Spinach
The cartoon character Popeye attributed his great strength to eating spinach
- maybe justifiably, since this leafy vegetable has a very high iron content. Spinach
(Spinacia oleracea) is a hardy annual
related to beets and Swiss chard that has been used by humans for a long time.
Native to southwest Asia, it was first cultivated in Persia (Iran) over 2000
years ago and used by the Chinese in
the 6th century. Arabs brought it to the Spanish around the 11th century, and it
had spread to the rest of Europe by the 14th century. It was
brought to the Americas with the early colonists. The plant grows a rosette of dark green
leaves, but under warm temperatures and long daylength it bolts, or goes to
seed. The leaves may be eaten fresh or
cooked.
Varieties of Spinach
There are
two basic types of spinach with either smooth leaves or crinkly (savoy) leaves.
The smooth types are normally grown for freezing and canning because they grow
faster, yield more and are easier to clean. The savoy types are preferred for
the home garden and fresh market use because they look and taste better, keep
longer and have less oxalic acid (which can interfere with the utilization of
calcium or magnesium in the diet) than smooth leaf types. Semi-savoy types have
lightly crinkled leaves.
Some
of the newer varieties of spinach, such as Indian Summer and Olympia, are slow
bolting (seed-stalk development is slow even as day length increases), so these
may be desirable for summer crops. Older varieties without this trait are best
used for spring or fall plantings. The old rule of thumb was that prickly-seeded
varieties were best for spring and fall, while round-seeded varieties were
better for summer, but this is no longer true as new varieties of slow-bolting,
round-seeded types have been developed.
Some good choices for Wisconsin gardens include:
- Avon is a semi-savoy type for early spring planting. It has large,
slightly crinkled, dark green leaves and has resistance to blight and
mildew. (44 days to harvest)
- Bloomsdale Longstanding is an older variety, and one of the best
tasting, but has no disease resistance. It grows erect, with thick, very
crinkly, glossy dark green leaves. It is good for late spring and early
summer harvest, and will often overwinter with mulching. Other Bloomsdale
types have been selected for earlier maturity and slow bolting. (48 days to
harvest)
- Melody is an All-America Selection winner (1977) that has tender,
dark green, lightly crinkled leaves with superior flavor. It has tolerance
to downy mildew races 1 and 2 and is resistant to cucumber mosaic virus. It
grows quickly to a large plant, so is good for spring or fall plantings. (42
days to harvest)
- Olympia has smooth, dark green leaves. It is very fast-growing, but
is also very slow to bolt, so is good for spring and early summer planting.
It is resistant to downy mildew races 1, 2, and 3. (46 days to harvest)
- Space is another smooth-leaved, bolt-resistant
variety suitable for later plantings. It has a thick leaf that
doesn't bruise as easily as some types, even when small. Good for both baby
spinach and full grown plants. (39 days to harvest)
- Tyee is a fast-growing savoy type with thick dark green leaves,
similar to Melody. The upright growth habit helps produce cleaner leaves. It
is very slow to bolt and is resistant to downy mildew races 1 and 3.
(39 days to harvest)
Varieties with resistance to blue mold were developed at the UW-Madison in
the late 1950's
– including Badger Savoy and Wisconsin Bloomsdale
– but these do not seem to be available anymore.
New Zealand spinach (Tetragonia expansa) is a completely different
plant in a different family. Native to New Zealand, this tender annual grows
weak, spreading stems 2-4 feet long. Its dark green leaves are smaller and
fuzzier than regular spinach, but when cooked are virtually indistinguishable
from the real thing. However, it grows best under long warm days so it will
produce all summer long when regular spinach turns bitter or goes to seed. Its
culture is the same as for regular spinach, except it should be planted 12
inches apart after the soil is warm, and the multiple seedlings from each seed
cluster should be thinned when the seedlings are large enough to handle. Pinch
off the ends of the stems of large plants to encourage new growth.
There are a number of other tropical plants that are spinach substitutes,
including Malabar spinach (Basella alba), water spinach (Ipomoea
aquatica), and Chinese or African spinach (Amaranthus gangeticus).
Planting
Plant
spinach from seed when conditions are suitable. Spinach seed does not remain
viable for very long, so purchase seed packaged for the current year. You may be
able to keep spinach seed under optimal storage conditions for a couple of
years, but germination rates will probably be much lower.
Spinach is a cool-season crop that should be planted in early spring, about 4
weeks before your area's average date of last frost. Ideal spinach weather is 50
to 60°F. Spinach does best in well-drained soil rich in organic matter, and will
tolerate partial shade. Plant seeds 1-4 inches apart and about ½ inch deep. If
you use the closer spacing, thin when the leaves touch, when the plants are
about 2" tall, using the tender leaves for salad greens.
Make sequential plantings about 2 weeks apart to continue harvesting spinach
through the summer. Choose bolt-resistant varieties for later plantings. But
even slow bolting types will not remain vegetative for very long, so each
planting's productive time will be short. Leaf quality declines when the
reproductive cycle begins with seed-stalk formation.
A fall crop often tastes better than the spring crop because the temperature
cycle of warm to cool weather is more predictable. Plant the fall crop in
mid-August for a late-September (or later) harvest. Extend the season by
covering the plants during really cold nights or grow in a cold frame. In 2001, I
made my final spinach harvest on December 22 after growing the plants in a
jury-rigged cold frame (created from a curved glass pane and board ends on my
raised bed) during the abnormally long and mild fall.
You can also try a "winter" crop, planted in late September, that
will grow a little before going dormant for the winter. Alternatively, just cut
off the leaves of the plants of your fall crop, leaving the roots and growing
point intact. These plants may overwinter to grow a new crop of leaves in the
spring. In March 2002 the plants that I had cut off in December and had been
completely unprotected during the relatively mild winter had already begun
regrowth. In colder areas or severe winters, covering the plants with mulch may
enhance their survival. Some varieties, such as Bloomsdale Longstanding, are
hardier than others, and are more likely to survive the winter.
Culture
Grow spinach in rich, moist soil with good soil aeration. Poor, dry soil only
encourages spinach to go to seed. It does best with uniformly moist soil, but try to avoid splashing water
so the leaves won't get so dirty. You can mulch around the plants to help retain
moisture and keep soil off the leaves.
Spinach is a weak competitor, so keep the spinach bed weed-free. Pull tiny
weeds or cut off larger ones at ground level to avoid injuring the shallow roots
of the spinach plants.
Spinach is a heavy feeder. Fertilize before planting and at midseason to
stimulate growth and yield. This is more important in spring when nitrogen is
less available to plants in the cold soil. Apply a sidedressing when plants are
about 2 inches tall. Use about ¼ pounds of 5-10-5 fertilizer per 10 feet of
row. If the leaves begin to yellow, add additional nitrogen.
Pest Management
There are few insects or diseases that bother spinach. Aphids may
occasionally infest plants and spinach leafminer may be problematic in some
areas. Aphids can be controlled by removing infested leaves or with chemicals if
numerous. Minor infestations are often destroyed by a variety of natural
enemies, such as green lacewings, lady beetles and parasitic wasps. Aphids may
also be washed off the leaves with a vigorous stream of water.
Spinach leafminer is a fly that lays its eggs on the undersides of the
leaves. The maggots burrow into the leaf and create conspicuous trails as they
eat their way through the leaf. Remove leaves with eggs or mines, but don't
spray chemicals since they are ineffective once the insect is inside the leaf.
To prevent leaf miner damage put floating row cover on after thinning. But use
supports, such as hoops, to keep the fabric off of the plants. unlike other
plants which tolerate row cover placed directly on the plants, the tender
spinach leaves can be abraded if the fabric brushes back and forth in windy
conditions.
Slugs can also be a problem in very moist situations. Do not mulch around the
plants.
Spinach is susceptible to rust, but most varieties are rust resistant.
Occasionally leaf spots, either Cercospora leaf spot or Anthracnose, may develop
on the upper sides of the leaves, then fall out to form holes. Fungicides will
control these diseases. Choose resistant varieties if downy mildew is a problem
in your garden.
Harvesting
You can remove individual leaves periodically starting when the plants have
at least 6 true leaves. Or harvest the entire plant at maturity. This is
probably the best harvesting method in the spring , or when a
central stalk begins to appear. Cutting the plants off at the soil line will keep the harvested leaves
cleaner than if the whole plant with its roots is
removed. In the fall, removing the outer leaves only will allow the plant to
continue to grow and produce more for continued harvest.
Wash the leaves thoroughly in plenty of water to eliminate the grit that
sometimes sticks to the leaves, especially the crinkled types.
Fresh spinach can be refrigerated up to one week. The leaves can also be
frozen, canned or dried.
Serving Suggestions
Nothing beats a salad of
tender young spinach leaves you've grown yourself
(other than maybe your own garden-fresh lettuce). There are many possibilities
for creating a unique spinach salad, such as by adding a bacon-dripping dressing
and chopped, hardboiled egg, or combining the leaves with strawberries and
walnuts lightly dressed with a raspberry vinaigrette (or orange segments, sliced
red onion and pecans).
Spinach is equally delightful cooked. Try lightly sautéing it in garlic-infused olive oil and
serve with a spritz
of Balsamic vinegar and a few pine nuts. Add chopped spinach leaves and
cannellini beans to chicken soup for a different taste. Or mix with cooked
pasta, dried tomatoes, Kalamata olives and grated Asiago cheese for a quick
dinner.
Spinach is an important ingredient in a number of traditional dishes, such as
spanakopita, the Greek spinach and feta cheese pie and many Indian dishes. It's
even added to pasta to create green noodles. In Florence, Italy, spinach was
considered a nobleman's delicacy, so today "Florentine" usually
denotes the inclusion of spinach in a recipe. There are hundreds of recipes for
Florentine dishes using fish, chicken, pasta and vegetables. One interesting
variation on the standard recipes I ran across is Blue
Cheese Mashed Potatoes Florentine.
You might want to try your homegrown spinach in some of the many recipes on
the web, such as those at:
– Susan Mahr, University of Wisconsin
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