A young broccoli plant forms a head before it has fully matured. The stem is narrow, and the head is too small.
Cold weather causes young broccoli plants to produce small heads. Other possible causes are dry soil, lack of nutrients in the soil, overcrowding, or damage to the roots. Pot-bound seedlings may also produce small heads as a result of a lack of nutrients and room for roots to expand.
Meet broccoli’s water and nutrient needs, control diseases and insects, acclimate young plants to cold, and time plantings.
Don’t let the soil dry out; water when the soil is dry 1 inch below the surface. Use an organic mulch to reduce evaporation.
Check for signs of disease or insect damage.
Acclimate your seedlings, hardening them off by gradual exposure to the cold. Transplant them before they are seven weeks old, but when it’s not likely to stay below 50°F for 10 days or more. Space your variety as the seed packet directs. Fertilize seedlings according to packet directions.
To prepare for future plantings, add 3 to 4 inches of organic matter to the soil.
In mild-winter areas, plant a crop in late summer or early fall so plants can mature before cool weather causes head growth.