Tuesday, August 11, 2020
Aug. 11, 2020

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Gardening with Allen: Lack of fertilizer main cause of plants’ fading summer color


My containers and other flowers and vegetables look great until hot weather hits in July. Then they either get straggly or lose their dark green color. Even my lawn is losing color. Is there anything I can do to keep them healthy through the whole summer?

The main cause of color loss in plants is lack of fertilizer. Frequent irrigation washes fertilizer nutrients below the reach of the root system. This is especially true for container plants. I usually give my flowers and vegetables an additional fertilization in early July. If the lawn loses color I give it a half rate feeding.

When older or lower leaves turn yellow, they are suffering from nitrogen shortage. If newer leaves turn yellow with darker veins, it is usually iron deficiency.

I prefer a fertilizer with equal amounts of nitrogen, phosphorus and potassium for flowers and vegetables. A typical analysis is 16-16-16 nitrogen-phosphorus-potassium. Organic fertilizers usually have a lower analysis and are not usually all the same. Lawn fertilizer contains more nitrogen, less potassium and very little phosphorus. Check the analysis label to make sure there is at least a small amount of iron also.

My favorite fertilizer for flowers and vegetables is Osmocote. The fertilizer pellets have been coated with poly covering which has very small pores. When the pellets become wet, the water flows into the pellets and dissolves a small amount of fertilizer, then flows out again. This releases a small amount of fertilizer every time the plant is watered. This results in steady, uniform growth.

Some flower varieties have a tendency to grow rapidly in the spring when they have plenty of fertilizer. Then they look straggly after the fertilizer runs out. When this happens I usually cut them back by about half before I give them another shot of fertilizer.

I feed trees and shrubs in the early spring along with my lawn. They seldom need fertilizer beyond this spring feeding.

One other cause of poor plant appearance is irregular watering. When plants dry out and wilt between water applications they eventually lose leaves and roots and won’t recover completely.