The new farmer called his county agent to ask what to do about the bindweed he had discovered in a field. Without a moment’s hesitation, the county agent replied, “Sell the farm and move.”
That’s the kind of tale that field bindweed inspires. Convolvulus arvensis, also known as creeping jenny and perennial morning glory, is one of the most pernicious weeds farmers have to deal with. It is found in virtually every state of the U.S., except for a few in the southwest. It smothers small plants, twines up and pulls down tall plants, tangles up machinery, and spreads like wildfire.
Listen to this description of the awesome power of bindweed, from North Dakota State University: Field bindweed can develop extensive above and below ground growth soon after germination. A single plant six months after germination produced 197 vertical roots, each at least 4 feet long for a total of 788 feet, while growing in a large container. Plants had 34 horizontal underground roots coming from the tap root, which averaged 4 feet in length and gave the plant 136 additional feet of growth. These 34 roots produced 141 new shoots which established as individual plants. The root system of field bindweed is extensive. Roots of established plants may extend 20 to 30 feet laterally and develop an extensive underground network. Depth of rooting depends on soil type and rainfall. In areas of high rainfall, roots of established plants have been excavated as deep as 30 feet below the surface. Buds along the root system can send up shoots that start new plants.
It is enough to make you want to sell the farm and move. But don’t despair if you have field bindweed. While it may be extremely difficult to eradicate, it can be controlled and confined.
The key to bindweed control is cultivation in dry soil. Cultivating in moist soil will only spread it, as the chopped up roots will all grow into new plants. The best time to cultivate is eight to 12 days after new plants emerge. By then, the plant will be using energy on top growth and cutting that off will begin to deplete the roots. This kind of shallow cultivation or hand weeding needs to take place throughout the entire growing season. It may take 18 to 20 timely cultivations over a two-year period to get a serious bindweed infestation under control. A single deep tillage, 16 to 18 inches below the surface in dry soil, can set bindweed back enough that it won’t interfere with an annual crop.
After cultivating a field with bindweed, equipment must be meticulously cleaned so that pieces of root aren’t carried to another area, where they might root.
Shading is also somewhat effective in reducing bindweed. Putting the field into alfalfa for three or four years may rid it of bindweed. Cereal grains and corn also reduced bindweed growth. Black plastic mulch or landscape fabric can be used to stymie bindweed. But there must be no light allowed to reach it, either between sheets or along the edges. And it can take three or four years of light exclusion to kill the bindweed roots. The best approach would be to cover the bindweed with black landscape fabric, cover that with wood mulch, and leave it for three years.
Bart Hall, an organic farming consultant based in Lawrence, Kansas, had this suggestion: “The small grower actually has the best circumstances of anybody for organic control. The jenny must be ceaselessly hassled for three or four years. Best candidates for the job are poultry, followed by young hogs. Fence off the spot and about an extra 10 feet around it. Bring in enough critters to eat it down to a bare nub and keep it that way. Eventually the bindweed will die permanently.”
To prevent the spread of bindweed, don’t let the plants flower and go to seed. Seed that is 50 years old has been found viable. And an average plant produces 550 seeds. But individual seedlings can be removed by cultivation or hand weeding as they appear; if removed in the first three or four weeks after germination, they will not establish the typical extensive root system.
Herbicides are no better than cultivation - they can suppress but not eradicate bindweed, according to the University of California IPM Project.
In sum, control of field bindweed will take time and patience. “It is not easy and it cannot be accomplished with a single treatment or in a single season,” the UC Pest Management Guideline states. “Effective control requires prevention of seed production, reduction of stored carbohydrates by deep tillage of the root system, competition for light from other plants, and constant vigilance in removing top growth.”