Knowledgebase
getting rid of ground elder #752322
Asked May 26, 2021, 3:10 PM EDT
Hello. We have a large flower bed that has been taken over by ground elder. We took a lot of it out last year, stems, leaves and roots, but it has come back. My husband wants to start digging up all of the flowers (lilies, irises, forget me nots, peonies) and keep them in pots while we work on removing the ground elder. This may take a few months. I have a few questions about this process.
1. Is this the best way to deal with ground elder?
2. Will digging flowers up before they bloom this year harm them? Will they flower this year if we dig them up now? Will they come back next year? How long would they be OK in pots?
3. We also have 3 very old, large rhododendrons in the same flower bed. How can we best kill the ground elder around them? Do we need to try to dig them up?
4. Is it possible to actually get all of the ground elder out?
Any other advice you have about dealing with ground elder is appreciated.
Thank you,
Lesley Mughazy
Kalamazoo County Michigan
Expert Response
Hello Lesley,
You can keep your perennial flowers in pots, but they may not flower. Digging does stress the plants. If you need to keep them over winter in pots, the pots will need to be sunk into the soil and mulched. You can do this right from the start, if desired.
I wouldn’t try removing large shrubs. Instead, consider using a herbicide around them, and place a cardboard shield over the shrub’s trunk, leaves and branches, then paint on the herbicide or spray carefully on a day when the wind is still and the air is fairly cool - 75 degrees or lower. The shield can be removed once the herbicide is dried and the temperature is cool. (Hot temps can cause a freshly applied herbicide to volatilize and travel on the breeze)
Note that herbicides are most effective on young leaves, and that repeated applications will be necessary. You can mow the plant to the soil line, allow new young leaves to sprout, and treat them with glyphosate. You must either shield other garden plants or lift them out of the soil temporarily, so as not to kill them with herbicide, too. When using a non-selective herbicide glyphosate, spray it on, leave the plants for 3 weeks so the pesticide can move to the roots, then remove the dead plants. It is likely that you will need to reapply.
Glyphosate does not move through the soil, so nearby roots of shrubs will be safe.
Another treatment is to mow it down and immediately and completely cover the area with black plastic, sealing the edges down on the soil so no light enters. You will need to leave the plastic in place for at least a year. Check the edges of the plastic and kill any sprouts. Hand pulling is also an option, but will need repeating over several seasons, as the roots starve by being deprived the leaves. Any of these options still mean you need to monitor the area for the next few years and immediately control any sprouts.
When working amongst these plants it is suggested to wear gloves and protect your skin. The sap within members of the Carrot family, such as goutweed, can cause blistering upon exposure to UV light from the sun if skin is exposed. It is the same substance found on the exterior (and interior) of giant hogweed. People are not as likely to encounter it on other Carrot members as it is on the inside and the goutweed plants would need to be broken open to expose the sap.
Glad to help. Be persistent with this one!
