How to Manage Pests

Pests in Gardens and Landscapes

Time to plant

Onions: Temperature plays an important role in the development of onion bulbs. However, in order to initiate bulb formation, day length is more critical. Each onion variety has a critical day length for inducement of bulbing regardless of temperature or plant size. Short-day onions require day lengths of 12 to 14 hours. Long-day varieties require 14 to 16 hours of day length. Growing onions at less than critical day length results in formation of new leaves but no bulbing. When short-day onions are grown under long-day conditions, bulbing develops while the plants are very small and results in small bulbs (great for cocktail onions).

Garlic: Garlic is generally best planted in the fall for largest size bulbs at harvest. Later planting is acceptable but bulb size may be smaller. Bulb formation begins in response to lengthening days. In cold-winter areas, mulches around the plants will protect them from severe cold.

Garlic and onions are suitable for a small garden if compact varieties are grown. In a suitable climate, green onions may be planted more than once a year for a continuous harvest.

Planting Dates for Onions and Garlic*

CALIFORNIA Transplant or direct seed

North and North Coast
Monterey County north

Oct.–Dec.
(garlic)
April–July
(green onions)
Jan. - Mar.
(bulb onions)

South Coast
San Luis Obispo County south
Oct.–Dec. (garlic)
All year
(green onions)
Feb.–March
(bulb onions)
Interior Valleys
Sacramento, San Joaquin valleys
Oct.–Dec.
(garlic)
Aug.–Dec.
(green onions)
Nov.–March
(bulb onions)
Desert Valleys
Imperial and Coachella valleys
Sept.–Nov.
(garlic)
Sept.–Jan.
(green onions)
Oct.–Nov.
(bulb onions)
*Areas are large, so planting dates are only approximate, as the climate may vary even in small sections of the state. Contact experienced gardeners in your community and experiment on your own to find more precise dates.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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