Why do radish bulbs split open?
Written by
Benjamin Miller
Reviewed by
Prof. Martin Thorne, Ph.D.For years, I was vexed by split radishes until I learned the science behind the cracks. The cambium layer grows faster than the outer skin in a sudden influx of water. My flooded garden, following a drought, was a case study where beautiful, firm globes became split disappointment overnight.
Primary Causes
- Irrigation fluctuations: Alternating dry/wet cycles
- Over-maturity: Delayed harvests
- Soil compaction: Restricts even root expansion
Prevention Tactics
- Drip irrigation: Maintains steady moisture
- Mulching: Regulates soil temperature
- Timed harvests: Check roots daily after day 20
Xylem cells take on water without moderation after dry periods, bursting through their epidermal layers. To counter this, I am watering daily---twice daily during particularly hot periods---at 6 AM and again at 5 PM, using a 2-gallon pump sprayer. To maintain a moisture content of about 40-60%, I use soil moisture meters, which prevent deterioration in conditions over 2-3 days without a drastic shift.
Immediate Action
- Harvest split radishes within 4 hours
- Refrigerate in damp towels
- Trim damaged sections before cooking
Long-Term Fixes
- Amend soil with 30% vermiculite
- Plant bolt-resistant varieties
- Schedule irrigation using weather apps
Avoid splitting of radishes or Radish splitting by thinning your seedlings early. Crowded seedlings result in varying growth patterns. I had a rule of somewhat-inspiring artistic types spread 3 inches apart for round types and 6 inches for daikon. When you need to remove excess seedlings, use surgical scissors, since pulling seedlings up may disturb the roots of nearby seedlings. Perform nightly inspections when seedlings begin flowering to catch small splits before they become larger.
Read the full article: How to Grow Radishes: 7 Pro Tips for Bumper Harvests
