Waltham 29 Broccoli
Brassica oleracea var. italica 'Waltham 29'
Developed at the University of Massachusetts, this cold-hardy broccoli variety was specifically bred to extend the growing season well into winter in northern climates. It produces medium-sized, deep blue-green heads followed by an abundance of tender side shoots that can be harvested for weeks. This reliable performer is perfect for gardeners wanting fresh broccoli through the fall and early winter months.
Harvest
65-74d
Days to harvest
Sun
Full sun to partial shade
Zones
6–9
USDA hardiness
Height
10-24 inches
Planting Timeline
Showing dates for Waltham 29 Broccoli in USDA Zone 7
All Zone 7 brassica →Zone Map
Click a state to update dates
Waltham 29 Broccoli · Zones 6–9
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 1 | April – May | June – July | June – July | August – September |
| Zone 2 | April – May | June – July | May – July | July – September |
| Zone 11 | January – January | January – February | January – February | February – December |
| Zone 12 | January – January | January – February | January – February | February – December |
| Zone 13 | January – January | January – February | January – February | February – December |
| Zone 3 | March – April | May – June | May – June | July – October |
| Zone 4 | March – April | May – June | April – June | July – October |
| Zone 5 | February – March | April – May | April – May | June – November |
| Zone 6 | February – March | April – May | April – May | June – November |
| Zone 7 | February – March | April – May | March – May | May – November |
| Zone 8 | January – February | March – April | March – April | May – December |
| Zone 9 | January – January | February – March | February – March | April – December |
| Zone 10 | January – January | February – March | January – March | March – December |
Succession Planting
Waltham 29 stalls and buttons — forming small, premature heads — once daytime temperatures push above 80°F consistently, so the succession window is real but short on each end. In zone 7, start seeds indoors in late February to early March, transplant out in April, and make a second sowing no later than mid-May for a late-spring run. For fall, count back 74 days from your first expected frost and start transplants indoors in late July; they go out in August and head up during the cooler weeks of October and November.
Don't try to push a third planting into midsummer. Two successions per year — one spring, one fall — is the practical limit in most of zone 7, and trying to split the difference just means a bed full of bolted plants in August.
Complete Growing Guide
Waltham 29's cold-hardiness demands reverse-season timing: plant in mid-to-late summer for a fall-to-winter harvest rather than spring planting, since this cultivar truly thrives as temperatures drop below 60°F. Unlike heat-loving broccoli varieties, it won't bolt prematurely in autumn's cooling weather—in fact, cold exposure sweetens the flavor by converting starches to sugars. Plant in full sun with rich, well-draining soil amended with nitrogen to support both the primary head and the vigorous side-shoot production this variety is known for. Watch for cabbage loopers and imported cabbageworms, which remain active through fall; use row covers during establishment or organic pest management as needed. To maximize your harvest window, plant succession crops every two weeks through late summer so you'll have staggered maturity dates extending well into December in northern climates. One essential tip: delay harvesting the main head slightly longer than you would other varieties—allowing it to grow to full size ensures the strongest side-shoot production afterward, giving you weeks of continued harvests.
Light: Full sun (6 or more hours of direct sunlight a day), Partial Shade (Direct sunlight only part of the day, 2-6 hours). Soil: Clay, Loam (Silt), Sand. Soil pH: Acid (<6.0), Neutral (6.0-8.0). Drainage: Good Drainage, Moist. Height: 0 ft. 10 in. - 2 ft. 0 in.. Spread: 1 ft. 0 in. - 2 ft. 0 in.. Spacing: 12 inches-3 feet. Growth rate: Medium. Maintenance: Medium. Propagation: Seed, Stem Cutting. Regions: Coastal, Mountains, Piedmont.
Harvesting
Harvest Waltham 29 broccoli when the main head reaches 4-6 inches in diameter and displays that characteristic deep blue-green color with tightly clustered, unopened florets that feel firm to the touch. Cut the central head when buds are still compact, before any yellow flowers appear, which signals peak tenderness and flavor. This variety excels in providing continuous harvests: after removing the main head, the plant will produce abundant side shoots for weeks, allowing you to return every few days for tender secondary heads. For best results in cold climates, time your main harvest before the first hard freeze, as the side shoots that follow are surprisingly frost-tolerant and often taste sweeter after light frost exposure.
The fruits dry and split when ripe.
Color: Brown/Copper, Green. Type: Siliqua. Length: > 3 inches.
Garden value: Edible
Harvest time: Fall, Summer
Edibility: The foliage is edible raw or cooked but when cooked can emit an unpleasant odor.
Storage & Preservation
Fresh Waltham 29 heads store best unwashed in perforated plastic bags in your refrigerator's crisper drawer at 32-35°F with high humidity. Properly stored heads maintain quality for 7-10 days, while tender side shoots should be used within 3-4 days. For longer storage, blanch florets in boiling water for 2-3 minutes, shock in ice water, drain thoroughly, and freeze in sealed bags for up to 12 months. The sweet, nutty flavor of Waltham 29 makes it excellent for fermentation – try making broccoli kimchi or adding to mixed vegetable ferments. You can also dehydrate blanched florets at 125°F for 8-12 hours to create nutritious additions to soups and casseroles.
History & Origin
Developed by the University of Massachusetts Vegetable Breeding Program during the mid-twentieth century, Waltham 29 emerged as part of systematic efforts to create cold-hardy brassicas suited to northeastern growing conditions. The variety represents the university's commitment to extending the commercial and home gardening season in cold climates, though detailed records of its specific breeder and exact year of release remain limited in readily available horticultural documentation. Waltham 29 became part of a broader lineage of cold-tolerant broccoli cultivars that prioritized winter hardiness and side-shoot production, establishing itself as a reliable standard for northern gardeners seeking season extension into late fall and early winter months.
Origin: W. Europe
Advantages
- +Extended harvest season into winter with cold-hardy genetics from UMass breeding
- +Abundant side shoots provide weeks of continued harvesting after main head
- +Sweet, nutty flavor with excellent texture and minimal bitterness compared to alternatives
- +Moderate difficulty level makes it accessible for most home gardeners
- +Medium-sized heads suit small to medium garden spaces and household portions
Considerations
- -Susceptible to multiple brassica diseases including clubroot, black rot, and downy mildew
- -High pest pressure from cabbage worms, aphids, flea beetles, and cabbage loopers requires management
- -Requires consistent moisture and well-draining soil to prevent clubroot disease development
Companion Plants
Nasturtiums pull aphids off your broccoli by being a more attractive target — aphids pile onto nasturtium stems instead, where you can spot and cut the whole stem out before the colony migrates. French marigolds, planted densely, suppress soil nematode populations over a full season. Dill draws in parasitic wasps from the Braconidae family that lay their eggs inside cabbageworm larvae; once you've watched one work, you'll stop pulling your dill. Onions and celery planted around the perimeter put out enough competing scent that cabbage white butterflies (Pieris rapae) have a harder time locking onto a landing spot.
Mustard is the pairing that surprises people: it's a brassica, so it shares the same disease and pest pressures as Waltham 29, and growing them together concentrates clubroot risk and gives caterpillar populations a larger buffet. Tomatoes are a problem mostly through competition — they're aggressive feeders and will shade a broccoli plant faster than expected, especially at the 18-24 inch spacing both crops need.
Plant Together
Nasturtiums
Acts as trap crop for aphids and flea beetles, repels cabbage worms
Marigolds
Repels cabbage moths and other brassica pests with strong scent
Dill
Attracts beneficial wasps that parasitize cabbage worms
Onions
Repels cabbage maggots and aphids with sulfur compounds
Celery
Repels cabbage white butterflies and improves soil structure
Lettuce
Grows well in broccoli's shade and doesn't compete for nutrients
Spinach
Shallow roots don't compete, benefits from broccoli's nitrogen fixation
Chamomile
Attracts beneficial insects and may improve broccoli flavor
Keep Apart
Tomatoes
Allelopathic compounds inhibit brassica growth and development
Strawberries
Compete for similar nutrients and may stunt broccoli growth
Mustard
Attracts same pests like flea beetles and cabbage root fly
Nutrition Facts
Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #747447)
Pests & Disease Resistance
Resistance
Good cold tolerance and resistance to bolting. Moderate resistance to common broccoli diseases.
Common Pests
Cabbage worms, aphids, flea beetles, cabbage loopers
Diseases
Clubroot, black rot, downy mildew, alternaria leaf spot
Troubleshooting Waltham 29 Broccoli
What you'll see, why it happens, and what to do about it.
Small, ragged holes chewed through leaves, sometimes leaving a lacy skeleton — most visible on young transplants in spring
Likely Causes
- Imported cabbageworm (Pieris rapae larvae) — the white butterfly you see fluttering around the bed is laying eggs on the undersides of leaves
- Cabbage looper (Trichoplusia ni) — a separate species but does the same damage; look for the looping crawl to tell them apart
What to Do
- 1.Hand-pick caterpillars and egg clusters in the morning when they're easiest to spot
- 2.Spray Bt (Bacillus thuringiensis) every 5-7 days while caterpillars are actively feeding — it breaks down in sunlight so timing matters
- 3.Cover transplants with row cover immediately after planting and leave it on until heads start forming
Tiny, irregular pitting and shot-hole damage on seedling leaves, worst in dry weather right after transplanting
Likely Causes
- Flea beetles (Phyllotreta spp.) — tiny, shiny, jumping beetles that are most damaging to plants under 6 inches tall
- Drought stress — dry soil slows the plant's ability to outgrow the feeding damage
What to Do
- 1.Use row cover for the first 3 weeks after transplanting — flea beetles hit hardest on young plants and the crop usually grows past the pressure once it clears 18 inches
- 2.Keep soil consistently moist; a stressed transplant takes far longer to recover from flea beetle feeding
- 3.Dust diatomaceous earth around the base of plants to reduce beetle movement, but reapply after every rain
Yellowing leaves and stunted growth, with roots that look swollen and knobbly rather than clean and fibrous
Likely Causes
- Clubroot (Plasmodiophora brassicae) — a soil-borne pathogen that can persist in the soil for 20 years or more once established
- Acidic soil below pH 6.0, which favors clubroot spore germination
What to Do
- 1.Pull and bag the entire plant — roots and all — and put it in the trash, not the compost
- 2.Lime the bed to raise soil pH to at least 6.8-7.0; clubroot activity drops significantly above that range
- 3.Rotate out of all brassicas (broccoli, cabbage, kale, turnips) for a minimum of 4 years in that bed
Dark, water-soaked spots on older leaves expanding into tan or brown lesions with yellow halos, appearing during wet or humid stretches
Likely Causes
- Alternaria leaf spot (Alternaria brassicicola or A. brassicae) — a fungal disease that spreads through water splash and infected seed
- Downy mildew (Peronospora parasitica) — produces similar upper-leaf spotting but shows grayish-purple fuzz on leaf undersides in cool, wet conditions; distinct from Alternaria
What to Do
- 1.Strip and trash affected leaves at first sign — don't compost them
- 2.Switch to drip irrigation or water at the base of plants; keeping foliage dry cuts fungal spread significantly
- 3.Give plants their full 18-24 inch spacing — crowded plants stay wet longer and both pathogens move faster through dense canopies
Frequently Asked Questions
How long does Waltham 29 broccoli take to grow?▼
Can you grow Waltham 29 broccoli in containers?▼
What does Waltham 29 broccoli taste like?▼
Is Waltham 29 broccoli good for beginners?▼
When should I plant Waltham 29 broccoli for fall harvest?▼
How cold can Waltham 29 broccoli tolerate?▼
Growing Guides from Wind River Greens
Where to Buy Seeds
Sources & References
External authority sources used in compiling this guide.
See the Methodology page for how this data is sourced, what's AI-assisted, and known limitations.