Kohlrabi

Scientific Name: Brassica oleracea var. gongylodes

Family: Brassicaceae

Kohlrabi, a member of the cruciferous family, is a unique and nutritious vegetable that has gained popularity in recent years due to its distinctive appearance, mild flavor, and impressive health benefits. Sometimes called a "turnip cabbage" or "German turnip," this vegetable is often overlooked but is a treasure trove of nutrients and versatile in various cuisines.

Though its bulbous, round shape and leaf structure may resemble other vegetables in the Brassica family, such as cabbage, cauliflower, and broccoli, kohlrabi stands out because it’s not grown for its leaves or flowers, but rather its swollen stem, known as the "bulb." This edible part of the plant is both crunchy and mildly sweet, making it a favorite in salads, slaws, soups, and stir-fries.

In this article, we will explore kohlrabi’s history, botanical features, growing instructions, culinary uses, and health benefits, along with tips for harvesting, storing, and selecting this often-underappreciated vegetable.

History of Kohlrabi

Kohlrabi is believed to have been first cultivated in Europe around the 15th century. The name "kohlrabi" is derived from two German words: "kohl," meaning cabbage, and "rabi," meaning turnip, a reflection of its appearance. While it has been a staple in European gardens for centuries, it is also widely grown in other parts of the world, including Asia and North America.

Over the years, kohlrabi has evolved into several varieties, with the most common being green and purple cultivars. Although it is not as commonly found in traditional American gardens, its popularity has grown due to its nutritional benefits and its ability to thrive in various climates.

Botanical Description

Kohlrabi is a cool-season biennial vegetable that is grown for its swollen stem or bulb. This plant grows between 18 and 30 inches tall and has broad, slightly waxy leaves that emerge from the top of the bulb. The bulb itself can vary in color from pale green to deep purple, and it grows above the soil, unlike root vegetables.

The plant has large, fleshy, and thick leaves that grow from the top of the bulb. These leaves are edible and can be used in cooking, although the bulb is the primary edible part. The bulb is the part of the plant most commonly consumed, offering a crisp, crunchy texture and a mild flavor. The flesh of the bulb is white or pale green and can be eaten raw or cooked.

Growing Instructions

Kohlrabi is relatively easy to grow, provided the right conditions are met. It thrives in cool climates and can be grown in both spring and fall. It is best to plant it early in the season or in late summer for a fall harvest.

Sunlight: Kohlrabi requires full sunlight for at least 6 hours a day. A sunny spot in the garden will help the plant develop a firm, crunchy bulb.

Soil: Kohlrabi prefers well-draining, loamy soil that is rich in organic matter. The soil should have a pH level between 6.0 and 7.5. Adding compost or aged manure will improve soil fertility and ensure healthy plant growth.

Temperature: Kohlrabi thrives in cool temperatures, typically between 45°F to 75°F (7°C to 24°C). It can tolerate mild frosts but is best grown in spring and fall when temperatures are mild.

Watering: Kohlrabi requires consistent watering to maintain healthy growth. The soil should be kept moist, but not waterlogged. A deep watering schedule, ensuring the plant's roots are thoroughly hydrated, is ideal. Avoid over-watering, as it can lead to root rot.

Spacing: When planting kohlrabi, space the plants about 6-8 inches apart in rows that are 12-18 inches apart. This allows the bulbs to grow properly and minimizes competition for nutrients.

Pruning: Pruning is generally not necessary for kohlrabi. However, removing any damaged or yellowing leaves can improve airflow around the plant and prevent disease.

Support: Although kohlrabi does not need extra support for its bulb, providing a trellis or stakes may be helpful in windy regions to prevent damage from strong gusts.

Life Cycle: Kohlrabi typically grows as an annual, completing its life cycle within one growing season.

• Germination: Kohlrabi seeds typically germinate within 7-10 days under ideal conditions. Start seeds indoors 6-8 weeks before the last expected frost or directly sow them outdoors in early spring.

• Vegetative Growth: After germination, young kohlrabi plants develop large, thick leaves. The bulb starts to form 4-6 weeks after planting, growing above the soil surface. During vegetative growth, ensure the plants have access to sufficient nutrients and water to develop strong stems.

• Flowering: If kohlrabi is allowed to grow through the winter, it may flower in its second year. The flowers are yellow and small, and the plant will produce pods containing seeds.

• Fruit Set: In its second year, kohlrabi will produce seeds inside pods after flowering. However, most kohlrabi is harvested for its edible bulb during the first year of growth before the plant flowers and fruits.

• End of Season: Kohlrabi can be harvested once the bulb reaches a diameter of 3-6 inches, usually around 50-60 days after planting. Leaving the plant in the ground longer than necessary may result in a tough, woody bulb.

Harvesting and Foraging

Harvesting: Kohlrabi is ready to harvest once the bulb reaches 3-6 inches in diameter. It is best to harvest before the bulb becomes too large, as larger kohlrabi can become tough and woody. Use a sharp knife or garden shears to cut the bulb at the base of the plant.

Kohlrabi leaves are also edible, and they can be harvested at any point during the plant’s growth. Simply cut them off close to the stem, and use them in dishes like stir-fries or soups.

Foraging: Kohlrabi can be foraged in wild areas, but it is more commonly cultivated in gardens. Wild varieties of kohlrabi may have a tougher texture and a more bitter flavor compared to the cultivated varieties.

Plant Companions

Kohlrabi grows well alongside other cool-season vegetables like lettuce, spinach, peas, and radishes. These plants share similar growing requirements and help protect each other from pests. Avoid planting kohlrabi near tomatoes, potatoes, or strawberries, as they may compete for nutrients or attract pests.

Common Pests and Diseases

Pests:

• Cabbage Worms: These green caterpillars feed on kohlrabi leaves. Prevent them by using row covers or hand-picking pests.

• Aphids: Small green insects that can be controlled with insecticidal soap or by spraying water onto the plant.

• Flea Beetles: Tiny jumping insects that damage leaves, which can be controlled with diatomaceous earth or insecticidal soap.

Diseases:

• Downy Mildew: This fungal disease appears as yellow spots on leaves and can be controlled with fungicides.

• Clubroot: A soil-borne disease that causes swollen roots. Avoid planting in affected soils and rotate crops to prevent it.

Shopping Tips

When buying kohlrabi, look for bulbs that are firm and smooth, without cracks or blemishes. The leaves should be fresh and green. Avoid buying kohlrabi that is too large, as it can be woody and tough.

Storage

Kohlrabi, like other fresh vegetables, can spoil if not stored correctly. Signs of spoilage include wilting, mold, or a slimy texture. It's best to store kohlrabi in the refrigerator (for up to 2 weeks), in a perforated plastic bag, to maintain its freshness for up to two weeks. Remove the leaves before storing the bulb to prolong freshness. If the vegetable starts to soften or develop an off smell, it should be discarded. If you want to store it for a longer period, you can freeze kohlrabi by blanching it for a few minutes and then freezing it in an airtight container.

Food Safety

Like many raw vegetables, kohlrabi can carry harmful bacteria such as Salmonella, E. coli, or Listeria, especially if it has been improperly handled or stored. These bacteria can cause foodborne illnesses, so it's essential to:

• Wash the kohlrabi thoroughly before cutting or eating it.

• Keep the vegetable separate from raw meats and other potential contaminants during food preparation.

• Ensure that kohlrabi is stored properly in the refrigerator, ideally at temperatures below 40°F (4°C), to prevent bacterial growth.

When preparing kohlrabi (or any other produce), cross-contamination can be a concern. This happens when bacteria from raw meats, seafood, or other contaminated food items are transferred to the vegetable.

Kohlrabi, like other non-organic vegetables, may contain pesticide residues if it has been conventionally grown. To reduce exposure to pesticides, it is advisable to wash the vegetable thoroughly under running water before consumption. Choosing organic kohlrabi can also minimize this concern.

Although rare, some individuals may be allergic to certain compounds in cruciferous vegetables like kohlrabi. Symptoms of an allergy could include itching, swelling, or gastrointestinal discomfort. If you have a known sensitivity to other members of the cabbage family (e.g., broccoli, cauliflower, or Brussels sprouts), it's best to introduce kohlrabi into your diet with caution.

Culinary Uses

Kohlrabi is a versatile vegetable with a mild, slightly sweet, and peppery flavor. It can be eaten both raw and cooked, and its crisp texture makes it a popular choice for a variety of culinary applications. Here are some of the most common ways kohlrabi is used in cooking:

• Raw in Salads: Kohlrabi can be peeled and sliced or julienned to add a crunchy texture to fresh salads. Its mild flavor pairs well with other raw vegetables like carrots, cucumbers, and radishes. It can also be combined with leafy greens, avocado, and citrus for a refreshing salad.

• As a Raw Snack: Similar to raw carrots or celery, kohlrabi can be cut into sticks or wedges and enjoyed as a healthy, crunchy snack. It’s delicious on its own or paired with dips like hummus, yogurt-based dressings, or guacamole.

• Pickled or Fermented: Kohlrabi can be pickled or fermented to create tangy and flavorful sides or appetizers. Pickling enhances the vegetable’s natural crunch, and its slightly sweet taste pairs well with vinegar-based pickling brines. It’s also great for making kimchi or other fermented dishes.

• Stir-Fries: Kohlrabi can be sliced or julienned and added to stir-fries. It cooks quickly and holds its texture well, making it an ideal addition to vegetable stir-fries. Pair it with ingredients like garlic, ginger, soy sauce, and other vegetables for a savory dish.

• Roasted or Grilled: Roasting or grilling kohlrabi enhances its natural sweetness. Cut it into cubes or wedges, toss it with olive oil, salt, and pepper (and other seasonings like paprika, garlic powder, or herbs), then roast or grill it until tender and caramelized. This method brings out the vegetable’s rich, nutty flavor.

• Mashed or Pureed: Kohlrabi can be mashed or pureed, much like potatoes or cauliflower. It makes a creamy, low-carb alternative to mashed potatoes. Simply boil or steam the kohlrabi until tender, then mash with butter, cream, or olive oil, and season with salt and pepper. You can also mix it with other vegetables, like carrots or potatoes, for a more complex flavor.

• Soup or Stew: Kohlrabi can be added to soups and stews for extra flavor and texture. Its mild flavor pairs well with other root vegetables like carrots, potatoes, and parsnips, as well as with greens such as spinach or kale. You can add it to vegetable or chicken-based soups for an added crunch, or puree it to make a smooth, velvety soup.

• Kohlrabi Slaw: A variation on the classic coleslaw, kohlrabi can be shredded and combined with cabbage, carrots, and a tangy dressing to make a unique slaw. You can also add ingredients like apple, raisins, or herbs to give it a fresh twist.

• Kohlrabi Chips: Thinly slice kohlrabi and bake or fry it to make crispy chips. Toss the slices with a bit of olive oil and your favorite seasonings before baking or frying to create a healthy, crunchy snack.

• Stuffed Kohlrabi: You can hollow out the kohlrabi bulb and stuff it with a filling of your choice. Popular options include quinoa, rice, ground meat, or vegetables. After stuffing, you can bake the kohlrabi until tender and serve as a main or side dish.

• Juices and Smoothies: Kohlrabi’s mild, slightly peppery taste works well in fresh juices and smoothies. You can blend it with fruits like apples, berries, and citrus for a refreshing drink. The vegetable adds a nutrient boost to your smoothie without overpowering the other flavors.

• Kohlrabi in Casseroles: Kohlrabi can be incorporated into casseroles or gratins. Sliced thin and layered with cheese, cream, and breadcrumbs, it can replace or supplement potatoes in dishes like gratins or au gratin casseroles.

• Kohlrabi in Curries: Kohlrabi can also be added to curry dishes, especially those with a creamy coconut milk base or spiced with curry powder, turmeric, and garam masala. The vegetable absorbs the curry sauce, adding texture and flavor to the dish.

Health Benefits

Kohlrabi is low in calories but high in nutrients, including fiber, vitamin C, potassium, and antioxidants. These nutrients contribute to the following health benefits:

• Digestive Health: The fiber content in kohlrabi aids in digestion and helps prevent constipation.

• Immune System Support: High in vitamin C, kohlrabi strengthens the immune system and helps fight off infections.

• Heart Health: The potassium in kohlrabi can help regulate blood pressure, reducing the risk of heart disease.

• Anti-Inflammatory: The antioxidants in kohlrabi may help reduce inflammation in the body.

Toxicity and Safety

When it comes to kohlrabi, there are a few toxicity concerns to be aware of, although this vegetable is generally considered safe for consumption:

• Toxins in Leaves (Rare): While the kohlrabi bulb is commonly eaten, the leaves are also edible. However, there are some concerns related to consuming large amounts of certain compounds found in cruciferous vegetables, such as goitrogens, which can interfere with thyroid function if eaten in excessive quantities. Cooking or steaming the leaves can reduce the goitrogenic effect.

• Consumption of Overripe Kohlrabi: When kohlrabi is allowed to become overripe, the taste may become more bitter and its texture tougher. While overripe kohlrabi is not harmful, it can be less palatable and harder to digest. Always check for firmness and avoid using kohlrabi that has become overly soft or discolored.

Environmental Impact

Kohlrabi is considered an environmentally friendly crop. It grows well in a variety of climates and can be cultivated without heavy use of chemical fertilizers and pesticides. Additionally, kohlrabi has a relatively low water requirement compared to other crops, making it an efficient and sustainable vegetable to grow.