In the Garden:
Southern California Coastal & Inland Valleys
August, 2008
Regional Report

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2862

Onion seed heads are attractive as well as productive.

Problems with the Onion Family

Here are some of the growing problems you may have observed with chives, garlic, leeks, onions, and shallots earlier this year, and what to do so they don't reoccur with this fall's plantings.

Problem: Plants send up flower stalks rather than forming bulbs. This can happen when the bulb sets were too large, planted too early, or kept too warm for too long prior to planting; the soil was allowed to become too dry; or there was a period of cold weather after plants were grown in warm weather for six to ten weeks.
Solution: Plant seeds just before a frost period for a greater variety of shapes, sizes, colors, and flavors. Plant sets that are smaller than 1/2 inch in diameter during or after frost period. Plant larger bulb sets for use as cool-weather green onions. These will bolt with the slightest hint of warmth. Water onions deeply and more frequently to maintain their steady growth.

Problem: Plants stay small and do not produce bulbs if they have been insufficiently fertilized or irrigated, or they are the wrong variety. For example, bunching onions don't produce bulbs.
Solution: Plant bulbing varieties. Apply a balanced fertilizer in late spring, and water onions well until their tops turn brown and fall over, signaling maturation.

Problem: Plants that grow slowly and develop thick necks may result from a phosphorous deficiency or excessive nitrogen or water.
Solution: Incorporate a high-phosphorous fertilizer such as bone meal, finely ground rock phosphate, fish meal, manure, compost, cottonseed meal, or soybean meal. Incorporate organic matter to improve drainage.

Problem: Leaves striped with yellow indicate a manganese deficiency, especially on soils with a pH above 6.7.
Solution: Incorporate manure.

Problem: Leaves that have whitish blotches streaked with silver may have thrips. Heavily infested plants become stunted, the leaves are bleached and die back, and the necks grow abnormally thick. Thrips are worst in hot, dry seasons.
Solution: Plant tolerant and resistant varieties. Dust with diatomaceous earth. Spray with a soap mixture or rotenone. Keep the garden clean of weeds.

Problem: Leaves that are pale or greenish yellow may be deficient in nitrogen, perhaps from leaching out after long, wet periods.
Solution: Incorporate a high-nitrogen fertilizer, blood meal, cottonseed meal, manure, or compost.

Stay tuned for help with troubleshooting disease and pest problems in the August 28 report.


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