Horticulture/Spinach

Spinach is an important leaf vegetable, now grown throughout the temperate regions of the world. It is most productive in cool seasons and climates, since heat will cause the spinach to bolt.

Description
Spinach (Spinacia oleracea) is a flowering plant in the family ../Amaranthaceae/, native to central and southwestern Asia. It is an annual plant (rarely biennial plant|biennial), which grows to a height of up to one metre. The leaves are alternate, simple, ovate to triangular-based, very variable in size from about 3-30 cm long and 1-15 cm broad, with larger leaves at the base of the plant and small leaves higher on the flowering stem. The flowers are inconspicuous, yellow-green, 3-4 mm diameter, maturing into a small hard dry lumpy fruit cluster 5-10 mm across containing several seeds.

Growing Conditions
Spinach is a cool-season crop, and so should be planted either in early spring (just as the soil warms) or in fall. Fall plantings will overwinter into spring for an early crop, and is also well-suited to winter greenhouses and frames.

Planting can be done in situ, in cellpack, or in containers. It is well-suited for growing in flats only for baby greens production.

Varieties
A distinction can be made between older varieties of spinach and more modern varieties. Older varieties tend to run up to seed too quickly in warm conditions. Newer varieties tend to grow more rapidly but have less of an inclination to run up to seed. The older varieties have narrower leaves and tend to have a stronger (although more bitter) taste. Most newer varieties have broader leaves and round seeds.

There are 3 basic types of spinach:
 * Savoy has dark green, crinkly and curly leaves. It is the type sold in fresh bunches in most supermarkets. One heirloom variety of savoy is Bloomsdale. Bloomsdale is also somewhat bolt resistant.
 * Flat/smooth leaf spinach has broad smooth leaves that are easier to clean than savoy. This type is often grown for canned and frozen spinach, as well as soups, baby foods, and processed foods.
 * Semi-savoy is a hybrid variety. It has slightly crinkled leaves. It has the same texture as savoy, but it is not as difficult to clean. It is grown for both fresh market and processing. Five Star is a widely grown variety and has good resistance to running up to seed.

Rosemary Stanton, in her Complete Book of Food and Nutrition, notes that silverbeet (or chard), is commonly referred to as spinach, particularly in Australia and New Zealand. Hence, there may be some popular confusion between the two vegetables.

Other species called spinach
The name "spinach" has been applied to a number of leaf vegetables, both related and unrelated to spinach:

Related species

 * ../Chard/ (Beta vulgaris - also known as spinach beet or perpetual spinach.
 * ../Atriplex/ (Orache) - also called "French spinach" or "mountain spinach".
 * ../Chenopodium bonus-henricus/ (Good King Henry) - also called "Lincolnshire spinach".

In Indonesia, the word bayam is applied both to certain species of amaranth commonly eaten as a leafy vegetable, and to spinach, which is rarely seen, only in certain supermarkets but well known from Popeye cartoons.

Unrelated species

 * ../Tetragonia/ (New Zealand spinach)
 * ../Ipomoea aquatica/ (Water spinach)
 * ../Basellaceae/ (Malabar spinach)
 * The greens of various nightshade, legume and cucurbit species are also known as spinach, wild spinach, African spinach or morogo (in Southern Africa).

Harvest
Spinach is often harvested as a baby green or a cut-and-come-again crop. Baby greens can be harvested in as little as 2 weeks after germination.

Spinach loses much of its nutritional value with storage of more than a few days. While refrigeration slows this effect to about eight days, spinach will lose most of its folate and carotenoid content. This is worth considering when purchasing spinach out of season. If the product has been "in transit" (picked, cleaned, shipped and shelved) for more than one or two days it will need to be used almost immediately to have much nutritional benefit. This is in spite of the taste and appearance of the plant which may still seem fine.

Fresh spinach should be cleaned thoroughly and then can be stored loosely in an unsealed bag in the crisper tray of the refrigerator for a few days. Even at 4°C, spinach loses much of its nutritional value by eight days so for longer storage it should be fresh frozen, cooked and frozen or canned. Storage in the freezer can be for up to eight months.

Pests and Diseases
PEST AND DISEASE Damping off and root rot (fusarium oxysporum, rhizoctonia solani and pythium spp) Damping off disease is usually overcome with the use of disease resistant spinach plants, seed treatments and preplant soil treatments. Damp off can occur throughout the growth of the spinach crop. The disease is caused by several soil fungi including: Fusarium, Pythium and Rhizontonia. Post emergence control of damp off disease is controlled by good water management. Never let water stand in the field. Excess water can cause the same damage with or without a fungi pathogen. The damage includes ground water soaked roots with some top plant curling of the leaves. Damp off damage to mature plants can cause stunting and death. Downy mildew (Peronospora farinose) One of the most important diseases in spinach is the downy mildew or blue mold. Spinach does well in cool, damp conditions. These are the same conditions that downy mildew does best in. The spinach is grown during the fall, winter and spring months when conditions are usually cool. The damp weather is provided with sprinkler irrigation systems when rain isn’t available. The spinach itself provides plenty of humidity with its lush growth of leaves. The first signs of an infection by downy mildew are yellow spots on the leaves. These spots become darker and dry out. Spores form on the bottom of the leaf that have a blue cast to them. Within the spinach downy mildew species there are many variations that infect newly produced spinach plants that are resistant to the older disease species. When treating for downy mildew in spinach, applications should be made before the mildew appears. Once the field is infested efforts to contain it and control are almost impossible. Ridomil Gold/Copper) WP as a foliage application has been effective against downy mildew in spinach. Aliette 80 WDG can be used as an alternate to reduce mildew immunity to other treatments. Anthracnose (Colletotrichum spp.) Applying prevention copper sprays to spinach fields likely to be infested with anthracnose is the only recommended chemical spray. The post emergence prevention efforts of controlling anthracnose include reducing the use of excess sprinkler irrigation. Spinach Crown Mites Spinach crown mites damage new leaves at the heart of the plant. The spinach crown mites are very small and transparent. The damage of crown mites is outgrown by the spinach plant unless the plant is growing slowly. Crown mites can injure the plant to the point where diseases can infect the spinach. Dust will dry out the spinach plant and allow spinach crown mite to multiply. When high populations of crown mites occur and predators are not able to control them, miticides are available. The pesticides that are available include: Agri-Mek; Thiodan and Neemix.