Celebrate the Year of the Brassica

According to the National Garden Bureau, 2017 is the Year of the Brassica. This large family of nutritionally rich vegetables includes broccoli, cabbage, cauliflower, kale, kohlrabi, radishes and more. These cool-season vegetables are best planted in early spring.

Broccoli

Start broccoli seeds indoors six weeks before the last frost. When seedlings are four weeks old, plant them outside in full sun and in well-drained soil rich with organic matter. Give plants abundant amounts of nitrogen and calcium.

Space plants 18 inches apart in the garden, a little closer in containers. Harvest broccoli when the florets are just beginning to open. Keep watering and most varieties will produce side shoots with smaller heads.

Cabbage

There are cabbage varieties in white, green, blue, red and purple. Like broccoli, they require heavily amended, well-drained soil. Fertilize with fish emulsion when they begin developing leaves and again when heads start forming. A balanced, slow-release fertilizer can also be worked into the soil before planting.

Set small transplants in the garden or containers a few weeks before the last frost. Space them from 12 to 24 inches apart depending on the variety. The secret to growing cabbages is to provide steady care. Stressed plants may not recover.

Cauliflower

We are all familiar with white cauliflower. This year, try purple and orange varieties for fun. Cauliflower grows best in consistently cool temperatures. Heat stress can cause premature heading.

A few weeks before the last frost date, space transplants about 18 inches apart in the garden, closer in containers. Have some sheets available to cover plants if frost is expected.

Choose a location with full sun and prepare the garden before planting. Mix blood meal, cottonseed meal or composted manure in moist, well-drained soil. Cauliflower is sensitive to both over and under watering.

When cauliflower heads are beginning to form, secure leaves over each head to keep them white and tender. Some varieties are self-blanching, but lend a hand if the leaves aren't doing their job.

Harvest heads when they are 6 inches in diameter. Continue watering plants and most will grow more, smaller florets.

Kale

Kale is one of the most nutrient-dense foods. There are curly- and smooth-leaf varieties in green, blue-green and purple.

Sow seeds directly in the garden two to four weeks before the last frost date or start them inside up to eight weeks before the last frost date. Transplant them outside as early as a month before the last frost. Cover plants in frosty weather.

Kale grows best in full sun, but will produce satisfactorily in part shade, too. Space transplants 18 to 24 inches apart. The most tender leaves are produced in fertile, consistently moist soil.

Kohlrabi

Sow seeds in the sunny garden a few weeks before the last frost date in amendment-rich, well-drained soil. Fertilize with a balanced, slow-release fertilizer when planting and feed again when plants begin to form heads. As seedlings emerge, thin them to at least 6 inches apart - more if they are seeds of a giant variety. Transplants can be started indoors for a super early crop.

Keep plants evenly moist for the best and fastest growth. Even moisture keeps their centers from getting pithy. It has been the rule to harvest them while still small, but now varieties that produce giant heads stay delicious all the way to their centers as they grow nearly as large as a softball.

Radishes

Planting radish seeds is a great garden project with children. They germinate quickly, perfect for impatient gardeners. They are ready to eat just a few weeks after sowing.

Plant seeds an inch apart directly in light, well-drained soil four to six weeks before the last frost date. Thin seedlings so they grow 2 to 3 inches apart. Make small successive plantings every week or so for a steady supply until the temperatures warm.

Soggy soil causes radishes to split. Harvest them as soon as they are ready to add color and crunch to salads, or just pop them in your mouth as a snack.

The most difficult part of growing radishes may be selecting which variety to grow. There are varieties in many shapes - cute little round ones and others that reach as deep as 18 inches long - and colors from white to bright red and rose to purple.

• Diana Stoll is a horticulturist, garden writer and the garden center manager at The Planter's Palette in Winfield. She blogs regularly gardenwithdiana.com.