Field bindweed (Convolvulus arvensis)
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Field bindweed, a perennial broadleaf, is considered one of the most problematic weeds in agricultural fields throughout temperate regions worldwide. It is abundant throughout California and grows up to an elevation of about 5000 feet (1500 m). Field bindweed is troublesome in many crops, but particularly difficult in potatoes, beans, and cereals. It can harbor the viruses that cause potato X disease, tomato spotted wilt, and vaccinium false bottom.
The cotyledons (seed leaves) are nearly square, with a shallow notch at the tip. The seedling looks similar to morningglory seedlings, but are much smaller and less deeply notched. Sprouts from underground horizontal stems (rhizomes) are similar to seedlings, but lack cotyledons. Early true leaves are spade or bell shaped.
Leaves of the mature plant look similar to those of the younger plant, but they are lobed at the base. Leaves are attached to flattened stalks that are grooved on the upper surface. Stems grow to several feet long. They trail along the ground or climb on upright plants such as shrubs. Wild buckwheat trailing stems are often mistaken for those of field bindweed.
Flowers bloom from April through October or until the first frost. They are trumpet-shaped and white to purplish white. Flowers close each afternoon and reopen the following day.
Field bindweed spreads from both seed and an extensive underground horizontal stems (rhizomes).