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Mustard Seeds, Unzen Kobu
Description
(Brassica juncea var. integrifolia). A unique regional delicacy in Japan, this mustard green has a “knotted,” bumpy base and sweet flavor with just enough pungency to make your nose tingle. Known as the only type of takana mustard that can be eaten raw, this easy-to-grow brassica has been recognized by the prestigious Slow Foods Foundation, thanks to its rich history and phenomenal flavor. Originally developed by a small farmer and seed store owner in Unzen, the variety almost disappeared in the 1960s. Luckily, in the early 2000s this regional treasure was unearthed and shared by Iwasaki Masatoshi, and is currently being safeguarded by a group of local farmers.
- 45 days to maturity
- 6-12 hours of sun
- Sprouts in 5-8 days
- Seed Depth: 1/4”
- Plant Spacing: 12"
- Ideal Temperature: 50-80 F
- Frost Hardy: Yes
Growing Tips, Tricks and FAQs
Growing Tips
Mustard greens, including Unzen Kobu, grow best in well-drained, fertile soil with a slightly acidic pH of around 6.0. They prefer cool weather and can even tolerate light freeze, which can enhance their flavor. Consistent moisture is crucial, so keep the soil evenly moist throughout the growing season.
When to Grow
For a spring crop, sow mustard seeds 2-4 weeks before the last expected freeze. For a fall harvest, plant seeds at the end of summer or early fall. In southern regions, you can plant mustard as late as September or October for a winter harvest. Be sure to complete the harvest before hot weather sets in, as high temperatures can cause the leaves to become tough and overly pungent.
How to Sow and Plant
Unzen Kobu prefers cool weather and can tolerate light freezes. For best results, plant in full sun to partial shade, 6-12 hours of sun daily, and ensure the soil is well-drained and rich in organic matter. Regular watering is essential to keep the soil consistently moist but not waterlogged.
How to Grow
Mustard greens need full sun to partial shade, 6-12 hours of sun daily. Maintain consistent watering, aiming for at least 1 inch of water per week. Use mulch to retain soil moisture and reduce weed growth. Fertilize with a nitrogen-rich fertilizer when the plants are 3-4 inches tall. Ensure good air circulation to prevent fungal diseases by watering at the base of the plants.
How to Save
Brassica juncea is capable of self pollinating, but insects can cross pollinate the flowers with other varieties of B. juncea if growing within a 2-mile radius. If saving seeds, isolate the plants from other B. juncea varieties by 2 miles.
To save the seeds, allow pods to brown, dry, and become crispy. Shake pods into a paper bag to remove seeds. Store seeds in a cool, dark, dry location.
FAQ
Can Unzen Kobu mustard tolerate frost?
Yes, mustard greens can tolerate light freeze; however, their ideal temperature is 50-80 degrees F.
When to harvest Unzen Kobu mustard?
It matures in around 45 days. Harvest individual leaves when they are young and tender, or cut the entire plant before it bolts.
What is the best way to store Unzen Kobu mustard?
Fresh mustard greens can be stored in the refrigerator for 2-3 weeks. They can also be frozen or dried for longer preservation. Mustard seeds can be saved for planting or culinary use.