Keystone Plant Species of Illinois

Are you ready to make a difference and support our ecosystem? One easy way to start is by adding a few keystone species to your property. Keystone species are native plants that have the most significant positive impact on the ecosystem.

Oak Trees

Oak trees (latin name Quercus) are the host plant for 456 species of caterpillars! This makes them the number one plant in our region for its benefit to our ecosystem. With 20 varieties of oak that are native to Illinois, it is easy to find one that will fit your taste and your space. 

Some of the most common Illinois oak varieties include: 

  • White oak 
  • Swamp white oak 
  • Red oak 
  • Bur Oak 
  • Chestnut Oak 
  • Chinkapin Oak 
  • Pin Oak 

Oak trees have a reputation for getting very large. While this can be true, there are varieties that stay more contained. The swamp white oak gets 50-60 feet tall and wide and does well as a shade tree on any landscape. If you would like one that is much smaller try the dwarf chinkapin oak. The dwarf chinkapin grows to only 15-20 feet tall and wide! 

Oak trees also have a reputation for being very slow growing. However, the pin oak and northern red oak are actually considered fast growing trees! The beautiful white oak is considered to have a moderate growth rate. 

If you are going to be planting a shade tree on your property, please consider an oak. There is no better plant for our local environment than an oak tree. 

Plum/Cherry Trees

The latin name for plum is Prunus. Plum species native to our area include:

  • Prunus americanus: 15ft-25ft, understory tree, sun or part shade, dry to medium conditions
  • Prunus nigra: 15ft small tree, sun or part shade, moist well drained
  • Prunus hortulana: 20ft thicket forming tree, sun or part shade, moist well drained
  • Prunus susquehanae (Sesquehana sandcherry): 2ft to 6ft shrub, full sun, moist well drained

Native plums are great for birds and used by 345 species of moths and butterflies as host plants. The beautiful white blooms in the spring make them an important source of food for early season pollinators.

If you are looking to plant a small tree or shrub, please consider one of our native plums. Planting this keystone species will help our local ecosystem.


Goldenrod (Solidago) packs a big punch when it comes to ecosystem benefits. It alone is host plant to 112 species of butterflies and moths in our area! It is certainly one of the more important native plants in our region.


Goldenrod is sometimes falsely accused of being responsible for seasonal allergies or hayfever. However, this is not the case.  Ragweed is the culprit.

There are four varieties of goldenrod native to our area.


  • Early goldenrod (solidago juncea) grows up to 3 feet tall in sun to shade, dry to moist soil.
  • Giant goldenrod (solidago gigantea), also known as early goldenrod and smooth goldenrod, will grow 2 to 6 feet tall. It prefers full to part sun with moist to wet well drained soil.
  • Missouri goldenrod (solidago missouriensis var) is a low growing goldenrod that only reaches 1 to 2 feet tall. It prefers full sun and dry soil.
  • Zigzag goldenrod (solidago flexicaulis) grows to 3 feet tall in part sun to shade. It tolerates most soil conditions. Zigzag is a vigorous variety and is best used in larger gardens.

Joe-Pye Weed

Joe-Pye Weed (Eutrochium purpureum, Eutrochium maculatum, also referred to as eupatorium) is a very unfortunate name for this incredible native plant. It certainly is not a weed and it can be one of the most beautiful flowers in the garden.


Joe-Pye has masses of lightly scented lavender flowers that are literally a magnet to butterflies and other pollinators. It is not particular to soil type and will grow well in full sun to part shade in medium to wet soil. Its great service to pollinators and the fact that it is a host plant to dozens of butterfly and moth species are what make this a must have keystone plant. The icing on the cake is that it is very deer resistant… And did I mention beautiful?


There is really not a negative thing about Joe-Pye Weed. One concern for small gardens may be its size. Joe-Pye can grow up to seven feet tall. While this would be lovely in many areas, it may be too large for some. But while it is usually best to stick with pure natives, this is one plant where we may want to consider a cultivar. “Little Joe” (eutrochium dubium) and “Baby Joe” (eupatorium hyssopifolium) are great cultivars that reach only four feet, which makes them suitable for any location. These smaller substitutes provide the same effect while needing less room. This is such a beneficial plant for our ecosystem, every garden needs a few!

Birch Trees

Birch  (Betula) trees and shrubs can be quite attractive. They have nice foliage and often a soft, almost weeping branching effect. Most have interesting white or peeling bark that creates winter interest. They host 274 species of butterflies and moths. Their seeds are loved by birds. Where you find birches, you will find American goldfinch. A few species are native to our area.

  • Bog Birch (Betula pumila). This shrub birch grows to 9 ft tall. It prefers wet soil in sun or shade. If you have a wet corner of your yard this may be just the shrub for you.
  • Gray Birch (Betula populifolia). This fast growing, relatively short-lived tree grows to 30 ft tall. It prefers moist to medium soil in full sun and is especially happy in sandy soil. It is usually multitrunked and has very attractive white bark.
  • Paper Birch (Betula papyrifera). Paper birch is one of our most beautiful native trees. It grows 50 to 75 ft tall It can be single or multi trunked and has very attractive white peeling bark.  Paper birch grows in sun to shade and prefers moist cool soil.
  • River Birch (Betula nigra). River birch is a lovely tree that grows to 50 ft tall (possibly taller in some locations). It has extremely attractive peeling bark and a graceful growth habit. River birch prefers part sun to part shade with moist to wet soil. It is fast growing and long lived. This is the healthiest, most disease resistant birch variety.

A beautiful birch might be just the plant for you if you have moist to wet areas on your property.



Wild Strawberry

If you are looking for a groundcover that is native and can make a big impact on your local ecosystem, look no further than wild strawberry (Fragaria). Cultivated strawberries are hybrids of this sweet tasting native. They sport attractive white flowers in the spring, sweet berries in late spring/early summer, and red foliage in the fall. They grow in full sun to mostly shade, dry to moist soil. You can’t get much more adaptable than that! Best of all, wild strawberries host 64 species of caterpillars in our area!

This groundcover with multi-season interest will help prevent weeds in your garden. Use this in your planting beds instead of fabric or thick mulch. This will make your landscape more hospitable to caterpillars and ground nesting bees.

There are two varieties that are native to our area:

  • Virginia strawberry (Fragaria virginiana)
  • Woodland strawberry (Fragaria vesca).

Plant some wild strawberries this spring. The birds, bees, and caterpillars will thank you!



Midwest native willows (Salix) are host plants for 299 species of native butterflies and moths. Host plants provide the food for developing caterpillars. Willows are also the earliest blooming native trees and shrubs. They provide critical pollen and nectar for early emerging spring bees.

What often comes to mind when we think of willows is the large weeping willow that we see along streams. We think that is too large and messy for our property.  Weeping willows are actually not one of our native willows. They are native to China. Many varieties of willow native to the Midwest are much smaller and more appropriate for suburban landscapes. Below are some examples of these.

  • Bayberry Willow (Salix myricoides). This large shrub grows 6 to 12 ft tall in full sun with moist to wet soil.
  • Bebb Willow (Salix bebbiana). This small tree grows 12 to 25 ft tall in full sun to shade with moist to wet soil.
  • Bog Willow (Salix pedicellaris). This small shrub grows 1 to 5 ft tall in full sun with moist to wet soil.
  • Prairie Willow (Salix humilis). This small shrub grows 4 to 5 ft tall in sun/part sun with medium to dry soil.
  • Pussy Willow (Salix discolor). This very attractive large shrub or small tree grow 10 to 20 ft tall in full to part sun with moist soil.

As you can see, there is a willow variety for every area. If you would like to plant a very beneficial shrub or small tree on your property, please consider a native willow.





There are so many benefits of sunflowers (Helianthus) that no garden should be without some. They come in a variety of different sizes and colors, are no fuss, and tolerate a wide range of soil and growing conditions. Here are a few of the garden benefits of sunflowers.

  • Pollinators, pollinators, pollinators!  Sunflowers attract butterflies and bees galore. In fact, there are a number of specialist bees that will only use the pollen of sunflowers.
  • Sunflower pollen protects bees from pathogens that are partially responsible for pollinator decline.
  • The seeds from sunflowers are a favorite of birds. The high fat content of sunflower seeds helps birds keep warm during colder months.
  • Sunflowers detoxify your garden soil. They absorb toxic heavy metals and leave your soil healthier.
  • Sunflowers inhibit the growth of weeds. There are compounds in all parts of sunflowers that inhibit the growth of some other plants. For this reason, plant a grouping by themselves rather than mixed in with other plants.
  • Last but certainly not least, sunflowers are the host plant for 77 species of butterflies and moths! This makes them a powerhouse plant for supporting our ecosystem and food chain

Sunflowers native to our area:

  • Ashy sunflower(Helianthus mollis) grows 1-3 feet tall in full sun
  • Fewleaf sunflower(Helianthus occidentalis) grows 3 feet tall in full sun
  • Giant sunflower(Helianthus giganteus) can grow up to 15 feet tall in full sun
  • Hairy sunflower(Helianthus hirsutus) grows 3 to 5 feet in full-part sun
  • Maximilian sunflower(Helianthus maximiliani) grows 3 to 10 feet tall in full sun
  • Paleleaf woodland sunflower(Helianthus strumosus) grows up to 7 feet tall in sun, part shade or shade
  • Prairie sunflower(Helianthus petiolaris) grows 1 to 4 feet tall in full sun
  • Sawtooth sunflower(Helianthus grosseserratus) grows 3 to 12 feet tall in full sun
  • Stiff sunflower(Helianthus pauciflorus) grows 3 to 6 feet tall in full sun
  • Thinleaf sunflower(Helianthus decapetalus) grows 4 feet in part shade, moist conditions
  • Willowleaf sunflower(Helianthus salicifolius) grows 4 feet tall in full sun
  • Woodland sunflower(Helianthus divaricatus) grows 3 to 6 feet tall in full to part sun

There is a sunflower variety for every location and space. Plant a few this year and help our pollinators!

Maple Tree

Keystone plant species have the greatest beneficial effect on ecosystems. The final keystone plant for our area that we will highlight is The Marvelous Maple Tree. We will soon have all of the keystone plants that we’ve highlighted in this series featured on our website.


There are a few varieties of maple that are native to the Chicago region. Two of them, the silver maple and the sugar maple, are not usually desired on residential lots. They are more suited for very large lots or open natural areas due to their aggressive roots and large size. However, one native species of maple is more suited to urban and suburban yards; the red maple (Acer rubrum). Its roots are less aggressive and it grows in a conical to round shape, 40-60 feet tall. The red maple’s beautiful fall color makes it a landscape favorite and one of the most commonly planted trees.


Red maple grows best in full to part sun. It is very adaptable to different soil conditions; from dry to wet it will do well as long as drainage is good. Maple spring flowers are a great source of nourishment for spring pollinators. They are also the host plant for at least 255 species of butterflies and moths. If you would like a fast growing, beautiful shade tree, you should definitely consider a red maple.


Leadplant (Amorpha canescens) is a powerhouse keystone plant in our area. Although not as well- known as many of our other keystone species, this small shrub has high ecosystem value. It is a pollinator magnet and host plant to 35 species of caterpillars.


Leadplant has attractive purple spike flowers and blooms best in full sun with medium to dry soil. Growing 1 to 2 ft tall, this plant is extremely drought tolerant once established. There is no need to fertilize as, like all plants in the legume family, it pulls nitrogen up from the soil.


Leadplant is one of the few true shrubs of the prairie, and it is part of the historic fabric of our area.                                           

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