Broccoli Seeds - Waltham 29 - Brassica oleracea

2, 3, 4, 5, 6, 7, 8, 9, 10, 11

USDA Zones 2-11: Grows as a cool-season annual across all zones. Planting times are critical and must be scheduled so the broccoli head matures in cool weather. Avoid the heat of summer, which causes the plant to "bolt" (flower) and become bitter.

Best Performance (Zones 3-8): This variety is specifically bred for a fall harvest. Plant in mid-summer to ensure the heads mature during the cool, shortening days of autumn. A light frost is not only tolerated but enhances the flavor.

Northern Zones (2-5): Starting seeds indoors is mandatory. For a fall crop (highly recommended), start seeds indoors in late spring/early summer and transplant out. For a spring crop (challenging), start seeds 6-8 weeks before the last frost and transplant outdoors 2-3 weeks before the last frost, using row covers.

Hot Climate Zones (9-11): This is an ideal fall and winter crop. Plant seeds in early fall (as temperatures begin to drop) and harvest throughout the mild winter. Do not attempt to plant in spring, as the increasing heat will cause immediate bolting.

Soil Temperature: Requires cool to moderate soil for germination. The optimal soil temperature is 60-75 degrees F, ensuring quick sprouting.

Growing Season: Requires a long, cool growing season of 85-100 days after transplanting. It must be timed so that the final 4-6 weeks of maturation occur when daytime temperatures are consistently below 75 degrees F.

Learn more about USDA Hardiness Zones here

When to Plant (Fall Crop - Highly Recommended):

Start seeds indoors 10-12 weeks before your average first fall frost date.

Transplant seedlings outdoors 6-8 weeks before your first fall frost. This allows the plants to establish themselves before the cool weather arrives, which is when they will form heads.

When to Plant (Spring Crop - More Challenging):

Start seeds indoors 6-8 weeks before your average last spring frost date.

Harden off seedlings and transplant them into the garden 2-3 weeks before your average last frost. Waltham 29 is frost-hardy, but a sudden summer heat wave can cause it to bolt.

Where to Plant:

Sunlight: Full sun is essential (6+ hours per day).

Soil: Broccoli is a very heavy feeder. Plant in rich, fertile, well-drained soil. Generously amend your planting bed with 3-4 inches of aged compost or well-rotted manure.

Soil pH: Prefers a soil pH between 6.0 and 7.0.

How to Plant (Seed Starting):

Depth: Plant seeds 1/4 inch deep in seed-starting mix.

Germination: Keep the soil evenly moist. Seeds will sprout in 5-10 days at 60-75 degrees F.

How to Plant (Transplanting):

Harden Off: Gradually acclimate your seedlings to outdoor conditions for 7-10 days.

Spacing: This is critical. Space plants 18-24 inches apart in rows that are 24-36 inches apart. This wide spacing is necessary to encourage large side-shoot production.

Plant Deep: Plant seedlings deep, burying the stem up to their first set of true leaves (just like a tomato).

Growing and Care:

Watering: Consistent moisture is key. Provide at least 1-1.5 inches of water per week. Drought stress can lead to small or bitter heads.

Mulching: Apply a 2-3 inch layer of organic mulch (such as straw or shredded leaves) after transplanting to keep the soil cool, retain moisture, and suppress weeds.

Fertilizing: As very heavy feeders, they need regular food. Feed with a nitrogen-rich liquid fertilizer (like fish emulsion or compost tea) every 3 weeks until the heads begin to form.

Harvesting:

Main Head: Harvest the central head when it is 5-8 inches wide and the flower buds are tight and dark green. Do not wait for them to turn yellow or spread apart. Cut the head off with 5-6 inches of stem.

Side Shoots: Do not pull the plant! After the main head is cut, the plant will begin to produce numerous smaller "side shoots" from the leaf axils.

Continuous Harvest: Continue to harvest these tender side shoots for several weeks, often until a hard, killing freeze (below 28 degrees F) finally stops the plant.