Bindweed in Desert Gardens

Seasoned desert gardeners know what problem field bindweed (Convolvulus arvensis) can cause.

In the same family as morning glory, field bindweed, like many invasive plant species, is an import from Europe. The family convolvulus also gives us sweet potatoes and Mexican jicama (pronounced hick-ah-mah).

Bindweed can reproduce either by seed or rhizome. Seed leaves are almost square with a little notch at the end of the leaf. If the plant sprouts from a rhizome, there will be no seed leaves.

When the true leaves appear, they will be spade shaped, or bell-shaped. Flowers may be white or purplish white and trumpet-shaped. They will close each night and open the next day (unlike domesticated morning glory flowers, which last only a day.

Many gardeners, thinking it is indeed morning glory, will encourage the plant to grow. Unfortunately, in addition to being invasive, bindweed grows deep taproots, often 20 feet or more in length. The combination of deep taproots and multiple methods of reproduction make the plant very difficult to eradicate.

Chopping the root system will, more often than not, only spread the rhizomes and allow them to flourish.

In fact, field bindweed is happiest (and most aggressive) on newly-cultivated land.

Once established, bindweed roots will entangle the roots of surrounding plants, strangling and killing the plants. It’s aggressive above-ground tendrils grow very quickly and will entwine and kill or damage garden plants.

Unminded, bindweed will also form thick mats across the ground, preventing other desirable seeds from germinating or growing, and killing seedlings.

It has become a bane to agriculture, particularly in the western and southwestern U.S., although it is prevalent across the entire continent of North America. It has been found growing at sea level and even above 10,000 feet.

Eradicating Bindweed

Unfortunately, there are currently no herbicides known to kill bindweed, although there are several herbicides on the market that may at least bring bindweed under control. Chemicals such as dicamba and glyphosphate have been successful in suppressing it, but not in eradicating it. There is currently a fungal herbicide that is being tested that has had some effect on eradication. It is not yet on the market.

The weed is so tough and aggressive, and has such a strong root system, that the only way to eradicate it permanently is to exhaust the plant by depriving it of carbohydrates. This is done by continually removing the above ground parts of the plants and totally discarding them. Deep tilling or plowing may actually encourage the plant to grow. However, if deep tilling is used, and the roots are left to dry in the sun, it may help to control it.

It may take several growing seasons to get bindweed under control, and probably longer to completely eradicate it.

Biological Control

Currently there are two biological entities being tested. One is a defoliating moth and the other is a gall mite. Both are species specific and both have been released in selected areas of the U.S. and Canada. However, some states, like California, have not approved the use of these biological weapons.