How to Grow Broccoli Marathon

Broccoli Marathon

Brassica oleracea var. italica

vegetable

Broccoli Marathon is a hybrid cultivar known for its exceptional heat tolerance and ability to produce consistently high-quality heads even in challenging growing conditions. This variety produces large, tight green heads with excellent flavor and extended harvest windows. It's particularly valued by home gardeners and commercial growers for its reliability and disease resistance.

Growing Conditions

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Sun: Full sun, 6-8 hours daily minimum; tolerates partial shade in hot climates

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Water: Consistent moisture; 1.5-2 inches per week. Keep soil evenly moist but not waterlogged. Avoid water stress during head development.

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Spacing: 18-24 inches apart in rows 24-30 inches apart inches

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Days to maturity: 55-75 days from transplant

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Planting depth: 0.25 inches for seeds; transplants planted at same depth as original pot

Soil

Type: Rich, well-draining loamy soil

pH: 6.0-7.5

Amendments:

compost aged manure nitrogen-rich fertilizer bone meal

Growing Zones

Find your zone →

Thrives in zones 3-9, with exceptional performance in zones 5-8

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

Growth Stages

Seedling

3-4 weeks

Small plants with 2-4 true leaves, developing root system

Keep soil consistently moist. Provide bright light (14-16 hours). Maintain temperatures 65-75°F. Thin seedlings to prevent crowding.

Vegetative/Establishment

2-3 weeks indoors; 1-2 weeks post-transplant

Plants developing 6-12 leaves, establishing strong root systems and main stems

Begin hardening off 7-10 days before transplanting. Apply balanced fertilizer every 2 weeks. Monitor for early pest infestations.

Pre-flowering/Head Formation

2-3 weeks

Plants are bushy with numerous leaves; central head begins to develop and expand

Increase nitrogen fertilizer as head forms. Maintain consistent watering—critical for head quality. Mulch around base to retain moisture. Watch for pest activity.

Head Development/Maturity

2-3 weeks

Central head enlarges with tight, compact green florets forming a large dome; side shoots begin developing

Continue consistent watering and fertilization. Keep soil moist but not waterlogged. Provide shade cloth in extreme heat (>85°F) if needed. Begin harvesting when head is firm.

Secondary Harvest

3-4 weeks

After central head removal, side shoots develop into smaller secondary heads

Continue watering and light fertilization. Side shoots will mature in 10-20 days. Maintain plants for extended harvest period.

Companion Planting

Plan your garden →

Plant with:

beets celery chard dill garlic marigold nasturtium onion oregano potatoes thyme

Avoid planting near:

beans fennel kale other brassicas (within 1 year rotation) pole beans strawberries tomatoes

Common Pests

Use row covers on young plants. Bt (Bacillus thuringiensis) spray weekly starting at transplant. Hand-pick caterpillars. Remove infested plant parts.
Apply Bt or spinosad weekly. Use pheromone traps for monitoring. Hand-pick large caterpillars. Encourage parasitic wasps.
Use row covers on seedlings. Diatomaceous earth on foliage. Neem oil spray. Plant trap crops (radishes).
Strong water spray to dislodge. Insecticidal soap spray. Neem oil. Encourage beneficial insects like ladybugs and parasitic wasps.
Practice 4-year crop rotation. Maintain soil pH 6.8-7.2. Avoid waterlogging. Remove infected plants. Sterilize tools.
Improve air circulation. Water at soil level only. Remove lower infected leaves. Apply sulfur or copper fungicide. Ensure good drainage.

Uses

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Steaming, roasting, and raw consumption

Culinary

Broccoli Marathon produces tender, flavorful heads excellent for steaming, roasting with olive oil, stir-frying, or serving raw with dips. The tight florets and robust stems make it versatile for various cooking methods. [source]

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Immune and cancer-fighting compounds

Medicinal

Broccoli is rich in sulforaphane, a compound with documented anti-cancer properties. It also provides high levels of vitamin C, vitamin K, and antioxidants that support immune function. [source]

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Nutritional supplementation and health

Household

As a nutrient-dense vegetable, broccoli serves as a staple in healthy diets providing fiber, folate, potassium, and various phytonutrients that support overall wellness. [source]

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Freezing and preservation

Culinary

Broccoli Marathon's large, well-formed heads freeze excellently after blanching, making it ideal for long-term storage and winter use. [source]

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Pollinator and beneficial insect habitat

Wildlife

If allowed to bolt and flower, broccoli flowers attract bees, butterflies, and beneficial insects that support garden ecosystems. [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 central head when it is firm, compact, and dark green, typically 8-12 inches in diameter, before florets begin to loosen or yellow. Cut the main head 5-7 inches below the head with a sharp knife in the early morning. This variety's exceptional heat tolerance means heads can remain on plants longer without premature bolting. After main head removal, side shoots will develop and mature in 10-20 days for secondary harvests. Continue harvesting until first hard frost or until plants decline.

Fun Facts

🌱 Broccoli Marathon was specifically bred for heat tolerance and can produce quality heads in temperatures and conditions that cause other varieties to bolt prematurely—making it excellent for spring and fall gardens in warm climates.
🌱 The 'head' of broccoli is actually composed of hundreds of unopened flower buds clustered together; harvesting before it flowers allows you to eat the plant at its peak nutritional density.
🌱 After you cut the main head, broccoli Marathon will reliably produce 4-8 side shoots that can be harvested individually, effectively extending your harvest season from a single plant for 6-8 weeks.

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