How to Grow Waltham 29 Broccoli

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Waltham 29 Broccoli

Brassica oleracea var. italica

vegetable

Waltham 29 is a classic, cold-hardy broccoli cultivar developed at the University of Massachusetts that produces large, dense green head clusters followed by numerous side shoots. Known for exceptional cold tolerance and reliability, it has been a gardener favorite since its introduction in the 1950s. The variety is ideal for fall and winter harvests, continuing to produce even after light frosts.

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Example Waltham 29 Broccoli timeline · Pittsburgh, PA (Zone 6b)

Plant Waltham 29 Broccoli
Around Apr 17

Near Pittsburgh's average last spring frost.
Tend & protect
Late spring–summer

Watering, feeding, and pest-watch reminders.
Harvest Waltham 29 Broccoli
Around Jun 11

≈ 55 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Waltham 29 Broccoli dates for your own zip code.

Growing Conditions

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Sun: Full sun, 6-8 hours daily minimum

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Water: Consistent moisture; 1-1.5 inches per week. Keep soil evenly moist but not waterlogged. Mulch to retain soil moisture and regulate temperature.

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Spacing: 18 inches

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Days to maturity: 55-70 days from transplant

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Planting depth: 0.5 inches for seeds; transplants set at same depth as container

Soil

Type: Rich, well-draining loamy soil high in organic matter

pH: 6.0-7.5

Amendments:

Compost or well-rotted manure Balanced fertilizer (10-10-10) Calcium source (lime or gypsum) to prevent hollow stem

Growing Zones

Find your zone →

Thrives in zones 3-9, particularly suited to cool-season growing in fall and winter

3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a

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Growth Stages

Seedling

2-3 weeks

Small cotyledons emerge, followed by true leaves. Plants are delicate and light green.

Keep soil consistently moist. Provide bright light (12-16 hours) to prevent legginess. Thin seedlings to strongest specimens. Maintain temperature around 65-70°F.

Vegetative Growth

3-4 weeks

Plant develops 4-6 true leaves and establishes a robust rosette. Stems thicken and foliage deepens in color.

Harden off before transplanting. Space plants 18 inches apart. Begin weekly fertilization with balanced fertilizer. Water deeply and mulch around base. Watch for early pest activity.

Head Development

2-3 weeks

Central head forms as a tight cluster of unopened flower buds. Head can reach 4-6 inches in diameter with proper nutrition.

Maintain consistent watering (critical at this stage). Apply nitrogen-rich fertilizer every 2 weeks. Ensure full sun exposure. Monitor for yellowing or nutrient deficiency.

Head Maturity

1-2 weeks

Primary head reaches full size with compact, dark green florets. Head is firm and buds are tightly closed.

Begin harvesting when head is firm but before florets begin to loosen or flower. Harvest in early morning for best quality. Regular harvesting encourages side shoot development.

Side Shoot Production

4-8 weeks

After main head harvest, numerous smaller side shoots emerge from leaf axils along the stem. These shoots develop into mini-heads.

Waltham 29 is particularly generous with side shoots. Continue regular watering and fertilizing. Harvest side shoots when 4-6 inches long. Plants often remain productive through light frosts.

Companion Planting

Plan your garden →

Plant with:

Beets Carrots Chamomile Dill Garlic Lettuce Marigold Onions Potatoes Spinach Thyme

Avoid planting near:

Cabbage Cauliflower Kale Other brassicas (within 2 years in same location) Fennel Tomatoes (compete for similar nutrients and space)

Common Pests

Row covers before butterflies appear. Hand-pick caterpillars. Bacillus thuringiensis (Bt) spray. Plant aromatic herbs like thyme nearby.
Bacillus thuringiensis (Bt) effective on young larvae. Hand-pick larger caterpillars. Encourage parasitic wasps with flowering plants.
Row covers on young plants. Kaolin clay spray. Diatomaceous earth. Remove debris where beetles overwinter.
Strong water spray to dislodge. Insecticidal soap. Neem oil. Encourage beneficial insects like ladybugs.
Yellow sticky traps. Insecticidal soap. Neem oil. Reflective mulches.
Rotate crops (3-4 years). Lime to raise soil pH above 7.2. Remove infected plants immediately. Choose resistant varieties when possible.

Uses

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Fresh cooking and steaming

Culinary

Waltham 29 broccoli florets have a mild, slightly sweet flavor that becomes more tender when steamed or lightly boiled. The side shoots are particularly prized for their delicate texture and are excellent in stir-fries, roasted dishes, and fresh salads. [source]

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Preservation and storage

Culinary

This variety freezes exceptionally well, maintaining color and texture better than many cultivars. Blanch florets for 3 minutes, cool in ice water, and freeze for winter use. [source]

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Glucosinolate-rich superfood

Medicinal

Broccoli contains glucosinolates, compounds that convert to sulforaphane when chewed or cooked. Research suggests these compounds may support cellular health and detoxification pathways. [source]

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Kitchen waste reduction

Household

The extended side shoot production of Waltham 29 means a single plant provides multiple harvests over months, maximizing yield and reducing kitchen garden waste. [source]

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Pollinator and beneficial insect support

Wildlife

If you allow some florets to flower (they produce attractive yellow blooms), they provide nectar and pollen for bees and beneficial insects. The plant attracts parasitic wasps that prey on cabbage worms. [source]

This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.

Harvest Tips

Harvest the main head when it is firm, dense, and dark green, typically 6-8 weeks after transplanting. Cut the central head 6-8 inches below the florets with a sharp knife, leaving 6-8 inches of stem with leaves on the plant. Harvest in the morning after dew dries for best quality. After the main head is removed, side shoots will develop; harvest these when they reach 4-6 inches long. Waltham 29 continues producing side shoots until hard freeze (often down to 20°F). Regular harvesting encourages more side shoot production.

Fun Facts

🌱 Waltham 29 was developed at the University of Massachusetts and released in the 1950s specifically for cold climates and fall harvest; it remains one of the most reliable and popular heirloom broccoli varieties among home gardeners.
🌱 This variety can survive temperatures down to 20°F, making it ideal for extended fall and winter harvests; gardeners in cold climates can harvest fresh broccoli well after the first frost.
🌱 The side shoot production of Waltham 29 is remarkably generous—a single plant can produce 20-30 smaller heads after the main harvest, giving it an exceptional yield-to-space ratio compared to modern F1 hybrids.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Cultivar Full Sun Mulch Transplant True Leaves

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