We all love it when our plants thrive—until they start taking over other spaces and spreading aggressively! While many of our garden plants need to helped along, some take hold and start branching out on their own. Aggressively spreading plants can be a wonderful source of groundcover, but they can also cause problems for their neighbors. Let’s dig in and take a look at aggressively spreading plants, learn about some species that are prone to spreading aggressively, and what we can do to help keep them contained.
A quick note before we begin: Many sources we consulted referred to these as “invasive species”. In fact not all of them are. An invasive species is better defined as a non-native or alien species that has been introduced from elsewhere and starts crowding out native species. An invasive species may be an animal, plant, insect, or microbe. For more information and a list of invasive species in North America, visit this portion of the USDA’s website.
Common Garden Plants That Spread Aggressively
Spreading plants may spread in a variety of ways depending on species. Some produce rhizomes—stem structures that grow below the ground—which allow the plant to spread beneath the surface. Some produce a similar structure called a stolon, which is a portion of the stem that grows along the surface and puts down roots periodically with each root site becoming a new plant. Others just put out lots of seeds and let that take care of it.
Common rhizomatous spreaders include the following plants:
- Lilyof the Valley (Convallaria majalis)
- Spurges (Pachysandra spp)
- Creeping phlox (Phlox stoloniferia)
- Yarrow (Achillea millefolium)
- Bamboos (Phyllostachys sppand others)
- Comfrey (Symphytum officianlis)
- Japanese Knotweed (Reynoutria japonica)
Popular garden plant which are stoloniferous include:
- Mints, of all kinds (Mentha spp)
- Raspberries and Blackberries (Rubus spp)
- Self-Heal (Prunella grandiflora and Prunella vulgaris)
- Deadnettles/Lamiums (Lamium spp)
- Chinese Lantern (Physalis alkekengi)
And finally common garden plants that are aggressive reseeders:
- Angelicas (Angelica archangelica and Angelica gigas in particular)
- Sweet Annie (Artemisia annua)
- Borage (Borago officinalis)
- Sea Oats (Chasmanthium latifolium)
- Purple Coneflower/Echinacea (Echinacea pupurea)
- Fennels (Foeniculum vulgare)
- Mallows (Lavatera spp)
- Silphium spp
- Verbana spp
There are many, many more in each of these categories, so it’s important to do a bit of research as to what plants may spread aggressively in your area. Different climate, soil, and regional conditions can lead to different species becoming aggressive spreaders, so forewarned is forearmed!
Containing Aggressively Spreading Plants
So, how do you contain plants that are prone to spreading aggressively? As your grandmother may have told you “an ounce of prevention is worth a pound of cure”. Before installing spreading plants in your garden, think about how you’ll contain them and stop the spread. The best and most reliable way to do this is to put these plants in containers, preferably on a man-made surface like a patio, deck, or other hardscape. This will prevent rhizomes and stolons from spreading and help contain the spread of seeds. Edging materials can help if the rhizomatous and stoloniferous plants are already in the ground, but these may be less effective.
Tilling and weeding do not help with rhizomatous and stoloniferous plants in the long run. Unless done very carefully by hand and including soil-sifting to separate out broken pieces of stolon or rhizome, the broken pieces will actually help spread the plant further. If such plants are already established in a space, aggressive mowing/weed eating can help limit future spread. Some folks cover an affected area with a tarp on the ground (held in place with bricks or stones) until the spreading plant dies off. It’s a long process and requires constant maintenance, no matter what control techniques you employ.
If you’re dealing with aggressively spreading plants in your yard or garden, we hope this blog helps you find the solutions you need. If you’ve grown and managed them successfully, we’d love to hear from you about what worked and what didn’t so please get in touch!
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