Questions on: Creeping Jenny

Ron Smith, Horticulturist, NDSU Extension Service

Q: I have had creeping Jenny in my garden for two years. We sprayed with Roundup three times in 2005. We sprayed before planting and while the garden was growing. It took over the garden that year, so the only thing we were able to harvest was a few potatoes. We did not plant a garden last year and did not spray (as I gave up on it), but the creeping Jenny didn't seem as bad. I would like to have my garden again this year, but I'm afraid the creeping Jenny will take over again. What can we do this spring to get this weed under control? (e-mail reference)

A: Field bindweed (creeping Jenny) is very difficult to control because of its extensive root system. In turf situations, where cultivation is not practical, a postemergent herbicide is recommended. Small infestations of bindweed in nonturf areas sometimes may be controlled by covering the area with mulch and not allowing any green plant material to emerge. Field bindweed control is best achieved when plants are actively growing and in the seedling to flower stage of growth. Multiple applications may be required for complete eradication. The reason for it not appearing to be as bad last year is probably linked to your persistence the previous year, which weakened the energy reserves of the plant's root system. I really think your best approach is to follow a combination approach of spraying anything that comes up with Roundup and covering the area with a black tarp for this growing season to hopefully starve the plant to death!

Q: I have creeping Jenny in my azala, rose and hydranga beds. It seems to suffocate the roses. Do I need to worry about it suffocating any other plants? (e-mail reference)

A: Creeping Jenny has one of the most extensive root systems on Earth and will smother everything near it. Id do something to get it out of your landscape beds if they are of value to you, even if it means hiring a landscape maintenance company to come in and do the work.

Q: What can I do to get rid of creeping jenny in my yard? Is there a spray that will not kill the grass? Also, I want to plant a couple Aspen trees. What time of year should I plant them? (Bowman, N.D.)

A: Trimec will kill creeping jenny with a couple of applications about six weeks apart. You will probably get some re-growth next spring, but with another application, it should be under control. Aspen, or any trees for that matter, can be planted anytime they are containerized. In fact, if a local nursery has the trees growing in containers, now would be the best time to plant because the soil is warm, there is no or very little top-growth taking place and the roots will get off to a good start for the next season.

Q: We are having a problem with creeping Jenny. Do you know of a spray that we can use that will not harm our lilac hedge or any other flowers? (Lehr, N.D.)

A: There is nothing that you can spray to kill this weed that will not also harm the ornamental plantings if any drift occurs. Careful application of Trimec, just to wet the foliage, not soak it, and protecting the desirable plants from drift spray should do the job with repeat applications. This perennial weed, like all other such weeds, are most effectively controlled when herbicide applications are made in the late summer or early fall.

Q: Will Preen help control creeping jenny in my yard and flower beds? (Glenfield, N.D., e-mail)

A: I wish Preen would control creeping jenny. Unfortunately, that simply is not the case, and we are forced to pull out the heavy artillery to bring it under control—a Trimec product to control just the weed or Roundup to wipe out everything. Or, you can learn to live with the creeping jenny where it is the dominant plant in your yard. It makes an excellent groundcover where turfgrass will not grow. The decision is yours!

Q: I have some dahlia bulbs that I started in pots to give them a head start, and when they were an inch high I brought them upstairs to give them some light. I was planning to put them outside for short periods of time to harden them up, but before I had a chance the weather turned windy, then rainy. Now they are 2 to 3 inches high. Can I still harden them or can they be trimmed? I also would like to know if I can safely use Preen around my rose bushes and hydrangeas to get rid of the creeping jenny or dharlie that is in them? (Glenfield, N.D., e-mail)

A: Yes, you can still harden them off and even prune them back if you wish. The wind will be the biggest enemy of these (and most plants in North Dakota!), so you may want to stake them or find a protected spot for them in the landscape—if such a place exists.

Yes, Preen can be used safely around roses. Creeping jenny is a tough weed to bring under control. If you have a pure stand of it, use Roundup to kill it off. It may take repeat applications to get rid of it. Where it is mixed with grass, you may have to use a formulation known as Trimec to bring it under control. Fall—between mid-August and mid-September—is the best time to control this and other broadleaf perennial weeds.

Q: Can you tell me how to get rid of creeping jenny? It is running rampant in my yard, and I was thinking of waiting until fall to treat it with a herbicide, but I'm not sure. (Pierre, S.D.)

A: I certainly would not wait until fall to apply herbicide control, because I guarantee the creeping jenny will flower before then.

Declare war on this deep-rooted weed as soon as active growth is noted in the spring. You will need to use a combination of mechanical controls (hoeing) and chemical. For the mechanical it requires doggedly taking out the new growth from the roots every 14 to 18 days; treatments in your fallow areas with chemicals like Roundup are most effective during peak flowering periods. In the lawn, repeat applications of Confront or Trimec will be needed.

If this weed has been established for a while like it sounds, expect to invest two growing seasons in getting it under control.

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