1. Q. Each year my spring-planted spinach sends up a flower stalk about the time I think it is ready for harvest. What causes this and what can be done about it?
A. Spring-planted spinach hurries into its flowering phase which stops production of edible foliage. Flowering of spinach is affected by length of day, temperature and variety. Bold resistant varieties, often called long standing, should be used in the spring. Plant as soon as possible in the early spring and not later than 6 to 8 weeks before daytime temperatures are expected to average over 75 degrees F. Bolting is usually not a problem in fall planting which should be about 4 to 6 weeks before the first average frost occurs.
2. Q. How do I keep my spinach growing vigorously instead of slowing down?
A. Spinach responds to liberal applications of a nitrogen fertilizer which stimulates growth and production of leaves. Applications of ammonium nitrate or sulfate applied as a sidedress at the rate of 2 to 3 tablespoons per 10 feet of spinach row will hasten growth and improve spinach yields. Apply when the plants are about 2 inches tall and again after the first harvest.
3. Q. Should spinach be harvested by removing the outer, older leaves or by pulling the entire plant?
A. This depends on whether it is a spring or fall-planted crop. In the spring, spinach will go to seed quickly so the best harvesting method is to pull the entire plant. When planting in early fall for winter harvesting, harvest the outer leaves and allow the plant to continue to grow and produce additional foliage.
4. Q. I've heard that spinach is extremely high in minerals and vitamins but also contains high levels of something which can cause problems. Is there any truth to this?
A. Spinach contains high concentrations of oxalic acid which can interfere with the utilization of calcium or magnesium in the diet. The same is true for rhubarb and Swiss chard.
5. Q. Can New Zealand spinach be grown successfully?
A. Yes. New Zealand spinach is a low-growing, groundcover plant which spreads 3 to 5 feet. New Zealand spinach should be started indoors in peat pots and transplanted after danger of frost in the spring. Young, tender stems and leaves can be harvested through the summer in most areas.
6. Q. What is Malabar spinach?
A. Malabar spinach, sometimes called summer spinach, is an attractive, glossy-leaved vine that grows rapidly during warm weather and produces edible leaves and shoots in 70 to 80 days. Since it grows a vigorous vine, it should be trained against a fence or wall. Young leaves and growing tips can be harvested throughout the summer. Seed may be saved from the plant in the fall for replanting in the next garden. The leaves are used fresh in salads or cooked as greens.
7. Q. I have grown spinach before and realize that it should be grown during the fall-winter months. My neighbor grows a vining spinach during the summer but the leaves do not look the same.
A. The so-called "New Zealand spinach" is Tetragonia expansa, a member of the Aizoaceae (carpet-weed) family, and is not a variety of spinach, Spinacia oleracea. "New Zealand spinach" is a large, much branched, spreading plant that produces a succession of small, very thick and fleshy pointed leaves on round, fleshy stems. The leaves and tips of the branches are used like spinach. This plant will be damaged by cold weather so you should now plant spinach spinach, i.e., the real spinach which survives mild winters.
8. Q. The foliage on my spinach plants developed white, ruptured areas underneath the leaf and a faint yellow color on the upper side of the leaf.
A. This is white rust, a fungus that causes severe loss of foliage. It is favored by cool, moist weather. There are resistant varieties. The varieties Hybrid 7, Coho and Dixie Market resist white rust.
9. Q. The foliage on my spinach plants has developed a bluish- gray material underneath the leaf. The leaves dried quickly.
A. This is blue mold of spinach caused by a fungus. The Bloomsdale varieties are very susceptible and should not be grown in the south.
10. Q. White spots develop quickly on the upper sides of my spinach leaves, then form holes. The leaves look ragged.
A. This is either Cercospora leaf spot or Anthracnose. These fungal diseases attack spinach causing the described symptoms. A good fungicide program will control these fungi.
11. Q. I planted spinach this fall, yet the plants died soon after coming up.
A. An excessively high soil temperature is probably killing the plants. Plant spinach when the soil temperature reaches no higher than 75 degrees F. during the daytime. Soil temperature can be determined by placing a soil thermometer in the upper inch of the soil and reading it at noon. Also, once plants become established, maintain a moisture level around them by light, periodic sprinkling.
12. Q. Small, clear green or sometimes dark colored insects are a real problem on my spinach every year. How should I control them?
A. Any small clear-bodied insects are probably aphids, often called plant lice. They are difficult to control in spinach because they get under the curled or crinkled leaves. Insecticides should be applied with large quantities of water to the underside of the leaves. Applications of a general purpose insecticide such as Malathion begun early in the season generally results in good control. Aphids may also be washed off with a vigorous stream of water, but avoid damaging the plant.