Why does broccoli form small, loose heads?
Written by
Nguyen Minh
Reviewed by
Prof. Charles Hartman, Ph.D.When broccoli feels any kind of stress, whether it be heat, drought, or poor nutrition, the heads will stay small and loose.I learned this firsthand when my first crop failed like this. After some research, I found out that 75°F (24°C) causes early flowering in broccoli. Consistent care will eliminate this problem. Let's discuss the primary offenders and how to combat them.
Temperature Stress
- Heads bolt above 75°F (24°C)
- Night temps over 60°F (15°C) disrupt growth
- Use shade cloth during midday heatwaves
Watering Issues
- Inconsistent moisture splits stems
- Soil should stay damp 2 inches deep
- Drip irrigation prevents drought stress
Soil Deficiencies
- Low nitrogen limits head size
- Test soil before planting
- Side-dress with blood meal at 3 weeks
Overcrowding
- Plants under 18 inches apart compete
- Prune lower leaves for airflow
- Thin seedlings early to prevent stunting
Mulching controls both the moisture and temperature of the soil. I use shredded leaves around the stems of broccoli to keep its roots cool during times of elevated heat. In my zone 7 garden this provided approximately 2 additional weeks for harvesting before the summer heat caused the plants to bolt.
Regular watering is essential. I installed a drip system with a timer to guarantee it has even moisture. I check the soil with a moisture meter, below 5 means it is time to water. Overhead sprinklers are good as they risk mildew and watering only at the base is a good way to prevent mildew.
Read the full article: How to Grow Broccoli: Expert Tips for Home Gardens
