Spinach
Spinach is Spinacia oleracea, "spina" in Latin meaning spiny
fruit and "oleracea" meaning herbaceous garden herb. It is
a member of the Chenopodiaceae (goosefoot) family which also includes
Swiss chard and beets. It is a low-growing fleshy-leafed annual that
forms a heavy rosette of broad, crinkly tender leaves. The glabrous
(non-hairy) leaves, which are the edible vegetable portion, are ovate
(oval, but broader toward the base) to orbicular (round) in shape with
the lower leaves being wider and the higher leaves being narrower. The
leaves may be savoyed (puckered) or smooth. Leaf stems are also edible,
but less preferred because of toughness. The savoy leaved plants are
usually preferred for fresh marketing; the smooth for processing. The
leaves are lobed at the base and sometimes lobed on their sides. It
is a good source of vitamin C, vitamin A, and minerals, especially iron.
History
Spinach originally came from Persia (now Iran) where it was
known as "aspanakh".
By the 1300s, it had spread to Europe and Britain where it was popular
in religious communities, particularly during Lent.
It was being cultivated in North America by the early part of the 19th
century. In recent times, it has been popularized by the cartoon character
"Popeye", who attributes his amazing strength to a daily diet
of the green leafy vegetable.
Spinach Plant
Spinach plants should be well-developed and stocky. They
should have fresh, crisp, clean leaves of good green color. Straggly,
long-stemmed, overgrown plants or plants with seedstalks are undesirable.
Plants with coarse leaf stems may be tough. Wilted spinach, or decaying
spinach (with soft, slimy rot) is undesirable. Small, yellowish-green
heart leaves are not objectionable. Most fresh market spinach is savoy
type, but leaf type (whether savoy or smooth) is not an indicator of
quality.
Growing Environment
Spinach is very hardy and can withstand temperatures as low
as 20 F. It can be the first garden vegetable planted in the spring
since the seed germinates at low temperatures. Spinach thrives in cool,
moist conditions. It does not tolerate hot weather and begins to bolt
or go to seed as daylight lengthens and temperature increases in June.
Two spinach crops are possible in Nebraska; the second can be planted
in late summer for harvest in the fall.
Suggested earliest and latest spring and fall planting dates for different
regions in Nebraska are: Spring Planting Fall Planting
Fresh spinach seed germinates readily at 38-40F and may be planted
with good results when soil temperatures are 50 to 60 F. Higher temperatures
reduce seed germination. Soil temperatures above 85 F will inhibit seed
germination. Spinach seed rapidly loses viability. Fresh seed should
be purchased each year. Spinach should be planted in rows 1 to 2 feet
apart. The seed should be placed 1/2 inch deep and planted to have one
plant every 3 to 4 inches after thinning. One packet of seed will plant
25 feet of row. One ounce of seed will plant 100 feet of row. Commercial
seeding rates are 12-15 pounds per acre.
Spinach requires a soil pH of 6.0 - 6.5 and will not grow well if pH
is below 6.0. Indications of possible soil pH problems include poor
seed germination, yellowing and browning of the margins and tips of
seedling leaves, browning of roots, and generally slow growth or death
of the plants. If soil pH is too high, leaves may show a generalized
yellowing or chlorosis.
Spinach is adapted to a range of soil types, from light and sandy to
silty clay loams. In heavier soils, spinach should be grown on raised
beds to improve drainage for the shallow-rooted plants. Seedling damping
off can be reduced by use of raised beds. After seeding, the soil should
be kept uniformly moist. When irrigating the garden, apply water in
the morning so that the foliage is dry before dark. Apply sufficient
water to moisten the soil to a depth of six inches. A uniform supply
of soil moisture is required to produce high quality, tender spinach.
Spinach growth starts slowly and then accelerates during the final
21 days before harvest. If a soil test has not been taken, broadcast
5-10-10 fertilizer at 30 pounds per 1,000 square feet before planting.
Spinach should be side-dressed once during the growing season with ammonium
nitrate at 1 pound per 100 feet of row or calcium nitrate at 2 pounds
per 100 feet of row. A total of approximately 150 lb/A of actual N is
recommended, usually applied 1/2 preplant and 1/2 as a broadcast application
3-4 weeks after seeding. Spinach requires fairly high boron (B). Most
soils in Nebraska supply adequate boron for spinach. Spinach plants
can become stunted with dark roots and small, flattened, yellow leaves
when boron is deficient. An application of 1 pound of boron (10 lb/A
of borax) broadcast before seeding should eliminate the problem in subsequent
years. NEVER use boron unless needed and then only in the recommended
amounts. Boron is highly toxic to many other garden plants including
snap beans, cucumbers, peas and strawberries.
Emergence rate varies depending upon soil temperature; time from planting
to harvest also is highly temperature dependent. Generally, most varieties
can be harvested 45 to 50 days after planting. Spinach can be harvested
from the time the plants have five to six leaves until just before seedstalk
formation.
Varieties of Spinach
Spinach varieties are separated into types with flat leaves, leaves
that are semi-savoyed (crinkled), or those that are heavily savoyed.
The flat-leafed types are used primarily by the processing industry
since soil particles are easier to wash off. The thick leaves and ease
of washing also make this type attractive to certain fresh market consumers.
Whatever type, fresh spinach should be crisp, succulent and dark green,
with a minimum of stems.
During the past ten years, a major change has occurred in the type of
spinach grown, primarily due to advances in breeding mildew resistance
into types adapted to North America. The hybrid varieties show superior
vigor, uniformity, bolting resistance and disease resistance compared
to the older varieties. The more upright growth habit makes harvesting
easier and keeps the leaves cleaner.
Seven R is a standard, semi-savoyed cultivar
that is best for early spring and fall plantings. Plants are large and
quick-growing. The erect leaves are good for mechanical harvesting.
It is resistant to both race 1 and race 2 of downy mildew.
Marathon has a savoy leaf. It is better than Seven R for spring plantings
since it is slower to bolt (form flower stalks) in warm weather. The
leaves are large, dark green, semi-erect and long standing. It is used
for both fresh market and processing from late winter and spring plantings.
Melody F1 is a semi-savoyed type. Plants are large and quick growing
with very deep color. Leaves are thick and rounded. It is resistant
to downy mildew and cucumber mosaic virus.
Vienna F1 has large, savoyed leaves forming an erect plant type. It
is best planted in the fall as it tends to bolt in spring plantings.
Grandstand has semi-savoy leaves, is long-standing and semi-erect. The
leaves are medium large and medium green. It is resistant to downy mildew
and mosaic and is used in the spring, primarily for processing.
Tyee F1 is becoming a new standard for savoyed spinach. The leaves are
dark green with an upright growth habit that produces cleaner leaves.
It is a bit slower growing than some other savoy types but stands well
in hot weather because it is slow to bolt. It is good for a spring crop.
It also is tolerant to downy mildew races 1 and 3.
Long Standing Bloomsdale is a heavy-savoy type, adapted for late spring
and early summer harvest. Leaves are dark green and medium large. Plants
are medium large and erect. It is an older variety. Other Bloomsdale
types, such as Long Standing Savoy #653, have been selected for earlier
maturity and slow bolting.
If growing spinach for shipping, the savoy varieties are best because
they pack less closely than the smoother types and retain market quality
better. They are slower to wilt or turn yellow after harvest. Smooth-leafed
varieties are easier to clean and prepare for canning or freezing. Contact
the local Cooperative Extension office for additional information if
you are considering growing spinach for wholesale shipping.
Spinach is shallow rooted. Cultivation to remove weeds must be shallow
to minimize damage to the roots. A few herbicides are available for
commercial production. For smaller plantings, hand weeding is recommended.
Harvesting and Storage
Spinach can be harvested until seedstalk formation. Spinach
planted for early harvest is subject to bolting as daylight lengthens
in late spring and early summer.
Spinach is harvested by cutting the stem below the head or rosette of
leaves. The crinkled leaves should be rinsed thoroughly in cold water
to remove any grit soil particles. The leaves are then bunched. Remember
that fall spinach is very hardy and not easily damaged by frosts. Harvest
dark green, tender leaves that are 3 to 6 inches long. In the home garden,
start by picking the outer leaves and then harvest the newer leaves
as they reach the desired size. Spinach not needed immediately for eating
is best left in the field until severe freezing is forecast. Harvested
spinach can be kept in a moisture-retentive container in the refrigerator
for as long as 40 to 50 days.
Information provided by Oregon State University's Extension http://osu.orst.edu
