Invasive plants - Ask Extension
Your website has been so helpful to me, so thanks in advance :)
We moved into a new house a few months ago which have some beautiful professionally-l...
Knowledgebase
Invasive plants #638490
Asked May 20, 2020, 3:14 PM EDT
Your website has been so helpful to me, so thanks in advance :)
We moved into a new house a few months ago which have some beautiful professionally-landscaped beds in addition to some questionable choices. We've cut down a ton of Amur honeysuckle that was pruned and cultivated, and we are up to our eyeballs pulling out english ivy (both are a still a back breaking work-in-progress).
1 - I think we have some chameleon plants that I've read are invasive in some regions but were not categorized as so in your list. Should I pull them out?
2- In one of those lanscaped beds, we have some Heavenly Bamboo. Some neighbors identified it for me and told me about its toxicity so I've removed all of last season's berries and pulled out the babies it spawned. I don't see it on your list either and also some neighbors said they have it too, and love it. For the toxicity alone, I'm thinking of cutting them down and plastic sheeting them to solarize.
The roots are growing into my irises but they are also in a contained bed (but only contained 6 inches deep). Please advise if you agree with cutting them down and when I should do that.
Also in lieu of glyphosates for all the plants mentioned above, would solarizing work and is it possible to wait until winter? I hate that it looks so ugly but I'm willing to do it sooner than later if needed. Also am I killing native species in the process?! What's the right thing to do.
Lastly, once this is all cleared, I would love to plant a butterfly/pollinator garden though some of the area is shaded- do you have resources to support that?
And a very big thank you from Kensington!
Montgomery County Maryland
Expert Response
Chameleon Plant (Houttuynia cordata) is invasive and should be removed. It may not be problematic enough for state regulation here, though it is known to be invasive in several other states. Interestingly, it does not appear in records on the Maryland Biodiversity Project's page, which documents species occurring in natural areas in the state. Repeated applications of non-selective herbicide, like glyphosate, would be needed if (repeated) physical removal is not working. Addition of a spreader-sticker (also called an adjuvant or surfactant) product may help get the herbicide to stick to its somewhat waxy leaves. Follow the directions on the label on these products, and keep the spray away from desirable plants. Unfortunately, removal of Chameleon Plant can be a drawn-out battle.
Heavenly Bamboo (Nandina domestica) has been a recent addition to the state's invasive species list, where nurseries are permitted to sell it but only with clear cautionary warnings. It has been recorded in a few locations: https://www.marylandbiodiversity.com/view/16068. Berries are unsafe for birds and mammals to eat in large quantities, though they rarely do. It would be safe to remove them as well, though their presence will not endanger the safety of any nearby plantings. They can be cut down and pulled/dug up at any time.
Soil solarization is not intended to kill perennial plant roots as much as it is soil-borne pathogens (like nematodes) and weed seeds. It can be effective to about 8 to 12" deep, but shrub roots can run deeper than this. It is also designed to be used over unshaded ground during a two- to three-month stretch in the height of summer, when temperatures will reach their highest point beneath the plastic. Winter solarizing, especially for the purpose, would likely not be helpful.
The most immediate and practical control of the Nandina would be removal. Cut it repeatedly or dig up its root ball and monitor for suckers (root sprouts). Each time they any visible growth is removed, the root system loses energy. Eventually, the plant(s) will become exhaused and die out.
Butterfly / pollinator gardens are relatively easy to plan in that a wide array of plants are suitable. Sunny gardens may have more candidates than shady ones, but there are still lots of choices. Narrowing-down options by the plant's habitat preference (sunlight levels, soil moisture), deer palatability (if applicable), desired mature size, and flowering season will help. Using a diverse group of plants, with varying bloom times and flower styles will attract the widest possible array of pollinators.
You can start your research with some of the recommendations on these pages, though they are by no means exhaustive. Most of these publications have lists on the final pages for plants most appropriate for use in various growing conditions (dry shade, moist sun, etc).
https://marylandgrows.umd.edu/2018/04/25/plant-for-pollinators-9-ways-to-attract-and-help-pollinators-in-your-garden-and-yard/
https://drive.google.com/file/d/0B25LXUJQvd_6YlBhd1ByTzY2ZW8/edit?pli=1
https://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG120_Native_Plants%20_of_MD.pdf
https://www.fws.gov/chesapeakebay/pdf/NativePlantsforWildlifeHabitatandConservationLandscaping.pdf
As a starting point, popular native flowering perennials and shrubs for use in afternoon shade for attracting pollinators include:
Miri
Heavenly Bamboo (Nandina domestica) has been a recent addition to the state's invasive species list, where nurseries are permitted to sell it but only with clear cautionary warnings. It has been recorded in a few locations: https://www.marylandbiodiversity.com/view/16068. Berries are unsafe for birds and mammals to eat in large quantities, though they rarely do. It would be safe to remove them as well, though their presence will not endanger the safety of any nearby plantings. They can be cut down and pulled/dug up at any time.
Soil solarization is not intended to kill perennial plant roots as much as it is soil-borne pathogens (like nematodes) and weed seeds. It can be effective to about 8 to 12" deep, but shrub roots can run deeper than this. It is also designed to be used over unshaded ground during a two- to three-month stretch in the height of summer, when temperatures will reach their highest point beneath the plastic. Winter solarizing, especially for the purpose, would likely not be helpful.
The most immediate and practical control of the Nandina would be removal. Cut it repeatedly or dig up its root ball and monitor for suckers (root sprouts). Each time they any visible growth is removed, the root system loses energy. Eventually, the plant(s) will become exhaused and die out.
Butterfly / pollinator gardens are relatively easy to plan in that a wide array of plants are suitable. Sunny gardens may have more candidates than shady ones, but there are still lots of choices. Narrowing-down options by the plant's habitat preference (sunlight levels, soil moisture), deer palatability (if applicable), desired mature size, and flowering season will help. Using a diverse group of plants, with varying bloom times and flower styles will attract the widest possible array of pollinators.
You can start your research with some of the recommendations on these pages, though they are by no means exhaustive. Most of these publications have lists on the final pages for plants most appropriate for use in various growing conditions (dry shade, moist sun, etc).
https://marylandgrows.umd.edu/2018/04/25/plant-for-pollinators-9-ways-to-attract-and-help-pollinators-in-your-garden-and-yard/
https://drive.google.com/file/d/0B25LXUJQvd_6YlBhd1ByTzY2ZW8/edit?pli=1
https://extension.umd.edu/sites/extension.umd.edu/files/_images/programs/hgic/Publications/HG120_Native_Plants%20_of_MD.pdf
https://www.fws.gov/chesapeakebay/pdf/NativePlantsforWildlifeHabitatandConservationLandscaping.pdf
As a starting point, popular native flowering perennials and shrubs for use in afternoon shade for attracting pollinators include:
- Lobelia (Lobelia cardinalis and Lobelia siphilitica)
- Woodland Sunflower (Helianthus divaricatus)
- Turtlehead (Chelone)
- Blue Mistflower (Eupatorium coelestinum, a.k.a. Conoclinium)
- Summersweet (Clethra alnifolia)
- Violets (Viola)
- Phlox (Phlox divaricata and Phlox stolonifera)
- Eastern Columbine (Aquilegia canadensis)
- Golden Ragwort (Senecio aureus)
- Pinxterbloom and Swamp Azalea (Rhododendron periclymenoides and Rhododendron viscusum)
- White Wood Aster (Aster divaricatus, a.k.a. Eurybia divaricata) and Blue Wood Aster (Aster cordifolius, a.k.a. Symphyotrichum cordifolium)
Miri
