How to discourage your veggies from bolting

CORVALLIS - Warm weather in June may increase the likelihood that young vegetable starts in home gardens might bolt, or flower and set seed prematurely, before producing the vegetable for which the plant is grown. When warm weather follows a period of cool weather, the normal growing cycle becomes compressed, stimulating the plants to produce seeds, explained Ross Penhallegon, horticulture agent with the Oregon State University Extension Service. And since biennial plants are grown for their roots, stalks or leaves, "bolting" renders parts from these plants useless in terms of food production.

Bolting is often a problem with biennial vegetable plants including cabbage and other cole crops, beets, and carrots. Biennial vegetable plants ordinarily take two growing seasons to mature, flower, set seed and die. Gardeners normally harvest the vegetables during their first year of growth, before they set flower and seed, or bolt.

Annuals including celery, chard, onions and spinach also bolt after cool springs are followed by very warm weather.

To help vegetables in your garden from premature bolting, Penhallegon advises home gardeners to select smaller plants when buying vegetable transplants.

"Usually, transplants with stem diameters less than the thickness of a pencil (about 3/16 of an inch) work best," says Penhallegon.

Transplants thicker than a pencil are more likely to bolt if the weather turns warm after planting, he said. Biennial transplants can also bolt if they are exposed to warm temperatures before their transfer to the garden environment. So don't put off planting those starts.