In the garden, there are good guys and there are bad guys. Most often we think of bad guys as weeds, diseases and insects. These are truly bad guys. But there are other bad guys. Bad guys that find their way into your heart, acting as a wolf in sheep’s clothing. They are hiding right in plain sight — on garden center shelves and in mail-order catalogs.
I often complain about some common invasive plants that people grow on purpose. I was happy to sit in on a lecture last weekend at the West Virginia Master Gardener Conference by naturalist Emily Grafton, who discussed common garden plants that are or can become invasive. I think it is high time that gardeners and garden retailers realize the real damage that some of these plants can do when they escape your yard.
What makes a plant invasive?
There are a few qualities that make a plant invasive. First, it has a long growing period that helps it outcompete other plants. It either comes up early and bullies other plants, or hangs on late so nothing else can get a start. An invasive also spreads easily, either through vegetative propagation from roots or from seed. They are also adaptable to a wide set of soil and environmental conditions, especially poor conditions like heavy soils.
A plant’s invasiveness can vary by location. A plant that is not invasive elsewhere can be invasive here at home, so pay attention when buying plants from national companies or at garden stores in other parts of the country. (I usually buy a plant on travels when I can — I’m not above putting a plant in my suitcase, much to TSA agents’ confusion or dismay.) Be sure to do some research when choosing new plants you have little experience with.
Some of these plants only become an issue if they are not controlled by humans. So, is there an issue if you plan on keeping them under control? While you may plan to keep them under control now, what happens if you don’t have time to keep everything controlled? Or if you get sick? Or if you move away and the next homeowner doesn’t know that the plant can be invasive? You could be causing future problems without planning to do so.
Roundup of bad plants
Sure, some of these plants look innocent enough, but if left uncontrolled they can cause issues. Here’s my invasive garden enemies list. Don’t get mad if one of your favorite plants is on it.
Enemy No. 1: English Ivy
I’m sorry to say, but English ivy (Hedera helix) is a very invasive plant. It can spread through woodlands if left untended and can smother out trees. I’ve seen many stands of ivy that are destroying native plants. Last year, I got several calls from concerned homeowners that their ivy had been killed back by the winter cold. Many did not appreciate that I said they should be happy about the dead ivy.
Other enemy vines
English ivy isn’t the only villainous vine. Periwinkle (Vinca minor), Oriental bittersweet (Celastrus orbiculatus), Chinese wisteria (Wisteria sinensis) and Japanese honeysuckle (Lonicera japonica) are all invasive plants that can bully out others.
Enemy No. 2: Purple loosestrife (the purple menace)
You can find this pretty purple enemy on many a garden center shelf. Gardeners plant purple loosestrife (Lythrum salicaria and L. virgatum) for its beautiful blooms and love of wet areas (it is commonly planted around ponds and streams). Its love of water is the big problem, however. This plant is becoming a menace in wetlands, killing out native plants and destroying habitat for wildlife.
Enemy No. 3: Japanese barberry
This barberry (Berberis thunbergii) is a common foundation landscape plant. It is popular to plant under windows, as its thorns help deter potential burglars and its red color is attractive. However, it escapes your yard when birds eat the berries and spread the seeds. It can grow thick in forests and crowd out the understory.
Other shady shrubs
Burning bush (Euonymus alatus) is a popular landscape shrub that is a horrible invasive that spreads to the woods and open lands. Chinese privet (Ligustrum sinense), autumn olive (Eleagnus umbellata), Japanese spirea (Spirea japonica) and bush and tartian honeysuckle (Lonicera maackii and L. tartarica) are also common invasives for our region. You may be surprised to know that butterfly bush (Buddleia davidii) is also invasive in the area. While you may be doing a good thing by feeding pollinators, you could be creating problems with this attractive shrub.
Enemy No. 4: Miscanthus, the ghastly grass
There are a few of the ornamental grasses that spread around the area and displace native vegetation around the country. Japanese silvergrass, more commonly called by its Latin species name Miscanthus sinensis, is a common invasive plant in our area. I’ve seen big stands of some of these grasses growing wild as I’ve driven down the road.
Enemy No. 5: Empress tree takes over
Several garden catalogs will sell you an amazing tree that grows 20 feet a year and produces beautiful purple flowers. This tree (Paulownia tomentosa) goes by a few aliases. Sometimes they call the tree empress tree and sometimes the princess tree. It doesn’t tell you that in our area it produces thousands of seeds that can spread. This tree grows in transition areas at the edge of the forest and roots out many of the native species. I’ve seen this tree out west and been alarmed, only to be told that it isn’t invasive there (just in the Southeast). Sure, it’s pretty, but it is becoming enough of a problem that gardeners should take note.
Other troublesome trees
The empress isn’t the only problem. Norway maples (Acer plantanoides), white mulberries (Morus alba) and white poplars (Populus alba) can all be invasive problems if they escape your yard.
What to do about invasives
First off, you should do research and adopt a policy of avoiding invasives in your garden. I know that there are some plants on this list you probably enjoy, but avoiding them can really cut down on problems spreading in our region.
Next, be sure to inform your fellow gardeners about these plants’ invasive nature, and don’t be afraid to notify managers or owners of local nurseries, garden centers and stores that are selling them that they are invasive. Sometimes they don’t even know.