Knowledgebase
Does a product like RoundUp kill underground spring bulbs ??? #744707
Asked April 16, 2021, 4:22 PM EDT
I have a fairly large perennial bed that includes a LOT of spring bulbs. It also has been invaded by a number of ground covers including Creeping Jenny, Snow on the Mountain, and (worst of all) THE CHAMELEON PLANT (Houttuynia cordata). I have read a number of articles that say that the only way to get rid of this last plant is to remove all the desirable plants from the area then blast it with RoundUp or similar product. I guess I can pull up the roses, mums, bee balm, peonies, and whatever else is in there and then drown the area in roundup, but I am wondering if this will kill the spring bulbs too? (there are hundreds of daffodils and tulips currently in bloom). Or, do you have another idea on getting rid of those ground covers? I particularly hate the chameleon because it actually stinks. I can wait till the foliage on the daffys and tulips dies back if necessary.
Thank you for your time.
Livingston County Michigan
Expert Response
Hello Patricia
Yes, if glyphosate is applied to spring bulb foliage, it can kill the bulbs. The best time to kill weeds with herbicide is the fall, when their sap is traveling down to the roots. The second best time is during or after flowering, when plants are typically weak from expending energy to produce flowers.
The weeds you list are difficult to control and will need repeated applications of herbicide, and repeated digging out of roots and sprouts. Instead of spraying, you may paint the herbicide onto the growing leaves of the weeds, shielding and avoiding the nearby perennials A foam brush or a cloth glove wetted with herbicide worn over a water proof glove ( yes Really All Waterproof please to protect your skin) can be used to get herbicide on the weeds.
The way glyphosate works is the plant must be actively growing and air temperature should be 60F or above. The herbicide must be applied to leaves, and some is absorbed through stems, too. From the leaves it moves into the roots. It can take a few days to 2 weeks to kill the plant- until then the plant should be left in place.
As always, please read and follow all precautions on any chemical you use.
Look for a product with the highest percentage of active ingredient you can find, such as a “brush killer” type product. Read and follow the directions on the label.
Here are some details on how glyphosate works: https://www.canr.msu.edu/news/killing_weeds_in_the_garden_with_glyphosate
