Regional Gardening Reports :: National Gardening Association

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

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If sweet potato plants are heavy on lush foliage but light on good-sized tubers, excess nitrogen is likely the culprit.

Growing Your Own Sweet Potatoes

There's still time to plant sweet potato shoots for late-summer harvests of those golden tubers full of sweet nutrients. Mysterious problems may arise, and here are some approaches to preventing them.

Problem: Stem rot causes young plants to die after transplanting, and survivors develop bright yellow leaves that pucker, wilt, and die. Harvest is of poor quality.
Solution: Plant certified seed of resistant varieties. Rotate the crop so that plants grow in the same soil only once in four years. Avoid overcrowding and overfertilization.

Problem: Foliage is lush but tubers are long and thin.
Solution: Plants received too much nitrogen. Incorporate a balanced fertilizer when planting, and sidedress with a low-nitrogen fertilizer.

Problem: Tubers have a brownish black surface discoloration that is only skin deep and can be scraped off easily. Scurf is most severe on heavy wet soils with a high level of manure.
Solution: Plant healthy sprouts from certified seed stock. Incorporate compost to lighten the soil and provide better drainage. Rotate the crop so that potatoes grow in the same soil only once every four years. Eating quality is not harmed.

Problem: White mold starts on bruised areas and develops into soft, watery rot on stored tubers.
Solution: Plant certified stock of resistant varieties. Avoid bruising tubers during harvest. Cure tubers in a dark, humid, and well-ventilated atmosphere at 80 to 90 degrees for two weeks. Store in a dry, well-ventilated area at 55 to 60 degrees. Avoid overcrowding.

Problem: Tubers are rough and oddly shaped when they are grown in soil that is too heavy.
Solution: Incorporate organic matter to lighten the soil texture.

Problem: Tubers are dry and rough textured when they have endured alternately wet and dry conditions.
Solution: Irrigate deeper and more frequently.

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