Invasive Plants

One of the challenges with this project has been determining which plants are welcome in our yard and which are not. The term "weed" is often used to describe those plants that people decide are not welcome in their gardens. Our research on native plants has uncovered a wide variety of facts and opinions. Non-native plants (also called non-indigenous plants, invasive plants, alien plants, exotic species, or weeds) are plants that have been introduced into an environment in which they did not evolve. Introduction of non-native plants into our landscape has been both accidental and deliberate.   The whole thing gets more confusing when you recognize that a plant, which is native to your area, is also aggressive. This often gets it labeled as a weed because it shows up in ornamental flower gardens and among crops.

For the purposes of this project, we have decided that all plants native to Illinois are welcome. It is hoped, that as long as we do not interfere too much, natural checks will keep things in balance. In the case of shrubs and trees we are being somewhat selective. Our yard is not large and we do not wish for it to become a young forest at this time. The trees are doing their best to convince us otherwise as they dump huge amounts of seeds every year.  We pluck most of the seedlings which pop up around the yard.

This page will feature some of the invasive plants we have encountered and how we have dealt with them in terms of the project goals. Additional pictures are available in a gallery format grouped by the first letter of the genus.

  • Non-Native:Plant species living outside their native distributional range due to human activity, either deliberate or accidental. These are weeds in Native Suburbia and we pull them all.


Common Illinois lawn grasses:

Kentucky bluegrass (Poa pratensis)
Fineleaf sheep fescu (Festuca filiformis Pourret)
Hard fescue (Festuca trachyphylla)
Perennial ryegrass (Lolium perenne L.)

Other common names: grass, turf, yard, golf course, median, park, athletic field

Lawn grasses are the most insidious of invasive plants, simply because of the fact that most people not only allow them to grow, but they also go to extraordinary lengths to keep them alive.

Americans are in love with lawn. It is the most widely used groundcover in parks, school grounds and public open spaces.  While some lawn areas are used for recreational activities, many parks and open spaces contain vast lawns that are rarely used for any type of recreation, provide few benefits to the public and are costly to maintain.

The modern lawn requires significant amounts of water to thrive. In urban areas, lawn irrigation uses as much as 30 percent of the water consumption on the East Coast and up to 60 percent on the West Coast. The deep root systems of many native plants increase the soil's capacity to store water. Native plants can significantly reduce water runoff and, consequently, flooding.

Natural landscapes do not require mowing. Lawns, however, must be mowed regularly. Gas powered garden tools emit 5 percent of the nation's air pollution. Forty million lawnmowers consume 200 million gallons of gasoline a year. One gas-powered lawnmower emits 11 times the air pollution of a new car for each hour of operation.

Vast amounts of fertilizers are applied to lawns. Excess phosphorus and nitrogen – the main components of fertilizers – run off into lakes and rivers causing excess algae growth. This depletes oxygen in our waters, harms aquatic life and interferes with recreational uses.

Although many people associate wild areas with allergies, the average lawn is just as guilty.  Kentucky bluegrass (Poa pratensis) accounts for most of the hayfever in the eastern U.S. during May and June.

Although Americans love lawn, many parks have large lawns that are rarely used for recreational purposes. A much better use of most of these unused lawns would be to plant them with native plants, mimicking the local native ecosystems. These native plantings will provide unique education and recreational opportunities, reduce maintenance costs, solve management problems, and give residents a better sense of the region where they live. Compared to lawns, native plantings provide users with a higher quality of life for a lower cost.

The pictures above are a look at the lawn that existed in Native Suburbia before we took steps to rectify that mistake.

Bitter Nightshade (Solanum dulcamara L.)

Other common names: Bittersweet, dulcamara, nightshade, climbing nightshade, woody nightshade, deadly nightshade, amara dulcis, fevertwig, violet-bloom, blue bindweed, felonwort, poisonberry, poisonflower, pushion-berry, morel, snakeberry, wolfgrape, scarlet berry, tether-devil, dwale, skawcoo.

A perennial, somewhat woody vine with small star-shaped purple flowers and green berries that turn red when ripe. Bitter nightshade spreads by seed, but its stem, which is about 2 to 8 feet long, can also root as it creeps along the ground.  The leaves are from 2 to 4 inches long, some having one to three lobes at the base.  Bitter nightshade is sometimes called deadly nightshade, but that name implies a greater threat than the plant actually poses. It is mildly poisonous, but the toxic substance, solanine, is most concentrated in the unripe berries.  Just do not eat any of this plant and you will be safe.  Check out the USDA Natural Resources Conservation Service for more details.

In our yard we found that the nightshade had sprung up along the fence and entwined itself among other bushes and plants.  We did not realize how much there was until we identified it and began to eliminate it.  Not wanting to use herbicides, we opted for hand pulling along with a little digging for stubborn roots.  The soil where it was growing was fairly moist, so the roots came out relatively easy.  I am sure we missed some bits, but we are keeping our eyes out for new sprouts.  We put the unwanted plants on our compost pile.  Hopefully that will be the end of it, but we will watch the area for escapees.  The nightshade in our area generally has leaves with the two distinctive lobes, which makes it easy to identify.  We also noticed that insects must like it because it is common to observe plants with many small holes in the leaves.  The pictures above were taken in a local nature preserve.  We had already pulled everything in our yard before deciding to post this.

Garlic Mustard (Alliaria petiolata [Bieb] Cavara & Grande)

Garlic mustard is a cool season biennial herb with stalked, triangular to heart-shaped, coarsely toothed leaves that give off an odor of garlic when crushed. First-year plants appear as a rosette of green leaves close to the ground. Rosettes remain green through the winter and develop into mature flowering plants the following spring. Flowering plants of garlic mustard reach from 2 to 3-1/2 feet in height and produce buttonlike clusters of small white flowers, each with four petals in the shape of a cross.Once introduced to an area, garlic mustard outcompetes native plants by aggressively monopolizing light, moisture, nutrients, soil and space.  Check out the USDA Natural Resources Conservation Service for more details.

Due to our ignorance, the first appearance of garlic mustard in our yard was met with enthusiasm.  The first year plants have cute heart-shaped green leaves.  We were pleased to see something sprout in the first Spring after killing off the grass.  These hardy pioneers began growing in two shady areas among some ornamental gravel.  The gravel was around before we started Native Suburbia and we had consolidated it in two different corners to get it out of the way.  In a short time a fairly large area was covered in a fluffy green carpet.  Then came the fateful day when we identified garlic mustard as an aggressive alien invader.  The gravel made it difficult to get all the roots, but a shovel made short work of the problem.  I am sure we will be doing battle with this plant in the future, but now we know how to identify it.   In the end the cute green plants were added to the compost pile.  The elimination of the garlic mustard occurred before we thought to take pictures.  Those seen above were taken in a local nature preserve.

Glossy Buckthorn (Rhamnus frangula)

Common Buckthorn (Rhamnus cathartica)

Both glossy buckthorn and common buckthorn are woody shrubs or small trees that can reach up to 20 feet in height. These non-native trees were introduced from Europe and Asia.  Glossy buckthorn has gray-brown bark and lightly colored lenticels which give the bark a speckled appearance. Leaves of glossy buckthorn are 1-3 inches long and shiny on the upper surface, oval shaped and slightly wavy. Flowers are 5-petaled, greenishwhite and the fruits are red, turning almost black when ripe.

We have about 20 glossy buckthorns in our yard.  This extremely aggressive tree looks innocent enough along our fence. The birds seem to love the copious amounts of berries that they produce. The fun begins as the seeds are spread all over the yard and hundreds of little buckthorns sprout up everywhere. The specimens that are well established along the fence are being allowed to stay for now. Their eviction would be a large project that we do not wish to tackle at this time. We do keep an eye out for the fast growing seedlings and pull them before they can establish themselves.  In the future the source of the seedlings will be eliminated as well.

[Update: October 2005]
The buckthorns are gone!  I bought an electric chainsaw and chopped them down over the course of two weekends.  Unfortunately they were too bulky to go on the compost pile in our little yard so we put them out to be chipped and taken away.  We still have to deal with the stumps.  There are sure to be many sprouts from them in the spring as the buckthorns continue to fight.  We will be ready to chop and pull them until the war is over.  If you are thinking that Roundup would help prevent the emergence of new sprouts, you are probably right.  But we do not believe in the use of herbicides when alternatives are available.  We should be able to manage this task without poisoning the ground.