Both have beautiful petunia-like flowers. Both are aggressive vines. Both are in the sweet potato family. Both are a menace in crop fields, and both invade non-crop areas.
Field bindweed (Convolvulus arvensis) is perennial and morning glory (Ipomoea purpurea and other species) is annual. Field bindweed always has white flowers and morning glory can be found in many colors. Field bindweed is always considered a noxious weed, while morning glory is often planted in flower gardens.
Annual morning glories are a very close relative to the commercial sweet potato. They are both in the genus Ipomoea. Morning glories produce large quantities of seed. Sweet potatoes rarely do.
Keeping morning glory seed from dissipating usually solves the weed problem. However, these aggressive but beautiful vines usually don’t play nice. They will cover anything that doesn’t move. Fortunately, once a good frost hits a plant, it’s gone. Sometimes simply lower night temperatures and higher humidity is enough for foliar diseases to set in and do the trick.
Bindweed is another story. It’s a perennial with an aggressive root and rhizome system. This weed can reduce crop yields by more than half. It’s not easily chemically eradicated either. Many herbicides that will kill it will also harm crop plants. Problems are the same in flower gardens.
In broadleaf crops like soybeans, cotton, potatoes and sweet potatoes control is especially challenging. If crops are harvested with some potential growing season left, control is more promising. Treatment with a broadleaved systemic herbicide or a non-selective systemic like glyphosate can begin to destroy the underground parts of the plant.
Control is a little easier in grasses like wheat and corn. Broadleaf herbicides won’t hurt these crops and eventually bindweed can be controlled. Killing plants before they go to seed is important too. A single plant can produce over 500 seeds and each one can potentially remain dormant for decades.
Vines with white funnel shaped flowers and leaves shaped like arrowheads must be stopped as soon as possible. The vines with bright colored flowers aren’t as problematic.
Reducing crop yields and destroying landscaping aren’t the only reasons to control these two vines. Both contain toxic alkaloids that are poisonous to livestock. Usually livestock won’t eat them, but that’s not ideal either. Weeds that are unpalatable to livestock will usually spread through a pasture.
Seeds are toxic too. They also contain alkaloids and other toxic substances. Some folks like to experiment with them. They shouldn’t any more than they should sample poisonous destroying angel fungi. When I was in college some people ate or smoked morning glory seeds. It’s a good way to get yourself killed.
Even the stems have chemicals that can be sensitive to some people. Therefore, it’s a good idea to wash your hands and arms thoroughly after cleaning up morning glory or bindweed vines. I’ve heard this sensitivity is rare, but why play with fire.
I’ve been hesitant to write about plants that might make people sick or worse. However, I’ve received inquiries about nefarious uses of morning glories and I wanted to set the record straight. People should be wary of things they read on the internet. One stupid experiment can ruin or end your life.
Ted Manzer teaches agriculture at Northeastern High School (email@example.com).
A box of expired seed was dumped behind a supermarket here a few years ago. Morning glory appeared the following year. I do not know if they came from the seed, but I do not know where else they would have come from. The vines started to grow like blue dawn flower, but with only a few white flowers. They are pretty, but have taken over a large part of the riparian area in which they are growing. There is no way of knowing if their seed is spreading downriver.