Scientists now agree that cartoonist E.C. Segar chose spinach as Popeye’s secret weapon not because it was high in iron—as most of us thought—but because it was high in vitamin A. To be fair, spinach is higher in iron than most vegetables, although plant-based iron is not well absorbed by the body.
Our favorite sailor’s bulging biceps are probably better attributed to spinach’s substantial amounts of vitamins A, C, K, E, B2 (riboflavin), B6, and B9 (folate) as well as minerals such as magnesium, calcium, and potassium.
While I’m delighted that spinach is a superfood, I cultivate it mainly for the delicious ways it can be enjoyed in salads, quiches, soups, and dips—not for building mega muscles. And it’s easy to grow in my garden.
Spinach (Spinacia oleracea) is an annual vegetable that likes cool weather and plentiful moisture. There are three types of spinach—all taste much alike and can be eaten raw or cooked.
Savoy spinach has crisp, thick, dark green, crinkled leaves that are especially cold-resistant; they are more difficult to clean but hold up better when cooked.
Flat-leaf spinach has smooth, medium-green leaves that are easier to wash; it’s the type most used for baby-leaf crops (leaves harvested when still small).
Semi-savoy spinach is a good compromise, with leaves that are less crinkled than savoy, and less smooth than flat-leaf.
Not all spinach seeds are alike either. Round seeds typically produce flat-leaf varieties, prickly seeds savoys, but the rule isn’t hard and fast. Botanists like to point out that neither type is technically a seed but is a tiny, one-seeded fruit, or utricle, encased in a hard capsule.
Getting Started – Sow seeds directly in the garden in very early spring for spring to early summer harvest; in late summer or early fall for fall and early winter harvest.
Spacing – Plant seeds half-inch deep, two inches apart, thinning six to 10 inches apart. Space rows about 12 inches apart.
Days to Maturity – Harvest in 23 to 50 days, depending on variety and leaf maturity.
Spinach growing guidelines
Spinach plants are both heat- and light-sensitive. Temperatures above 75 degrees Fahrenheit (F) and days longer than 14 hours cause plants to bolt—to send up flower stalks, making them inedible—so success comes in the cooler, shorter days of spring and fall.
Even slow-bolting cultivars such as ‘Olympia’ and ‘Corvair’ won’t thrive in summer’s heat. Or, as one of my local farmers put it, “Spinach ain’t beans.” In addition to short, cool days, spinach needs full sun and light, moist soil that is organically rich, drains well, and is neutral to slightly alkaline (pH 6.5 to 7.5).
Growing spinach in most regions is pretty straightforward: Direct-sow seeds as soon as the soil can be worked for spring/early summer harvests and about six weeks before the first hard frost for fall/early winter harvests.
To get a head start on spring crops, sow seeds about four weeks before the first frost in the fall, then overwinter the seedlings by covering them with a foot of straw secured by a heavy floating row cover (rated AG-50 or more).
Remove the row cover and straw when warmer weather resumes in spring. Set seeds a half-inch deep, two inches apart, then thin to six to 10 inches once the seedlings are three to four inches tall.
Overcrowding curbs growth and encourages bolting. Spinach also grows well in window boxes and pots.
Use containers that are at least eight inches deep and give plants plenty of room.
Seeds will sprout in near-freezing soil, but 55 to 68 degrees F is optimal. Germination rates plummet when the soil temperature tops 70.
Most resources claim spinach is difficult to transplant, but that hasn’t been my experience. Spring-sown seeds rot in the soppy clay soil of my garden, so I start them in individual pots on the deck. Because the pots are outdoors, the seedlings don’t need to be acclimated before I transplant them. Gardeners with summers hotter than you-know-what may need to begin fall crops indoors, then give plants some shade outdoors before setting them out in the vegetable bed.
As vegetables go, spinach matures in a New York minute. Most varieties are ready to pick as a baby-leaf in 25 days and fully mature in 40 to 45 days. To have a continuous supply, I replant every 10 days until the weather is either too hot or too cold.
Spinach is a heavy feeder, but garden soil rich with organic matter normally contains all the nutrients it needs. If you’re growing it in containers or if plants aren’t thriving, side-dress once or twice during the growing season with diluted fish emulsion to provide an extra shot of nitrogen.
Make sure to provide constant moisture—spinach is 92 percent water—and mulch to discourage weeds, cool the soil, and retain moisture for the shallow feeder roots.
Pests and diseases
Few pests—not counting rabbits—bother spinach, but downy mildew, a fungal disease, sometimes plagues plants, especially those spaced too closely or subject to prolonged periods of rain.
The leaves of affected plants have a bluish-white or gray fuzz on their undersides or yellow spots on the topsides. You can treat the diseased plants with a fungicide, or you can just pull and discard them.
Most of today’s cultivars have at least some built-in disease resistance. To discourage soil-borne diseases such as fusarium, plant spinach in a different spot each year. Aphids, which can spread viruses, can be washed off with a strong spray of water.
In 2018, I had the best results with two hybrid semi-savoys, both new to me: slow-to-bolt ‘Indian Summer’ and downy-mildew-resistant ‘Carmel.’ ‘Space’ is a superb smooth-leaf cultivar that is also highly resistant to downy mildew. I still like the open-pollinated heirloom savoy ‘Bloomsdale Long Standing,’ which has no disease resistance but does have great flavor. All of the above mature in 35 to 45 days but can be harvested earlier as baby spinach.
Smaller varieties that are good choices for containers include ‘Baby’s Leaf,’ which matures in 30 to 40 days, and ‘America,’ which matures in about 50 days. ‘Red Kitten,’ a red-stemmed spinach, is especially pretty but bolts quickly, so it is best grown as a baby-leaf; it can be harvested in as little as 23 to 34 days.
While ‘Winter Bloomsdale,’ ‘Samish,’ and ‘Giant Winter’ can mature in about 45 days, these cold-hardy varieties are particularly good choices for fall plantings that are covered over winter to provide a very early harvest in spring. Spinach seeds don’t store well—germination rates drop significantly in a year or two—which gives you a good excuse to try new cultivars every year.
Spinach substitutes for warm climates
During hot weather, spinach lovers can try these heat-tolerant substitutes: Malabar spinach (Basella alba) and New Zealand spinach (Tetragonia tetragonioides). Their flavors and textures are similar to those of spinach.
Malabar is a vining tropical that requires a trellis; it loves heat, full sun, and slightly acidic, fertile soil.
New Zealand spinach has a spreading habit, rambling two feet or more. It likes moderate conditions, organically rich soil, a neutral pH, and plenty of water.
Both plants are perennial in frost-free regions but are usually grown as annual.
Enjoying the harvest
Plants produce edible leaves for about a month. Begin harvesting as soon as the leaves are large enough to use, either by picking individually or by cutting the whole plant. If you leave two inches of growth above the crown, the plant may resprout.
Spinach, especially savoy spinach, requires several washings to remove all the grit that collects in the leaves. Store unwashed or use a salad spinner or paper towels to remove excess water from washed spinach before packing loosely in a sealed plastic bag and refrigerating. Storage life is about five days.
Since spinach won’t stay fresh for long in the refrigerator, you’ll probably want to preserve your harvest for times when fresh spinach isn’t available. The good news is that there are various ways to preserve spinach, and some of these food preservation methods are quite familiar to many of our readers.
Blanching and freezing
This is the most commonly used method for spinach preservation, and it helps you enjoy your harvest and its deliciousness all year long. Some people prefer to just wash, chop and freeze the spinach, but if you want it to retain all its nutrients, it’s better to avoid skipping the blanching step.
Tip: When cooking with frozen spinach, you should avoid thawing it as it will lose a great deal of its vitamin C content. Use the frozen spinach directly in the recipe and pay attention to how its amount of water content may affect your recipe.
This method of preservation is not so common because spinach loses its flavor when it dries. However, dry/dehydrated spinach maintains its nutrient value, and it can be added to many recipes. To sneak it into recipes for your kids, you can ground the dried leaves into powder and use it as needed.
Canning spinach also works, but it takes a decent amount to get any jars. You will need four pounds of spinach to make one single quart. Also, it doesn’t smell the greatest while canning. Since it’s a low-acid food, it has to be pressure canned. The canned spinach can be warmed up and eaten, or you can drain it and add it to just about any dish you want.
As for the foremost spinach question—“How do I get my kids to eat it?”—take a look at the bonanza of spinach dessert recipes online. If you can’t unload Chocolate Spinach Brownies with Peanut Frosting or spinach ice cream, which is delightfully green, I’d give up. Plant sweet corn, instead.
Useful resources to check out: