Kohlrabi, scientifically known as Brassica oleracea var. gongylodes, is a unique vegetable that belongs to the cabbage family. It is characterized by its bulbous stem, which is often consumed as a vegetable. Kohlrabi is rich in nutrients, including vitamin C, potassium, and fiber, making it a nutritious addition to any diet. In this guide, we will explore the step-by-step process of growing kohlrabi successfully. From selecting the right variety to harvesting the mature bulbs, you will find all the essential information needed to cultivate this versatile and delicious vegetable.
What is Kohlrabi?
Kohlrabi is a vegetable that belongs to the Brassica family and is grown for its edible bulbous stem. It has a mild, slightly sweet flavor that is reminiscent of cabbage and turnips. The bulb of kohlrabi can come in different colors, including pale green, purple, or white. It is typically harvested and consumed when it reaches its optimal size, around 2-3 inches in diameter.
Nutritional Value of Kohlrabi
Kohlrabi is not only delicious but also packed with essential nutrients. It is a rich source of vitamin C, providing a significant portion of the recommended daily intake. Additionally, it contains dietary fiber, potassium, and various other vitamins and minerals. Kohlrabi is also low in calories, making it a great choice for those looking to maintain a healthy diet.
There are several varieties of kohlrabi available, each with its unique characteristics. Some popular varieties include:
Early White Vienna:
This variety produces small, pale green bulbs with a tender texture.
Early Purple Vienna:
As the name suggests, this variety produces purple-colored bulbs. It has a slightly sweeter flavor than the white variety.
This variety is known for its large-sized bulbs, which can reach up to 10 inches in diameter. It has a milder taste compared to other varieties.
Preparing for Kohlrabi Cultivation
Climate and Soil Requirements
Kohlrabi is a cool-season vegetable that thrives in moderate temperatures. It prefers temperatures between 40°F and 75°F (4°C to 24°C). It can tolerate light frosts but does not do well in extreme heat.
When it comes to soil, kohlrabi prefers well-drained soil with a pH level between 6.0 and 7.5. Before planting, it is advisable to prepare the soil by adding organic matter such as compost to improve its fertility and drainage.
Seed Selection and Sowing
Selecting high-quality kohlrabi seeds is essential for successful cultivation. Look for reputable seed suppliers or nurseries that offer reliable seed varieties. Check the seed packets for the recommended sowing dates and any specific instructions provided by the supplier.
Seed Starting Indoors
If you live in an area with a short growing season, starting kohlrabi seeds indoors can give your plants a head start. Approximately 4-6 weeks before the last expected frost date, sow the seeds in seed trays or small pots filled with seed-starting mix. Plant the seeds about ¼ to ½ inch deep and keep the soil consistently moist.
Provide sufficient light to the seedlings by placing them near a south-facing window or using artificial grow lights. Maintain a temperature of around 70°F (21°C) for optimal germination. Once the seedlings have developed their second set of true leaves, they are ready for transplanting.
Direct Sowing in the Garden
If your climate allows, kohlrabi seeds can be directly sown in the garden. Wait until the soil temperature reaches around 40°F (4°C) for proper germination. Prepare the soil by removing any weeds and debris, and create furrows that are ½ inch deep. Space the seeds 1-2 inches apart and cover them with soil. Water gently to keep the soil moist until germination occurs.
Growing Kohlrabi Seedlings
When the kohlrabi seedlings have grown their second set of true leaves and are approximately 3-4 inches tall, they are ready for transplanting. Choose a location in your garden that receives full sunlight or partial shade.
Space the seedlings about 8-12 inches apart to provide enough room for their bulbous stems to develop fully. Gently remove the seedlings from their containers, being careful not to damage their delicate roots. Dig holes in the garden soil and place the seedlings, covering their roots with soil. Water thoroughly after transplanting to ensure good establishment.
Providing Optimal Growing Conditions
Kohlrabi plants thrive in well-drained soil that is kept consistently moist. Watering deeply but infrequently is recommended to encourage the development of a strong root system. Aim to provide the plants with about 1 inch of water per week, either through rainfall or supplemental irrigation.
To promote healthy growth, it is important to provide adequate nutrients. Fertilize the kohlrabi plants with a balanced organic fertilizer or a slow-release granular fertilizer according to the package instructions. Apply the fertilizer around the base of the plants, taking care not to allow it to come into direct contact with the stems or leaves.
Watering and Fertilizing
Watering and fertilizing are essential aspects of kohlrabi plant care. Keep the soil consistently moist, especially during hot and dry periods. Water deeply, ensuring that the moisture reaches the root zone. Mulching around the plants can help retain soil moisture and suppress weed growth.
Fertilize the kohlrabi plants every 3-4 weeks with a balanced vegetable fertilizer. Follow the instructions provided on the fertilizer packaging for proper application rates. Avoid over-fertilizing, as this can lead to excessive foliage growth at the expense of bulb development.
Caring for Kohlrabi Plants
Mulching and Weed Control
Mulching is beneficial for kohlrabi plants as it helps to retain soil moisture, suppress weed growth, and maintain even soil temperatures. Apply a layer of organic mulch, such as straw or shredded leaves, around the base of the plants. Ensure that the mulch does not come into direct contact with the stems to prevent rotting.
Regular weeding is crucial to keep the kohlrabi plants healthy and free from competition for nutrients and water. Remove weeds by hand or use a hoe, being careful not to disturb the shallow root system of the plants. Weed early and frequently to prevent weed seeds from establishing and causing problems later on.
Pests and Diseases
Kohlrabi plants are susceptible to certain pests and diseases that can affect their growth and productivity. Common pests include cabbage worms, aphids, flea beetles, and cabbage loopers. Monitor your plants regularly and take appropriate action if you notice any signs of pest infestation.
To control pests, you can use organic insecticides or practice natural pest control methods, such as handpicking insects or using insecticidal soap sprays. Introducing beneficial insects, like ladybugs and lacewings, can also help keep pest populations in check.
Common diseases that affect kohlrabi include clubroot, powdery mildew, and black rot. To minimize the risk of disease, practice crop rotation, maintain good airflow around the plants, and avoid overhead watering. If necessary, use fungicides labeled for use on kohlrabi, following the instructions carefully.
Companion Planting with Kohlrabi
Companion planting involves growing compatible plants together to maximize their growth and health while deterring pests and enhancing pollination. Some suitable companions for kohlrabi include herbs like dill and mint, as well as other members of the cabbage family, such as kale and Brussels sprouts.
Avoid planting kohlrabi near strawberries, tomatoes, or pole beans, as these plants can negatively affect kohlrabi growth or attract similar pests.
Harvesting and Storing Kohlrabi
Kohlrabi bulbs are typically ready for harvest when they reach a size of 2-3 inches in diameter. The bulbs should feel firm and solid when gently squeezed. If they become too large, they may become woody and lose their tenderness.
Harvesting Kohlrabi Bulbs
To harvest kohlrabi bulbs, use a sharp knife or garden shears to cut the stems just above ground level. Remove any leaves attached to the stems. If there are any small secondary bulbs, you can harvest them as well, although they may be less tender than the main bulbs.
Proper Storage Techniques
Freshly harvested kohlrabi bulbs can be stored in the refrigerator for up to two weeks. Remove the leaves, wash the bulbs, and place them in a perforated plastic bag or a container with high humidity. This will help retain their moisture and crispness.
Kohlrabi Recipe Ideas
Kohlrabi is a versatile vegetable that can be enjoyed raw or cooked. One popular way to enjoy it is by making a kohlrabi slaw. Peel the kohlrabi bulbs and shred them using a grater or a food processor. Add shredded carrots, cabbage, and your favorite dressing to create a refreshing and nutritious slaw.
Roasting kohlrabi enhances its natural sweetness and creates a delicious side dish. Cut the kohlrabi bulbs into cubes or wedges and toss them with olive oil, salt, and pepper. Spread them on a baking sheet and roast in a preheated oven at 400°F (200°C) for about 25-30 minutes, or until they become tender and slightly caramelized.
Kohlrabi can also be used to make a creamy and flavorful soup. Peel and chop the kohlrabi bulbs, along with other vegetables like onions, carrots, and celery. Sauté them in a pot with butter until they soften. Add vegetable broth, herbs, and spices, then simmer until the vegetables are tender. Blend the mixture until smooth, and season with salt and pepper to taste.
Growing kohlrabi can be a rewarding experience, providing you with a fresh and nutritious vegetable for your meals. By following the step-by-step guidelines in this guide, from seed selection to harvesting, you can cultivate healthy kohlrabi plants with ease. Experiment with different varieties and recipes to fully enjoy the unique flavors and versatility of kohlrabi. Happy gardening and bon appétit.