How Does Spinach Grow?

 

USDA Hardiness Zones: 3 - 11 Click here to view USDA Agricultural Zone map

 

Spinach is a fast growing, leafy green, flowering annual with a high tolerance for cold weather. It can survive frosts and temperatures as low as 15 degrees Fahrenheit. Spinach grows to a height of 12 inches, and because it is so fast-growing, home gardeners see quick results from their crop, yielding a harvest within as little as seven weeks after planting. 

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Seasonal Growth

 

Spinach can be grown virtually anywhere in the United States, but due to its requirements for mild weather conditions at planting, it should be started in early spring and late summer in northern climates, and in southern zones with more mild winters (USDA Hardiness Zones 7 and south), in late fall and winter. 

 

Health Benefits

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Spinach may not have quite the extraordinary levels of iron that gave Popeye the Sailor Man his super-human strength, but it is a super green that is jam-packed with nutritional benefits.

 

One serving of spinach contains the same high iron levels as a 3 oz. cut of beef. In fact, cooking raw spinach actually increases its iron content. Iron is essential for the transport of oxygen in the hemoglobin of red blood cells. 

 

When it comes to bone strengthening vitamin K, spinach is second only to kale among the green leafy vegetable family. Each cup of spinach also contains as much as 181% the daily nutritional value of vitamin K1, which helps to prevent the excessive activation of osteoclasts, cells responsible for breaking down bone. 

 

Vitamin K1 is converted to vitamin K2 in the intestines, and vitamin K2 activates osteocalcin, the major non-collagen protein in bone that anchors calcium molecules. Spinach also contains high levels of minerals such as calcium and magnesium that are essential for healthy bone support. 

 

Just one cup of spinach contains more than 50% the recommended daily value of vitamin A in the form of beta-carotene. Vitamin A is essential for eye health, aiding in the prevention of degenerative diseases such as macular degeneration. Carotenoids lutein and zeaxanthin that are present in spinach are essential for the prevention of eye-related problems.

 

Vitamin A acts as a powerful antioxidant, protecting the body from oxidative damage caused by free radicals. Free radical damage is believed to be the underlying cause of premature aging and a variety of diseases, including several forms of cancer.

 

Spinach contains more than a dozen flavonoid compounds that play important anti-inflammatory and anti-cancer roles in the body. In laboratory studies, spinach extracts have been shown to slow down cell division in human stomach and breast cancer cells, and in animal laboratory tests, skin cancer cells. Research also indicates that spinach is the only vegetable that provides significant protection against the occurrence of aggressive prostate cancer.

 

Spinach’s antioxidant properties are not limited to vitamin A. Spinach also contains high levels of vitamin C, vitamin E, manganese, zinc and selenium--all of which play a role in reducing damage from oxidative stress. 

 

Blood vessel problems such as high blood pressure and atherosclerosis are believed to be remedied by the antioxidants found in spinach. The American Heart Association suggests that people should consume foods such as spinach that are rich in vitamins C and E for the greatest health benefits instead of resorting to supplements in the form of pills.  

 

Inflammatory conditions such as rheumatoid arthritis, migraine headaches and asthma may all be helped by the nutrients found in spinach.

 

History

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Although the exact origin of spinach is unknown, the first documented reports place it in central and southwestern Asia. Common thought is that spinach originated in ancient Persia (modern day Iran) and was transported to India, China and eventually the Mediterranean by Arab traders. Following its arrival in the Mediterranean, it took spinach approximately four decades to gain popularity throughout Europe.

 

The first written record of spinach comes from Sasanian Persia circa 250 CE. In 647 CE, spinach was brought from Nepal to China, where it is known to this day as the “Persian green.” It was first documented in the Mediterranean in the 10th century, when it was referenced in two agricultural treatises by Ibn Wahshiya and Qustus al-Rumi, as well as in a medical work by al-Razi. A popular vegetable in the Arab Mediterranean, spinach eventually made its way to Spain by the end of the 12th century.

 

Italy was among the first of the young European countries to include spinach in their diets. Spinach arrived in Provence, the southeastern region of France that borders the Mediterranean sea to the south, in the 14th century. It also appeared in England around the same time, likely through trade with Spain.

 

Spinach seems to have gained popularity in England and France quickly, due to its short growth cycle with harvest time in early spring, when most other vegetables are not yet ready for picking. Spinach is mentioned in the first known English cookbook, The Forme of Cury , written in 1390 CE. 

 

In the 1870’s, the German chemist, Erich von Wolf, while researching the iron content of spinach and other green vegetables discovered that spinach contains 3.5 milligrams of iron per 100 gram serving.  However, he accidentally misplaced the decimal point in his findings, stating that spinach had 35 milligrams of iron per serving--10 times the actual amount. This incorrect calculation caused the widespread misconception that spinach is exceptionally high in iron.

 

This myth lasted well into the 20th century. In 1929, the creators of the American comic, Popeye the Sailor Man, perpetuated the story of spinach’s extraordinary iron content by feeding the cartoon protagonist canned spinach to boost his strength. It is estimated that Popeye is responsible for boosting the consumption of spinach in the United States by one-third during the 1930s. Von Wolf’s error was not found and corrected until 1937.

 

Propagation

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Spinach can be grown in a garden plot, a raised bed or a container. The plant prefers full sun, but also tolerates partial shade. For best results, spinach is planted in well-drained soil that is rich in organic matter. To encourage tender leaves, nitrogen-rich amendments such as blood meal, composted manure or time-release fertilizer are excellent additions to the soil. 

 

Spinach is a quick-growing tender crop plant that is easily propagated from seed. It should be noted, however, that although spinach seedlings may be started indoors, it is not recommended because spinach is difficult to successfully transplant.

 

Spinach seeds germinate best in soil that is approximately 60 to 65 degrees Fahrenheit, so it is important to ascertain which time of year is best to plant. For spinach seeds to germinate, soil should not be warmer than 70 degrees Fahrenheit.  In cold northern climates, spinach is planted in early spring and late summer to take advantage of mild spring and fall climates. In warm regions with mild winters, spinach is planted in late fall and through winter.

 

Harvesting

 

Because spinach does not tolerate heat well, it must be harvested before temperatures begin to soar. If the crop has not been harvested by the time the dog days of summer arrive, spinach begins to bolt (prematurely produce flowering stems) in nature’s attempt to produce seeds, and this process causes the leaves to become bitter and inedible.

 

Most varieties of spinach are ready to harvest within 45 days after planting as soon as it forms a rosette shape with five or six leaves. Mature spinach should be harvested within a week of full leaf formation, before leaves begin to turn yellow. Baby spinach leaves, which are smaller, more tender, and sweeter in flavor, may be harvested as little as 35 days after planting.

 

There are a couple options for harvesting spinach. The first is to remove the leaves individually by using scissors to cut them off at the stem. You may wish to begin on the outside of the plant, harvesting the outer, most mature leaves and working inward to the younger leaves at the center of the plant. This trim-as-needed method is referred to as the “cut and come again” method. Because spinach leaves that have been removed from the plant perish quickly, this is the best harvest method for growers who only need a small amount of spinach at a time.

 

An alternative way to harvest spinach is to cut the entire plant off at the base. This will allow the plant to resprout and perhaps yield another partial harvest during the same season. However, picking spinach will accelerate is decay rate, so it must be consumed quickly or preserved immediately after harvesting.

 

Commercial growers use mechanized harvesters to pick their crops.

 

Storage 

 

Fresh spinach may be kept in the refrigerator for 10 to 14 days. Because the excess moisture created from washing spinach may cause it to wilt, spinach should not be rinsed until it is ready for use. 

Instead, remove the yellowed or wilted leaves and wrap the spinach loosely in a paper towel to absorb moisture. Place the wrapped spinach in a plastic bag and refrigerate. Rinse prior to use. 

 

Fresh spinach will last for 7 to 10 days in the refrigerator. However, the plant loses approximately 50% of its nutritional content after seven days of refrigerator storage. For this reason, spinach should be consumed soon after it is harvested to reap its maximum nutritional benefits.

 

To prepare spinach for freezing, dip the plant in boiling water for 30 seconds or until just wilted. Remove and immediately dip in a bowl of cool water. Dry spinach with a paper towel and place in an airtight freezer bag, labeled to mark the storage date. Freezer-preserved spinach may be stored for up to two months. 

 

Fun Facts

 

China is the top world producer of spinach, followed by the United States, Japan, Turkey and Indonesia (FAOSTAT, 2011). 

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Spinach has myriad culinary uses. It is found in salads, smoothies, pasta dishes, casseroles, as a sandwich green, as a garnish, and in omelettes and other egg-based breakfast foods. 

It may be consumed raw, juiced, cooked or canned.

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How to grow spinach in your home garden:

 

1. To start spinach from seed, choose a sunny location with well-tilled soil. You may wish to add compost, manure or a store bought organic fertilizer prior to planting, as spinach thrives in nitrogen-rich, well drained soil. 

1. Plant spinach seeds about  ½” deep, spaced approximately 2” to 3” apart in rows, or in a scattered configuration with approximately 12 seeds per square foot. For baby spinach, space seeds 1” to  2”  apart. 

2. Tamp down the soil over the seeds, and provide ample water during germination.

3. Mulch may be applied to retain moisture. When seedlings sprout to approximately 4” in height, thin them to stand 4” to 6” apart, but beyond this, no further cultivation is necessary, as spinach roots are shallow and easily damaged. The culled plants may be kept for culinary use as baby spinach. 

4. Spinach will be ready to harvest in as little as 45 days after planting. 

 

In cold climates, protect spinach through the winter with thick mulch or with a cold frame. Protection may be removed when soil temperature in your area reaches 40 degrees Fahrenheit.

 

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