Bindweed: A Garden Menace
Bindweed, pretty on the outside, pure chaos on the inside. This late-season menace is creeping into gardens everywhere, and the story behind it is wilder than you’d think. Want to know how it got here… and why it won’t leave?
Space Invaders: Bindweed
Late in the year, we encounter one of the most irritating warm-season weeds: bindweed. Smothering, covering, and drowning your plantings - this plant sure is a headache. The invasive field bindweed, Convolvulus arvensis, originated in Eurasia and traveled all over the world, seeking out high-disturbance, sunny areas with high soil fertility, aka your garden. Thought to be first introduced to the US via Virginia in the 1700s with contaminated crop seed, field bindweed has steadily seeded and wound its way throughout North America. It is considered a noxious weed for agriculture, causing millions of dollars of damage and crop loss each year as it smothers its neighbors. A member of the morning glory family, don’t let its cottage-style charm fool you - it’s a menace.
Looks Like Trouble
A creeping or climbing perennial vine with aggressively sinuous rhizomatous roots, once field bindweed makes its appearance in a garden, it’s tricky to eradicate. Convolvulus arvensis grows up to 3’+ tall with arrow-shaped leaves alternating along the stem of the vine. The flowers are trumpet-shaped in shades of pink and white, typically open in the cooler hours of morning and evening. In its native habitat, it prefers dry areas with humus-poor, nutrient-rich, alkaline soils. In the US that translates to roadsides, farmland, ditches, grassy slopes, and pastures, even overrunning desolate parking lots, rhizomes taking hold in cracks in the pavement.
Oh, but there’s more… meet the confusing cousins.
Hedge bindweed
Another noxious weed, Calystegia sepium, is a relative of field bindweed that arrived in the US from Europe. It’s a perennial vine growing up to 10’ with white trumpet flowers growing on dull-green, arrowhead-shaped leaves. Generally, the leaves are larger than those of field bindweed, with slightly larger trumpet-shaped flowers that are exclusively white, and the plant grows taller. In our book, it’s just as annoying and persistent as field bindweed, but this one grows even larger.
Morning glory vine and Moonflower
Members of the same family but of the genus Ipomoea, these cottage garden favorites were growing along fencelines and over your grandmother’s mailbox in your childhood. Morning glory flowers can be found in shades of blue, white, and pink, while moonflowers are bright white. Both have the twining stems growing 10’ or more, alternating foliage, and trumpet-shaped flowers. Unlike bindweed, morning glory flowers are annuals and depend on seed dispersal to return year after year. In certain parts of the country, they have naturalized but are far easier to remove. Since they are annuals, just weed them out before they’ve set seed in late summer and early fall, and you should be good to go.
Milkweed vine
A native perennial, Cynanchum laeve is the milkweed vine. The twining nature of this vine and arrowhead-shaped leaves can lead folks to confuse our endemic milkweed vine with invasive field bindweed. Unlike members of the bindweed family, milkweed vine flowers are umbellate clusters, and when the stems are broken, they exude a milky sap. As you might have guessed, Cynanchum laeve is in the milkweed family and supports our native Monarch butterflies. If you find it in your landscape, what a blessing, because it’s endangered in PA but commonly found throughout the East Coast. Even if you don’t want it there, good luck, because those root systems can really spread out and dig in, popping up even if you rip it out. We’re big fans of letting it wind and weave over sturdy, evergreen shrubs. Milkweed vine prefers disturbed soils, full sun, and medium soil moisture along fence rows, cultivated fields, river banks, and open meadows.
Why is field bindweed noxious?
The twining vines of field bindweed aggressively grow in disturbed areas and can easily smother and outcompete ornamental plantings within weeks of their summer emergence. For those who find the flowers cheerful and aren’t concerned with the vines taking over one area of a planting bed, the fruits produce 1-4 seeds per flower, averaging 550 seeds per plant. These seeds are consumed by birds, which then spread them far and wide. In California, seeds over 60 years old have been found to remain viable. If this wasn’t enough, the real charge against invasive bindweed is its persistent and extensive root system. The vertical roots have been found to go as deep as 20’ into the soil. However, what is truly impressive is the horizontal root mass in the top 1’ soil layer that aggressively colonizes the soil, producing 1.5-2 tons of root mass per acre in field crops. If this plant were edible, we’d probably be all for it, but what this really means is we’ve got a tough, adaptable weed that only requires a mere two inches of rhizome left in the soil to resprout a whole new plant and a seed that lasts decades.
How do we get rid of it?
As with all things in life, prevention is the best method. If you see a new seedling emerging in the garden, don’t wait; pull it out immediately. The longer the seedlings can establish a root system, as soon as 3-4 weeks after their emergence, the more perennial the root system.
Cultivation
Consistent, continuous soil disturbance to remove rhizomes is effective when implemented over a 3-5-year period. Remove all broken roots from the soil as you cultivate. Remember, only 2” of rhizome left in the soil can sprout a new plant. Rhizomes should be burned, bagged, thrown in the trash, or left to shrivel up on exposed, sunny, impervious material. If ornamental plants are present, the bindweed rhizome intermixes with the roots of the preferred ornamental plants, making cultivation as an elimination protocol ineffective.
Cutback
Consistent, timely cutbacks of the bindweed top growth can weaken the plant and eventually kill it over a 7-10 year timeline. Cut the top material all the way to the ground, remove all parts, and place it in a burn pit or on sunny concrete to kill the material. Do not place it in the compost bin. If the plant is allowed to grow for several weeks throughout the summer, rhizome growth will expand exponentially, pushing back the elimination calendar. Consistency is the key to making this effective.
Smothering
Smothering field bindweed with plastic, thick cardboard, or landscape cloth can help control its growth. To ensure efficacy, smother the plant with the chosen material, excluding all light from reaching the plant and the soil below. Overlap the edges of the material so plants don’t stretch and break through the material edges. Any holes that allow light to reach the soil, whether with low coverage, purposefully added for ornamental plants, or accidental, will encourage new bindweed shoots to emerge. To improve appearance, a mulch can be applied above the smothering material. It takes 3 years for light exclusion to kill bindweed, and it should be monitored to ensure no emergence occurs. According to the University of California, complete plant death should occur in 3-5 years.
Chemical control
Herbicides can be used to suppress bindweed but are generally ineffective at completely eliminating the plant. Use of broad-spectrum herbicides like glyphosate, alternated with more targeted broadleaf herbicides, may prove effective. For a list of herbicide recommendations for turf grass, ornamental beds, and nonfood crop lands, please refer to the list provided by UC IPM. Follow the herbicide manufacturer's directions for proper use and storage.
A Trial in our Trial Gardens
We’re not just speaking theoretically on this noxious weed - we’ve got one spot in our trial gardens where we’ve been trying to beat back bindweed for years. We choose to cut it routinely, right down to the ground, and keep an eye on the bindweed throughout the season. We know we’ll never be rid of it; it grows everywhere in the landscape surrounding our nursery, and the birds love our trees. But for everyone else battling this Space Invader - good luck! It seems we’re all in this battle together.
Read More:
University of California IPM “Field Bindweed”
Penn State Extension “The Noxious, Persistent, Invasive, and Perennial Bindweeds”
Missouri Plants “Cynanchum laeve”
The Exerces Society for Invertebrate Conservation “Milkweeds”
