Morning Glories are Fine; Bindweed is Not!
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Q. Mike: I've been thinking about adorning part of my fence with annual morning glories this summer, but have heard that this fragrant, fast growing climber has the potential to become a perennial problem as it self sows and can 'take over' the garden. Should I think twice about this? If I am willing to 'take a chance', must I be adamant about preventing each flower from going to seed? Or is the 'self sowing' overrated in our USDA Zone 6? Thanks,
- ---Loyal Listener Alison in Villanova, PA
- ---Jan in Highwood, IL
The vines are not self-supporting, so they are typically grown over a fence, or (famously in some Chicago neighborhoods) up string running from the ground to the roof of a building. The individual flowers are ephemeral; they open a rich blue in the morning, become purple in the heat of the day and then crumple and die that same evening. But there can be a lot of them, and every flower gives birth to a seedpod that will drop its distinctive dark, little rock-like seeds onto the ground for next season.
So yes, Jan—you can prevent them in future seasons. If you apply a corn gluten meal product that's labeled for use as a pre-emergent herbicide to the soil early in Spring, those seeds should be inhibited from sprouting. If you miss that 'prevention' window, the young vines are easily hoed or pulled out of wet soil. Mulch fence lines and other non-planted areas heavily with wood chips, or sheets of newspaper or cardboard covered with soil. Flame-weed any young sprouts that appear at the outskirts or spray them with a high-strength vinegar or herbicidal soap.*
It really isn't that hard; and if you prevent seeds from dropping over the summer, you will get zero volunteer vines the following year. (As I learned the season I collected every seedpod from my morning glories for an organic seed house.)
Q. Morning Glories have taken over a raised flowerbed in my backyard. Every year I have to constantly pull them out. We have even sifted the dirt thru a screen. I would appreciate any suggestions you might have on getting rid of them. Thanks,
- ---Donna in Bensalem PA
- ---Karen in Whitinsville, Massachusetts
- ---Andrea in Seattle, Washington.
Just think about this plant's common name: 'Bind' is the prefix. 'Weed' is the suffix. And there ain't no 'fix' in between, boys and girls. But hey, get started in the spring and you got the whole summer to spruce up that house! A new range in the kitchen, a little paint here and there and you're good to put that 'for sale' sign out in October! (Right after you mow everything to the ground, including the trees….)
There are two kinds of bindweed.
Although hedge bindweed (Convolvulus sepium) spreads by seed and by creeping rhizomes under the ground, it can be eliminated; you just have to pull, torch, vinegar, or soap every new shoot. 'Rubbing' won't do it and would get old fast. Use a high-strength vinegar or professionally made herbicidal soap to really coat the weed. Spray (or flame weed) the flowers and leaves at high noon on hot, dry, sunny days*; with a helper using big pieces of cardboard to shield your wanted plants. If possible, remove any wanted plants and cover the entire area with heavy cardboard covered by lots of dirt or wood chips for the season.
Field bindweed (Convolvulus arvensis) is one of the toughest of all weeds. Its roots go down to China. (Yes, Mandarins ARE pulling the blanched root hairs of your plants out of their soil right now.) The only real cure is to mow the area tight to the soil and then solarize it (see This PREVIOUS QUESTION OF THE WEEK for details) or do the weighted cardboard thing for the entire season, being vigilant to torch, soap, pull or vinegar any shoots that try to escape on the outskirts.*
For prevention, pull new vines as soon as they appear—and keep your soil as dry as possible. Bindweed thrives in moist, rich earth, and dry dirt is it's only real enemy. So don't water that raspberry patch; dry soil will weaken the weed, but won't bother the berries one bit.
*(See This PREVIOUS QUESTION OF THE WEEK for lots more details on using soap, flame and vinegar against tough weeds.)