Keen on Kale

Colorado State Univ. Field DayIt used to be relegated to garnish status, if you could find it at all. Kale’s strong flavor placed it in last place when compared to its more appealing relatives such as cabbage, cauliflower, and broccoli. Even the oft-hated Brussels sprouts were more popular. But now, kale is finally getting the accolades it deserves. From kale smoothies to the seared kale I enjoyed at a restaurant recently, its showing up everywhere. With its abundant nutrients and new, milder flavor, kale might be the “trendy veggie” of the decade.

All the “cole crops”—those mentioned above, along with kohlrabi  and collards, are considered the same species, Brassica oleracea, and have just been bred for different traits. If we compare a head of cabbage to a head of iceberg lettuce, then kale is the leafy equivalent. And just as leaf lettuce has a higher nutrient content than iceberg, so kale offers more vitamins and minerals than head cabbage. Kale’s popularity has soared along with our renewed desire to “eat healthy.”

Most markets now offer bundles of large kale leaves, secured with a wire twist-tie. These mature leaves tend to be a bit wilted after traveling all the way from the field, and there’s usually only one variety to choose from—the grayish blue-green, ruffled type. If you’re like me, and happen to prefer your greens fresh, crisp, and still small and tender, you aren’t going to be satisfied at the store. Happily kale is very easy to grow at home, even without a dedicated vegetable garden.

kale_dbg_20090915_lah_0504The first task is to decide which type of kale to grow. There are over a hundred varieties, ranging from Black Magic to White Peacock. Leaves can be frilly or plain, ruffled, savoyed, long and thin or short and wide. And as their names suggest, some are black, others are light silvery green, and still others (such as the heirloom Red Russian) glow a luscious purple-red. Taste tests praise Red or Black Russian, so you might want to start there, and then grow another variety or two for comparison.

Ornamental, or flowering, kale isn’t the only kale that is pretty as well as edible. Add an exotic note to your landscape by mixing plants into your shrub borders or flower beds, or include them in containers of flowers on your deck or patio.

When it comes to cultivation, the experts agree that rich soil is a must. Plants in the cabbage family store food in the first leaves to form, then draw on that cache later in the season. Therefore, it’s important to plant them in fertile soil to start with. Later side-dressing won’t help. Additionally, these plants have a relatively small, shallow, and inefficient root system, and you want quick growth for tender, mild-flavored leaves. A soil test will help you ensure fertility without going too far and adding too much fertilizer or compost.

Brassicas are also very sensitive to underwatering. Wilting will permanently stunt their growth, so it is essential that the plants never dry out. A three to four inch layer of mulch will help maintain a constant soil moisture level while suppressing weeds.

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You can direct seed the plants in the garden or start them earlier indoors. Kale seedlings are fairly hardy and will survive some late spring frosts, but several days of exposure to temperatures under 40 will cause the plants to bolt before you get a chance to harvest. For that reason, I prefer to wait until the weather is warm and settled. Besides, while kale can be picked all summer, it tastes best after the first frosts of fall sweeten the leaves.

Mature plants can withstand temperatures as low as zero, so you can continue to harvest the leaves until winter. You can even try overwintering plants under loose mulch or row covers for a very early spring harvest. They’ll bolt as soon as the weather warms, however, so be sure to plant a new crop, too.

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Cabbage looper, photo by Whitney Cranshaw, Bugwood.org

The most common problem with kale is the array of cabbage-eating caterpillars. You first notice holes in the leaves. On closer inspection, you see the frass (brown caterpillar poop), and finally, the hungry green critters themselves. There are several ways to control these ravenous beasts. Row covers prevent the white cabbage butterflies from laying eggs on the leaves. You can spray with Bacillus thuringiensis (Bt), a soil-dwelling bacteria that specifically kills caterpillars. Dipel is one popular brand. Or you can take out your frustrations and hand-pick them. If the caterpillars are a constant problem, try growing red kale, which they are more likely to avoid.

Other common insect pests include flea beetles and aphids. I’ve written about flea beetles in a previous post (see Tiny Black, Jumping Leaf-chompers). Aphids are somewhat easier to deal with—you can wash them off with a strong jet of water or spray insecticidal soap (or both).

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