Insects occupy several trophic levels in the myriad of food chains that can exist within woods and forested areas. Native trees can support hundreds of different species of insects because they absorb more of the sun's energy through greater internal reflection and because they have coevolved with their insect symbionts over long periods of time. Trees support insects by providing pollinators with nectar and pollen, by providing massive amounts of food for phytophagous insects, and by providing crevices where insects can hide. By using trees to provide food for these animals, one actually supports a diverse range of animals including mammals and birds that eat insects. It is rare for a tree to be noticeably damaged by herbivorous insects and even rarer to be killed by them unless they are being attacked by exotic insects such as gypsy moths or Asian longhorned beetles. Therefore, native trees require less pesticide applications. If you have the space and the inclination, then plant a native tree to increase diversity in your garden.
The following list (with a few extra trees noted for their ability to please pollinators*) is taken from Tallamy (2007). It is arranged according to the number of species of butterflies and moths associated with each tree. To avoid disappointment, be careful to choose a tree that is going to do well in your local conditions. You can spend lots of money buying a tree; you can buy a small bare root; or you can try growing it yourself from seed. This latter option is often much easier than you might think.
| Name |
Notes |
Quercus sp. (Oaks) |
These trees support a huge range of species both in N.E America and other parts of the northern hemisphere. In North America, many oaks are successional species that wait hundreds of years as a seedling for a gap in the canopy before springing upwards. These trees host up to eight different species of butterfly in Southern Ontario. |
| Salix sp. (Willows) |
Willows are moisture loving plants. If you see these plants away from water in Toronto, then they are usually in hollows or areas that have previously been drained. Their seeds are spread by waterways and spring melts and their roots can survive oxygen deprivation due to flooding. A larger number of butterflies feed on this hostplant than any other type of tree and the male plants support spring pollinators. |
| Prunus sp. (Cherries and plums) |
Most species of Prunus available from nurseries are not native. However, there are some such as chokecherry that are easy to grow. They support spring pollinators. Also, they are
hosts to red-spotted purples, eastern tiger swallowtails, hairstreaks and sphinx moths. |
| Betula (Birches) |
Birches are host plants for several butterflies and large moths. They also support many birds. Whatever the conditions are in your garden, there is probably a native Birch that will grow well. |
| Populus (Cottonwoods) |
The most impressive member is the Eastern Cottonwood. These trees are typically found in flood areas close to the water table. They are host plants for several butterflies as well as being an important source of food for birds. |
| Crabapple (Malus) |
Crabapples flower early in the season and are important plants for pollinators at this time. |
| Vaccinium (Blueberries) |
Host plants for several butterflies including Brown Elfins, Striped Hairstreak and Spring Azures. They support spring pollinators that can buzz pollinate. |
| Acer (Box elder) |
The female tree is better for insects and birds alike, but you have to put up with lots more weeding. I leave the seeds on the ground to be eaten by box elder bugs. The seeds of box elder are a winter food source. |
| Ulmus (Elm) |
This is not a tree I would plant, due to its susceptibility to Dutch Elm disease. However, if you already have one growing it is worth keeping. |
| Pinus (Pine) |
The White Pine, the provincial tree of Ontario, is an outstanding tree for wildlife. It supports over 250 species of insects as well as a range of other wildlife. Other pines probably also support a wide range of wildlife. |
| Carya (Hickory) |
Provides food for nearly 200 species of insects. It is also a preferred food for some small mammals. |
Crataegus (Hawthorne) |
Hawthorne flowers profusely in the spring. Their flowers produce lots of nectar; the leaves and haws support many insect species including several butterflies. |
Amelanchier * (Serviceberry) |
An excellent plant for spring pollinators, which is an added bonus considering that it is also great for birds too. |
Tilia americana* (Basswood) |
A nectar producing tree for spring pollinators. The nectar is quite concentrated and these trees produce copious amounts. |
| Aesculus glabra |
Flowers in May and is a popular nectar source for queen bumblebees. |
| Cercis canadensis |
Flowers in April and therefore serves spring pollinators. |
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Aronia melanocarpa is a great source of nectar to insects active in springtime. |
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| Aronia melanocarpa |
This shrub flowers in May. It supports a range of insects and is swamped by bees when in flower. |
| Cephalanthus occidentalis |
A shrub for mid-summer pollinators in wetter areas |
| Cornus sp.* (Dogwoods) |
Most Dogwoods are actually shrubs. Many of them flower in mid-spring and are tremendously important for a large number of different bees. |
| Physocarpus opulifolius * (Ninebark) |
This large shrub is overloaded with flowers in the spring that are enjoyed by a number of bees and flies. |
