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Growing Kohlrabi – Doctor Intelligence (Diseases) for Iowa: Complete Guide & Best Practices
Kohlrabi is a unique and versatile vegetable that is well-suited for growing in the Midwest region of the United States, including the state of Iowa. This member of the Brassica family is known for its distinctive bulbous stem that grows above the ground, which can be eaten raw, roasted, or incorporated into a variety of dishes.
While kohlrabi is a relatively easy crop to cultivate, it is important to be aware of the potential diseases and pests that can affect its growth and productivity. In this comprehensive guide, we will explore the best practices for growing kohlrabi in Iowa, with a particular focus on identifying and managing common diseases that may impact your harvest.
Choosing the Right Variety for Iowa
When it comes to growing kohlrabi in Iowa, the selection of the right variety is crucial. Some of the most well-suited varieties for the state’s climate and growing conditions include:
- Early White Vienna: A fast-maturing variety that is known for its tender, mild-flavored bulbs.
- Purple Vienna: A beautiful cultivar with a distinctive purple-tinged skin and a crisp, juicy interior.
- Kossak: A large, globe-shaped variety that is ideal for storing and can withstand the fluctuating temperatures of the Midwest.
It’s important to choose a variety that is well-suited to your specific growing conditions, such as the length of your growing season, the average temperatures in your area, and the soil type. Consulting with local agricultural extension offices or experienced gardeners can help you make the best selection for your needs.
Planting and Caring for Kohlrabi
Kohlrabi can be grown from seed or transplanted as seedlings, and it prefers well-drained, nutrient-rich soil with a pH between 6.0 and 7.0. In Iowa, the optimal planting time is typically in the spring, with a second crop planted in the late summer for a fall harvest.
When planting, be sure to space the seeds or seedlings about 6-8 inches apart, with rows spaced 12-18 inches apart. Kohlrabi grows best in full sun, so be sure to choose a location that receives at least 6-8 hours of direct sunlight per day.
Throughout the growing season, be sure to keep the soil consistently moist but not waterlogged. Regular weeding and mulching can also help to retain moisture and suppress weed growth. Fertilize your kohlrabi plants every 4-6 weeks with a balanced, water-soluble fertilizer to ensure they receive the necessary nutrients for optimal growth.
Identifying and Managing Common Diseases in Iowa
While kohlrabi is generally a hardy and disease-resistant crop, there are a few common diseases that gardeners in Iowa should be aware of. By recognizing the symptoms and taking proactive measures, you can protect your kohlrabi plants and ensure a bountiful harvest.
Clubroot
Clubroot is a soil-borne disease caused by the pathogen Plasmodiophora brassicae. It affects the roots of kohlrabi and other Brassica crops, causing them to become swollen and distorted, which can lead to stunted growth and decreased yields.
Symptoms of clubroot include:
- Swollen, club-shaped roots
- Wilting and yellowing of leaves
- Stunted plant growth
To manage clubroot, it’s important to maintain proper soil pH levels (between 6.5 and 7.0) and to practice crop rotation, avoiding planting Brassica crops in the same location for at least 3-4 years. You can also use resistant varieties and apply lime to the soil to increase the pH.
Black Rot
Black rot is a bacterial disease caused by the pathogen Xanthomonas campestris pv. campestris. It can affect the leaves, stems, and even the kohlrabi bulb, causing discoloration, wilting, and ultimately, plant death.
Symptoms of black rot include:
- V-shaped, yellow lesions on the leaves that progress to a black, necrotic appearance
- Blackening and rotting of the kohlrabi bulb
- Stunted plant growth
To manage black rot, be sure to practice good sanitation by removing and disposing of any infected plant material. Avoid working in the garden when the plants are wet, as this can spread the bacteria. You can also apply a copper-based fungicide to help prevent the spread of the disease.
Alternaria Leaf Spot
Alternaria leaf spot is a fungal disease that can affect the leaves of kohlrabi plants, causing distinctive circular, brown lesions with concentric rings.
Symptoms of Alternaria leaf spot include:
- Brown, circular lesions with concentric rings on the leaves
- Premature leaf drop
- Decreased plant vigor and productivity
To manage Alternaria leaf spot, be sure to practice proper spacing and air circulation around your plants to reduce humidity levels. You can also apply a fungicide containing copper or Bacillus subtilis to help prevent the disease from spreading.
Downy Mildew
Downy mildew is a fungal disease that affects the leaves of kohlrabi plants, causing them to develop a gray, fuzzy growth on the underside of the leaves.
Symptoms of downy mildew include:
- Gray, fuzzy growth on the underside of the leaves
- Yellowing and wilting of the leaves
- Decreased plant vigor and productivity
To manage downy mildew, be sure to provide good air circulation around your plants and avoid overhead watering, as this can create the moist conditions that the fungus thrives in. You can also apply a fungicide containing copper or Bacillus subtilis to help prevent the spread of the disease.
Harvesting and Storing Kohlrabi
Kohlrabi is typically ready for harvest when the bulbs are 2-4 inches in diameter, usually 50-60 days after planting. To harvest, simply twist and pull the bulbs from the ground, being careful not to damage the stems or leaves.
Once harvested, you can enjoy your kohlrabi raw, roasted, or incorporated into a variety of dishes. To store, simply trim the leaves and stems, and place the bulbs in a plastic bag or airtight container in the refrigerator. Properly stored, kohlrabi can last for up to 2-3 weeks.
Conclusion
Growing kohlrabi in Iowa can be a rewarding and delicious experience, but it’s important to be aware of the potential diseases that can impact your crop. By choosing the right variety, following best practices for planting and care, and being vigilant in monitoring and managing common diseases, you can enjoy a bountiful harvest of this unique and versatile vegetable.
Remember, the key to success in growing kohlrabi in Iowa is to stay informed, be proactive, and adapt your strategies to the unique growing conditions in your area. With a little bit of care and attention, you can enjoy the crisp, refreshing flavor of homegrown kohlrabi all season long.
