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Master Gardener Journal  


A   B O U N T I F U L   G A R D E N



Speaking of Spinach

by Linda Trujillo,
Master Gardener


BOTANICAL NAME
Spinacia oleracea (Spinacia comes from the Latin word for spine, and oleracea means edible plant).

COMMON NAMES
Spinach (English), épinard (French), spinat (German), spinace (Italian), espinaca (Spanish), and hispane (Arabic).

ORIGIN, HISTORY AND FOLKLORE
The actual origin of this widely grown potherb is unknown, but we do know that it was cultivated in Iran more than 2,000 years ago. In fact, the word "spinach" is derived from the Persian word for "green hand." Spinach was introduced to China in the 600s and to Spain in the 1100s. By the 1200s, the prickly seeded varieties were known in Germany. Spinach has been grown in Europe since the 1400s and came with the first settlers to America. The first description of a smooth-seeded variety was recorded in 1552. By 1806, spinach was listed in American seed catalogs.



DESCRIPTION
Spinach is a hardy, cool weather member of the Chenopodiaceae (Goosefoot) family. Spinach has a deep taproot and a shallow yet extensive branching root system, with most of its feeder roots in the top few inches of the soil.

The plant produces a rosette of fleshy, non-hairy leaves that tend to be broad and tender. There are two basic leaf types: 1) smooth or flat and 2) crinkled or savoy. Hybrid varieties now offer a semi-savoy type, which has a smoother, less crinkled leaf texture. Leaf shapes include round, oval, arrow-shaped, or triangular; borne on edible stems ranging from 1 to 6 inches long.

Spinach is considered to be dioecious, which means that male and female flowers appear on separate, unisexual plants. However, according to TaylorÕs Guide to Heirloom Vegetables by Benjamin Watson, the heirloom variety Bloomsdale Longstanding "was bred from a single monoecious plant."

Greenish-white, inconspicuous flowers appear in clusters along the seed stalk, which can reach several feet in height. Flowers are wind pollinated.

There are two types of seeds: round and prickly. Seed type can be an indicator of leaf type. Prickly seeds typically produce smooth leaves, while smooth seeds tend to produce savoy leaves.

HOW TO GROW
Spinach can be planted from mid-September through the end of February. It tolerates partial shade, but grows best in full sun. The optimum daytime growing temperature ranges between 50 and 60 degrees Fahrenheit.

Spinach does well in a variety of soil textures, but prefers fertile, well-drained soil with a pH of 6.0 to 7.5. Prior to planting, prepare the bed by enriching it with organic matter and turning it to loosen to a depth of 18 inches. Be sure to deeply water the bed prior to planting, since adequate moisture is essential to quick germination, and overhead watering can lead to seedling diseases.



Some experts suggest chilling seeds for 1-2 weeks prior to sowing, since germination is often slower in warm soils. Sow seeds 2 inches apart, 1/2 inch deep, and thin seedlings to 4 to 6 inches apart. If you plant in rows, space them at least 12 inches apart. If you practice intensive gardening methods, thin seedlings to 6 inches apart in all directions. For square-foot gardening, Mel Bartholomew recommends 9 plants per square foot.

I prefer to space the plants at least 6 inches apart because overcrowding can lead to stunted growth and premature bolting. Lack of ample growing space also increases the plant's susceptibility to disease and pests.

Soil temperatures for germination range between 45 and 75 degrees Fahrenheit. Germination usually takes place in 7 to 10 days. Once the seedlings have emerged, water plants deeply and regularly at ground level to provide uniform moisture and keep the foliage dry. Wet foliage can create a favorable environment for pests and disease.

While all gardeners agree that spinach is a heavy feeder, few agree on when and how often to apply nitrogen fertilizer. Spinach can be sensitive to fertilizer burn and its root zone is relatively shallow, so I carefully side-dress my plants with a complete fertilizer every 4-6 weeks to keep the plants healthy and the leaves dark green and growing.

Spinach can be grown successfully in containers. Be sure to choose plant varieties suited to container gardening and use containers with ample root zone room and good drainage.

VARIETIES AND SEED SOURCES
For best results, select varieties that are resistant to disease and have the leaf texture you prefer.

I usually plant several varieties throughout the long growing season. My current favorite is America, a savoy variety with a thin, medium- to dark-green, arrow-shaped leaf. Originally introduced in 1952, this variety is extremely productive and relatively slow to bolt. The leaves have a wonderful sweet and peppery flavor, which remains even after steaming. It also stores and freezes well.

Bloomsdale Longstanding (savoy) and Indian Summer (semi-savoy) are two of my all-time favorites. Correnta (smooth) is a recent addition to my growing list because it is extraordinarily slow to bolt, which makes it a natural for late season planting. Its thick, roundish, dark green leaves are tender and sweet.

My preferred seed sources include Seeds of Change and Botanical Interest.

PESTS AND DISEASES
Fungal leaf diseases can appear if the weather is wet or humid. Downy mildew produces yellow spots on the topside of leaves and mold on the underside. The symptoms for cucumber mosaic virus include yellow leaves and stunted growth.

Aphids, nematodes, wireworms, cabbage loopers and other caterpillars can sometimes cause problems. If you spot the telltale sign of leafminers, chances are it's the larvae of a tiny black fly with yellow markings. Remove and destroy all affected leaves to interrupt the fly's life cycle.

Another possible pest is the spotted cucumber beetle, which is about 1/4 inch long with a black head and spotted, yellow body. The larvae are about 1/2 inch long and black at both ends. The larvae feed underground and the adults feed aboveground. This pest is a vector for bacterial wilt and mosaic virus.

WHEN TO HARVEST AND HOW TO STORE
Spinach matures in 30 to 50 days, and is tastiest when picked young and sweet. Begin harvesting when the rosette has six or more leaves at least three inches long. To harvest a few leaves for use fresh, pinch off the outer leaves about an inch above the base of the plant.

For larger quantities, you may need to harvest the entire plant. Take a sharp knife in one hand and grab hold of the plant with the other and cut a swath through all the leaves about an inch above the base of the plant. This method is sometimes called "cut-and-come-again," because the plant will put out another set of leaves. When harvesting the entire plant, root and all, you may want to have a bucket of water nearby so you can dunk it in and remove any large amounts of dirt.

My standard short-term storage practice is to wash the leaves, shake of the excess water and lay them somewhat overlapping on a strip of paper towel. I then tightly roll up the spinach in the paper towel, place it in a freezer bag and put it in the vegetable drawer of my refrigerator. I've found that it usually keeps for a week or two.

My long-term storage practice is to wilt the washed spinach leaves in a dry pan for a minute or two and then transfer them to portion size freezer bags. I squeeze out as much air as possible, seal the bag and place in the freezer.

SEED SAVING
According to Susan Ashworth, spinach seeds retain a 50 percent germination rate for 5 years when stored under ideal conditions. Seed saving for home gardeners is a difficult process, so please consult her book Seed to Seed for detailed instructions.

USES
Spinach is absolutely wonderful when freshly picked and eaten raw or quickly steamed. It can also be dried, crushed and used similar to other dried herbs.

NUTRITIONAL VALUE
Spinach has twice as much iron, calcium, potassium and protein as other leafy greens. It is an excellent source of the antioxidants vitamins A and C, as well as the B vitamins thiamin, niacin and folic acid. It also contains the carotenoids lutein and zeaxanthin.

HEALTH BENEFITS AND CONCERNS
Spinach contains oxalic acid, which can interfere with the absorption of calcium and magnesium. In addition, if grown with large amounts of ammonia fertilizers, nitrate concentrations may reach near-toxic level.

References:
Ashworth, Suzanne. Seed to Seed. ISBN 0-9613977-7-2 (pp. 76-78).

Sunset Garden Pests & Diseases. ISBN 0-376-03302-9

UC IPM Pest Management Guidelines: Spinach is available online at http://axp.ipm.ucdavis.edu/PDF/PMG/pmgspinach.pdf

Cooking Conversions

One pound of raw spinach yields approximately 1 cup cooked.

For each salad serving or cooked side dish serving, plan on starting with 1-1 1/2 cups raw.


Maricopa County Master Gardener Volunteer Information
Last Updated October 4, 2003
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, University of Arizona Cooperative Extension, Maricopa County
© 1997 The University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension in Maricopa County
Comments to Maricopa-hort@ag.arizona.edu 4341 E. Broadway Road, Phoenix, AZ 85040,
Voice: (602) 470-8086 ext. 301, Fax (602) 470-8092