When to Plant Kohlrabi for Tender Spring and Fall Stems

Quick answer

Kohlrabi is a cool-season crop grown for an enlarged stem, not a root. Direct-sow about 4–2 weeks before the last spring freeze reference, or start seed indoors about 6–4 weeks before it for transplanting into workable soil. For fall, begin about 10–8 weeks before the first fall freeze reference. Use the planting calendar for local ranges, then check the forecast alongside soil temperature and current bed conditions.

Planting methods

Kohlrabi can be direct-sown or started indoors. University of Minnesota Extension advises starting indoor seedlings about four to six weeks before transplanting and direct-sowing again in July for a fall crop in Minnesota. Illinois Extension also supports small spring sowings and one or two midsummer plantings.

Those state dates describe local examples, not a national calendar. In spring, wait for workable soil and harden transplants. In summer, protect the shallow seedbed from heat and drying while seedlings establish.

Spacing, depth, and maturity

Sow seed about 1/4–1/2 inch deep. Thin standard plants to roughly 2–5 inches apart; named giant types can require a wider final spacing from their packet. Typical varieties may mature in about 35–60 days. Harvest standard types when the enlarged stem is roughly 2–3 inches wide unless the variety guidance says otherwise, because overgrown stems can become tough, woody, or bitter.

Worked local-calendar example

With an April 19 last spring freeze reference, a 4–2 week direct-sow range falls from late March into early April. With an October 23 first fall freeze reference, a 10–8 week range falls from mid-August into late August. These are planning examples, not fixed planting dates or a guarantee that heat-stressed seedlings will mature on schedule.

Common mistakes

• Burying the enlarged stem as though kohlrabi were a root crop.
• Letting shallow summer sowings dry during emergence.
• Waiting for standard kohlrabi to become very large before checking tenderness.

Limitations

Variety, intended harvest size, heat, moisture, pests, transplant stress, and protection affect growth. USDA Zones describe winter extremes, while NOAA freeze normals describe historical probabilities rather than forecasts. Neither replaces the short-range forecast, soil temperature, or current bed conditions.