeds within a few days of gathering them. Plant them on their side at a depth of twice the thickness of the seed (a guide for virtually all seeds). Make a fully screened, 30 cm high enclosure with half inch mesh chicken wire so that the mice, squirrels, chipmunks, and human feet can't get to them (ensure that the mice and chipmunks can't dig under the enclosure by burying a 2x4 frame that the screened enclosure fits on). After the acorn germinates, it is still very tasty so leave the enclosure over the seedlings for the entire first growing season. Oak seeds germinate in May. They will grow to about 15 cm high the first season. After two to three years the trees will be large enough (30 to 50 cm) to plant in a permanent place. A few seeds can be planted right where you want a tree to grow, just make sure the animals can't get at them. Oak seedlings have a deep root and must be dug with care to keep at least 30 cm length of root intact.
  3. Planting an Oak: Different oak species are particular as to soil and drainage. Ideally, the oak that you choose occurs naturally in your area. Record the soil and drainage characteristics where you gathered the seeds to help you determine the right conditions to plant the new trees into. You might also take note of the other kinds of plants that grow with the oak.

Natural soil is organized in layers, with the rich humus at the surface. Remove the turf from the planting site and shake the soil from the roots. Excavate a hole by layers, keeping the layers in separate piles. Set the sapling into the hole and replace the soil so that the layers go back in the same order. Soak the soil when you are finished. Mulch the planting site with wood chips or oak leaves (humus is at the surface of the soil). Keep a tree guard around the trunk, for a few years, so that rabbits, groundhogs and mice will be less likely to eat it. Keep in mind that these animals have a role in maintaining meadows as a site for much of the food web. Try not to fill all meadows full of trees.

Remember that not every seed or tree will survive - that is nature's way. By planting more seeds than are necessary, establishment can be assured and still allow you to give some young oaks away. If you wish to learn more about growing native plants from seeds, The Arboretum offers a comprehensive, full day workshop every September. Visit our Workshops page for more information about upcoming workshops, pricing and how to register. 

I would like some help in determining what to plant in my yard.

Garden Flowers

Questions of this nature are beyond a phone call consultation and it depends on the scale and nature of your project as to where you could go for further help. The most important consideration is the soil moisture and aspect. If your site is dry and hot you need to consider the use of xerophytic plants that love those conditions and you will not have to water such a landscape. Visit the Gosling Wildlife Gardens at The Arboretum for ideas on wildlife friendly gardening.

Fill your garden with plants that you like. Visit The Arboretum at least once a season and take note of the plants that stand out for you. They are labeled and that allows you to read about the ones that draw your attention. If the site you have will support the plant you are interested in, then search out a nursery/garden centre or plant sale that offers that species or variety.

School yard and community projects can make use of the resources at the Evergreen Foundation. Schools in particular should consider the environmental curriculum framework designed by the Toronto District Schoolboard that focuses attention on sense of place, ecosystem thinking and human impact.

General plant and gardening questions can often be answered by the Ontario Master Gardeners (Guelph and Wellington County Master Gardeners can be reached at 519-824-4120 ext. 56714 or For planting on properties adjacent to natural areas, we recommend that you consider using native plants only, to reduce the possibility of adding exotic species to the area. Consulting ecologists can be located through the Society for Ecological Restoration (SER).

My cat is constantly killing birds. How can I stop it from doing this?


Unfortunately, there isn't an easy solution to this one. Bells on collars are not a complete solution because often by the time they ring it's too late for the bird. Behaviour modification isn't going to work because you can't be there every time the cat hunts. Doing anything when your cat appears with its prey will only stress the cat out - it is too late for it to associate its hunting instinct with your displeasure. The only real way to stop the hunting is to keep your cat indoors or have an outdoor enclosure for your cat. Depending on the cat, this may be easy, or seemingly impossible. The Cats and Birds: Keep Cats Safe and Save Bird Lives has some suggestions that might help.

If it is a neighbour's cat that keeps catching your backyard feeder birds, chipmunks and cottontail rabbits, try to situate your feeder so it is in an open area not too close to shrubs or things the cat can hide behind. If this is impossible, you can put a short wire fence barrier between the cat's pouncing spot and the feeder. This will slow the cat down as it will have to go around or over the barrier to get to the birds, giving the birds a little extra time to escape.

My tree is dying and I have been told that you can help save it?

tree leaves

Trees do die and there is little that can be done to reverse the process once it is noticed. By the time most people notice a tree dying, there is little to do but plant new trees nearby. Nature plants new trees all the time and when an old tree dies, there are young ones already filling the gap. In our landscapes, we tend to assume that our statuesque, isolated trees will live forever. Consider locations to start new trees near or even under large trees before they even start to decline and prune low branches to accommodate the new tree as it grows.

Arboretum staff do not do site visits or diagnosis over the phone. Tree care and maintenance inquiries are directed to the Yellow Pages under Tree Service to locate a certified arborist. We recommend a second opinion on serious tree problems and arborists serving your area can also be contacted through the International Society of Arboriculture Ontario which also provides information and other resources.