When to plant carrots in Walla Walla, WA

Getting carrots to come up

Carrot seeds are slow, often taking one to three weeks to sprout, and they need the soil surface to stay moist the whole time. They'll sprout in soil as cool as 40 to 45°F, but come up much faster in warmer soil. In the Northwest, the common failure is a crust: rain or watering packs the surface into a crust the tiny seedlings can't push through.

Cover the seeds with a quarter inch of fine compost or vermiculite instead of garden soil, water gently every day or two, and lay a board or burlap over the row until the first seedlings appear. Then remove it right away.

Straight roots

Carrots fork and twist when the taproot hits rocks, clods or hard soil, or when the tip is damaged. Grow them in deep, loose, stone-free soil or a raised bed, and avoid fresh manure. Don't transplant carrots, since damage to the taproot causes forking. Thin seedlings to about 2 inches apart; crowded carrots stay small and tangled.

Flavor, sweetness and frost

Carrots develop their best color and sweetness at about 60 to 70°F. Heat and drought increase the compounds that make carrots taste bitter or soapy. Cool fall weather and light frost make them sweeter as the roots store more sugar. That's why fall carrots taste so good here.

Carrot rust fly

The carrot rust fly is the main carrot pest in the Northwest. The adult is a small fly; its larvae tunnel through roots, leaving rusty brown trails. There are two or three generations a year: the first flies appear from about mid-April to June and a second wave in August and September.

Insect netting or row cover, laid over the bed from sowing until harvest and sealed at the edges, is the most reliable defense. Sowing after the first generation, in early June, also avoids much of the damage. Move carrots to a new bed each year.

Water and soil

Carrots grow best in sandy or loamy soil with a pH of about 6.0 to 6.8. Water evenly. A heavy soak after a dry spell can split the roots. Keep the shoulders covered with soil so they don't turn green in the sun.

Harvest and storage

Pull carrots when the shoulders are about ¾ inch across. Cut the tops off right away, since leaves draw moisture from the root. In the fridge, carrots keep for weeks; in a cold, humid spot near 32°F, they last for months. West of the Cascades you can also leave fall carrots in the ground under a thick mulch and dig them through winter, as long as voles and rust fly aren't a problem.