Quick Growing Facts

When & Where to Grow ‘Waltham 29’ Broccoli

Broccoli grows best in cool conditions and prefers to mature in cool weather. ‘Waltham 29’ is especially suited to fall harvests and can handle chilly nights, but it also performs well in spring if heat arrives slowly.

• Spring crop (from transplants): Start seeds indoors 4–6 weeks before your last expected frost. Transplant outdoors 1–2 weeks before last frost when plants are sturdy and hardened off.
• Fall crop (often best): Start seeds indoors or in a protected nursery bed 10–12 weeks before first expected hard frost. Transplant out 6–8 weeks before frost so heads mature in cool weather.
• Direct sow (where seasons are mild): Sow directly in the garden when soil is at least 45–50°F (7–10°C) and weather is cool but not freezing.
• Location: Choose a sunny, open site with good air circulation and fertile, well-drained soil. Raised beds are ideal in heavy or poorly drained soils.

Soil Preparation

Broccoli is a heavy feeder. Rich, moist soil with plenty of organic matter supports strong growth and large, tight heads with lots of side shoots.

• Loosen the top 10–12 in (25–30 cm) of soil and remove weeds, roots, and stones.
• Incorporate generous amounts of compost or well-rotted manure before planting.
• For poor soils, work in a balanced organic fertilizer according to label rates at bed preparation.
• Broccoli prefers slightly acidic to neutral soil; if your soil is very acidic, a light application of garden lime can help.
• Form raised beds if drainage is poor; broccoli dislikes waterlogged roots.

Starting ‘Waltham 29’ Indoors

Starting broccoli indoors is the most reliable way to time harvests and avoid extreme weather during head formation.

• Sow 1–2 seeds per cell in trays or small pots filled with seed-starting mix, about 1/4 in (6 mm) deep.
• Keep at 65–75°F (18–24°C) with even moisture until germination, then provide strong light (bright window or grow lights).
• Thin to one strong seedling per cell or pot.
• When seedlings are 3–4 in (7–10 cm) tall, with 2–3 true leaves, begin hardening off over 5–7 days by gradually exposing them to outdoor conditions.

Transplanting & Spacing

Proper spacing gives each plant enough room to form a strong central head and many side shoots while maintaining good airflow to reduce disease.

• Transplant on a cool, cloudy day or in the evening to minimize stress.
• Set plants 18–24 in (45–60 cm) apart in rows 24–30 in (60–75 cm) apart.
• Plant seedlings slightly deeper than they were growing in pots, covering the stem up to the first true leaves.
• Water in thoroughly after transplanting to settle soil around roots.
• For smaller but more numerous heads, you can plant a bit closer (around 16–18 in / 40–45 cm apart).

Direct Sowing Broccoli Outdoors (Optional)

Direct sowing is possible in regions with long, mild seasons or for fall crops, though indoor starts are usually more reliable.

1. Sow seeds about 1/4–1/2 in (6–12 mm) deep in rows 24–30 in (60–75 cm) apart.
2. Sow seeds 3–4 in (8–10 cm) apart in the row.
3. Keep soil consistently moist until seedlings emerge.
4. Thin seedlings to 18–24 in (45–60 cm) apart once they have 2–3 true leaves. Use thinnings as tender microgreens or baby greens.

Watering & Feeding

Steady moisture and good nutrition are essential for tight heads and strong plants. Stress from drought or hunger can cause small, loose heads or premature flowering.

• Watering: Aim for about 1–1.5 in (2.5–4 cm) of water per week from rain and irrigation combined. Water deeply at the soil level rather than overhead when possible.
• Mulch: Apply a layer of compost, straw, or leaf mold around plants to conserve moisture, moderate soil temperature, and suppress weeds.
• Feeding: Side-dress with compost or a balanced organic fertilizer 3–4 weeks after transplanting, and again when heads begin to form, especially in poor soils.

Pests & Diseases

As a brassica, broccoli attracts similar pests to cabbage and kale. Early protection, regular monitoring, and good cultural practices go a long way toward keeping ‘Waltham 29’ healthy.

• Cabbage worms & loopers: Green caterpillars chew holes in leaves and heads. Hand-pick regularly or use organic Bt (Bacillus thuringiensis) according to label directions.
• Flea beetles: Tiny beetles that pockmark leaves with many small holes. Use floating row covers and maintain soil moisture.
• Aphids: Clusters on tender growth and in head crevices. Spray with a strong jet of water or use insecticidal soap if needed.
• Slugs & snails: Feed on young plants and lower leaves. Use traps, barriers, and hand-picking, especially in damp conditions.
• Clubroot & soil diseases: Avoid planting brassicas in the same bed more than once every 3–4 years. Improve drainage and maintain proper pH.

Harvesting ‘Waltham 29’ Broccoli

Main Head

• Harvest the central head when it is fully formed, tight, and deep green, but before individual flower buds begin to loosen or show yellow.
• Use a sharp knife to cut the head with 5–8 in (12–20 cm) of stem attached, making a slanted cut to shed water.
• Harvest in the cool of the morning for the best flavor and crispness.

Side Shoots

• After you remove the main head, ‘Waltham 29’ produces numerous smaller side shoots from leaf axils.
• Harvest side shoots frequently when they are 1–3 in (2.5–7.5 cm) across and still tight.
• Regular picking encourages ongoing production and extends the harvest window.

Storing & Using Broccoli

• Cool heads quickly after harvest by placing them in the shade or refrigerating promptly.
• Store in a breathable or lightly sealed bag in the refrigerator; use within about 5–7 days for the best flavor and texture.
• Broccoli can be blanched and frozen for long-term storage. Cut into florets, blanch briefly in boiling water, cool in ice water, drain, and freeze in portions.
• Use fresh broccoli for steaming, roasting, stir-fries, soups, pasta dishes, casseroles, and raw snacks with dips.

Saving Seed from Broccoli

Broccoli is a biennial that blooms in its second year after a period of cold. It is insect-pollinated and can cross with other Brassica oleracea crops (such as cabbage, cauliflower, kale, collards, and Brussels sprouts), so isolation is needed for pure seed.

• In cold climates, dig and store selected plants over winter or protect them heavily; replant or uncover in spring.
• Allow plants to flower and set seed; they produce yellow blossoms followed by slender pods.
• When pods turn tan-brown and dry, cut seed stalks into a paper bag or over a tray before they shatter.
• Dry thoroughly, then thresh pods to release seeds and winnow out chaff.
• Store seeds in a labeled, airtight container in a cool, dark, dry place. Under good conditions, broccoli seeds remain viable for several years.

Tips for Success

• Plan for heads to mature in cool weather (spring or fall) for the best quality and fewer bolting issues.
• Use row covers early to protect young plants from flea beetles and cabbage worms, especially in spring.
• Rotate brassicas to a new bed every 3–4 years to reduce disease and pest buildup.
• Feed and water consistently to avoid stress that leads to small, loose heads or premature flowering.
• Keep harvesting side shoots to extend the productive life of each plant and maximize your yield.

Note: Growing conditions and timing vary by region. Adjust sowing dates, watering, and heat or frost protection to match your local climate and weather patterns.