Broccoli Seeds - Waltham 29 - Brassica oleracea

3, 4, 5, 6, 7, 8, 9, 10, 11

USDA Zones 3-11 - Grows as a cool-season annual in all zones. Broccoli is a cool-weather crop that bolts (goes to seed) in extreme heat.

Best performance in Zones 3-9, where it can be grown in the spring and fall.

Northern zones (3-5) - Start seeds indoors 6-8 weeks before the last frost date for an early spring transplant. Plant outdoors 2-3 weeks before the last frost. For a fall crop, direct sow seeds in mid to late summer.

Hot climate zones (9-11) - Plant in late fall for a winter or early spring harvest. Avoid planting during the summer as the high temperatures will cause the plants to bolt before forming a head.

Soil temperature critical - Requires cool soil for germination, with optimal soil temperature between 50-80F. Germination is poor in hot soils.

Growing season needs - Requires 70-90 days to maturity from transplanting, making it a suitable crop for spring and fall gardens.

Learn more about USDA Hardiness Zones here

When to Plant:
Start seeds indoors 6-8 weeks before your last expected frost date for a spring harvest. You can also direct sow seeds outdoors in the fall, about 85-100 days before the first expected frost.

Location and Soil:
Choose a location that receives full sun (at least 6-8 hours of direct sunlight per day). In warmer climates, some afternoon shade can prevent bolting. Broccoli thrives in rich, well-draining soil with a good amount of organic matter. A soil pH between 6.0 and 7.0 is ideal.

Starting Seeds Indoors (Recommended for Spring):

Fill seed starting trays with a high-quality seed starting mix.

Sow seeds 1/2 inch deep.

Water to keep the soil consistently moist.

Once seedlings have their first true leaves, thin to one plant per cell.

Harden off seedlings for a week before transplanting.

Direct Sowing (Recommended for Fall):

Prepare a garden bed by loosening the soil and mixing in compost.

Sow seeds 1/2 inch deep, spacing them 2-3 inches apart.

Keep the soil consistently moist.

Once seedlings are established, thin them to 18-24 inches apart.

Care and Maintenance:

Watering: Provide consistent and even moisture throughout the growing season. Inconsistent watering can lead to stunted growth or split heads.

Fertilizing: Amend the soil with compost before planting. Broccoli is a heavy feeder, so a balanced, all-purpose fertilizer can be applied once a month.

Pests and Diseases: Watch for common pests like cabbage worms, cabbage loopers, and aphids. Consider using row covers to protect young plants. Good air circulation is important to prevent fungal diseases.

Harvesting: Harvest the main head when the florets are firm and tight, but before they start to yellow or separate. Use a sharp knife to cut the stalk below the head. Leave the plant in the ground, and it will produce smaller side shoots that you can continue to harvest.