Rapini/Broccoli Raab

Brassica rapa

Brassica rapa var rapa

by Sonoma County Master Gardener Sandy Main

Rapini or Broccoli Raab (also spelled Rabe; pronounced “rob”) is a green cruciferous vegetable. This vegetable resembles small heads of broccoli and is associated, particularly, with Italian, Galician and Portuguese cuisines. Small edible yellow flowers may be blooming among the buds. The flavor of rapini has been described as nutty, bitter and pungent. Even though it has a slightly bitter taste, it is delicious and very easy to grow.

Rapini is a member of the Brassicaceae (mustard) family and is in the same subspecies as the turnip: Brassica rapa var rapa. The cultivated vegetable probably descends from a wild herb related to the turnip that grew either in China or the Mediterranean region. Rapini is similar in shape to the Chinese Brassica oleracea cultivar called kai-lan. Rapini is now grown throughout the world and is available all year long. The peak season in Sonoma County is fall to spring.

Rapini has the same growing season as broccoli, which means planting them to mature during cool weather. In milder climates of the county, plant in late summer, fall or winter for crops in winter or early spring. In colder-weather microclimates, set out young plants two to four weeks before last frost. Young, but established, plants resist frost, but not hard freezes. A plastic tunnel or frost blanket may be used to protect plants when cold weather is predicted.

Two cultivars to consider:

- ‘Zamboni’ (my favorite) matures in 45 to 70 days and produces clusters of large buds on tall, erect, blue-green, uniform plants with small delicate leaves.
- ‘Spring Raab’ matures in 40 to 45 days. It is fast-growing, producing numerous turnip-like leaves and is especially good for spring sowing (hence, the name). This cultivar is more bolt-resistant.

Seedlings are ready to plant four to six weeks after sowing indoors, and two to four weeks before the average date of last frost – generally, mid-November in Sonoma County. Start harvesting 40 to 100 days later. As the spring-planted Rapini deteriorates, plant tomato plants among the Brassicas, letting the two crops share space for a while. Rapini are cool-season plants that bolt into flower at high temperatures. Once they start to flower, harvest them while still succulent; the flavor will not improve after it bolts. Or, allow a few to flower to attract beneficials as you transition your garden to warm-season crops.

Rapini does not require heavy fertilization, but does appreciate a bit of a nutritional boost such as a side-dressing of good-quality compost during the growing season. It prefers soil with a pH above 6.0. For the home gardener, plant or thin to six-inches apart, so that plants can develop a good quantity of greens. Pulled seedlings transplant well and can be moved to another row, if desired.

This crop, along with other Brassicas, should be rotated (planted in different areas each year or two) because diseases and insect pests of the Brassica family will build up. There are a few common problems for Rapini:

In the early fall, aphids can cause deformed, curled leaves with colonies of gray-green insects on leaves along with sticky honeydew. Use insecticidal soap spray and control ants with a sticky barrier. Encourage beneficials.  

Another possible problem is the diamondback moth caterpillar. These are evidenced by small holes in the leaves, chewed growing points in young plants and loose cocoons about one-third-inch long on leaves. The use of Bacillus thuringiensis is very effective. Older plants will not be damaged. Destroy weeds in the mustard family that can harbor these pests before planting rapini.

Improper watering causes heads to suddenly split. Do not allow soil to get too dry. If it does get too dry, apply water slowly at first.

 

Harvest plants before buds open, at a height of 10 to 15 inches. Cut the plants at the

ground level, or where the stem tissue ceases to be tough and becomes succulent. If you harvest carefully, leaving two leaves intact, they will often re-sprout several times.

After harvesting, store unwashed rapini in a plastic bag in the refrigerator for up to five days. The vegetable can also be blanched and frozen for later use. The young leaves of these plants are used in cooking either the same as turnip tops or turnip greens. Rapini is a good source of vitamins A, C and K, as well as potassium, calcium and iron.