Plant veggie starts early to prevent bolting

Last Updated: 
May 7, 2009

EUGENE, Ore. – Note to Oregon home gardeners: Don't put off planting vegetable starts. Warm weather in May and June may increase the likelihood that young vegetable starts in home gardens might “bolt” – that is, they might flower and set seed prematurely before producing their vegetables.

Plants left in the garden from last year are already starting to bolt because of the warm weather, according to Ross Penhallegon, horticulturist with the Oregon State University Extension Service.

"When warm weather follows a period of cool weather – such as this spring – the normal growing cycle becomes compressed, stimulating the plants to produce seeds," he said.

Bolting is often a problem with biennial vegetables, including cabbage and other cole crops, beets and carrots that 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 when 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 3-16ths of an inch) work best," Penhallegon said.

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.

Author: Judy Scott