Mammoth Dill
Lathyrus odoratus
Mammoth Dill is a vigorous heirloom herb variety known for its tall, robust growth and abundant foliage. Plants reach full maturity in approximately 90 days, producing large, feathery fronds that tower above standard dill varieties. The distinctive flavor combines fresh, tangy notes with subtle caraway undertones and a hint of sweetness, making it exceptional for pickling, dill weed, and culinary applications. Mammoth Dill thrives in full sun with rich, well-drained soil and is remarkably easy to grow, making it ideal for both experienced and novice gardeners seeking impressive yields.
Harvest
90d
Days to harvest
Sun
Full sun
Zones
2–11
USDA hardiness
Height
3-8 feet
Planting Timeline
Showing dates for Mammoth Dill in USDA Zone 7
All Zone 7 herb →Zone Map
Click a state to update dates
Mammoth Dill · Zones 2–11
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 2 | April – May | June – August | — | August – September |
| Zone 11 | January – January | January – March | — | March – December |
| Zone 3 | April – May | June – July | — | July – October |
| Zone 4 | March – April | June – July | — | July – October |
| Zone 5 | March – April | May – June | — | June – October |
| Zone 6 | March – April | May – June | — | June – November |
| Zone 7 | February – March | April – June | — | June – November |
| Zone 8 | February – March | April – May | — | May – December |
| Zone 9 | January – February | March – April | — | April – December |
| Zone 10 | January – January | February – April | — | April – December |
Succession Planting
Dill bolts fast once heat sets in — once daytime highs are consistently above 85°F, it's going to seed whether you want it to or not. In zone 7, transplants from an April start will have harvestable fronds by June, but by mid-July most plants are done as a leaf crop. To keep fresh dill coming, set out transplants every 14–21 days starting April 1 through late May, then pause through the worst of summer heat and resume again in late August through mid-September once nighttime temps drop back below 70°F.
If you're growing primarily for seed — pickling dill, mostly — one or two plantings in late April are enough. Just let them run to flower and set seed, then harvest the umbels when the seeds turn tan and start to loosen. For continuous frond harvest, the succession cadence matters a lot more: a single planting gives you maybe 3–4 weeks of good cutting before the plant shifts its energy toward flowering.
Complete Growing Guide
Mammoth Dill seeds should be started indoors 4 to 6 weeks before your last frost date, as this variety benefits from an early head start to reach its full 3 to 8 feet height before the growing season peaks. Alternatively, you can direct sow seeds outdoors 2 weeks after your last frost date into warm soil. Seeds germinate best when planted ¼ inch deep in moist soil and kept consistently warm. Whether sowing indoors or out, ensure your seedlings receive plenty of light to prevent the weak, leggy growth that often compromises taller cultivars.
Prepare your soil by working in compost or well-rotted organic matter to create loose, fertile ground that drains well yet retains moisture. Space Mammoth Dill plants 12 inches apart to allow adequate air circulation around the foliage, which helps prevent the powdery mildew and bacterial leaf spot this variety is particularly susceptible to in humid conditions. The soil pH should ideally fall between 6.0 and 7.0. Given that Mammoth Dill reaches substantial heights, ensure your planting location receives at least 6 hours of full, direct sun daily for vigorous growth and optimal blooming.
Water regularly throughout the season, providing about 1 to 1.5 inches per week through rainfall or irrigation. Keep the soil consistently moist but not waterlogged, as overly wet conditions invite damping off in seedlings and fungal problems in mature plants. Feed your plants every three weeks with a balanced, water-soluble fertilizer once they're established, switching to a lower-nitrogen formula once flowering begins to encourage abundant blooms rather than excessive foliage.
Mammoth Dill attracts aphids and carrot rust flies, so monitor undersides of leaves regularly and remove affected foliage promptly. Carrot rust fly larvae can damage roots, making crop rotation essential—avoid planting in areas where carrots or parsley grew recently. Watch for parsley worms, which are the caterpillars of swallowtail butterflies; while beneficial insects, they can defoliate plants if populations surge. Hand-picking is often sufficient unless infestations become severe.
One critical technique gardeners overlook with Mammoth Dill is proper trellising. This cultivar's height demands sturdy support from the outset; install stakes or a trellis system when plants are young to prevent wind damage and allow air to circulate beneath the canopy, reducing disease pressure. Pinch back the growing tips when plants reach 6 inches to encourage bushier, more floriferous growth rather than a single tall stem.
A frequent mistake is assuming Mammoth Dill requires minimal water because it's an herb. Unlike smaller dill varieties, this tall cultivar has substantial water demands to support its vigorous growth and prolonged blooming period over the full 90-day season. Inconsistent watering stress can trigger bolting and reduce flower production, so establish a regular watering routine early and maintain it faithfully.
Harvesting
Peak readiness for Mammoth Dill occurs when the 2-inch blossoms display fully saturated color in their red, purple, mauve, pink, blue, or white hues, and the petals feel papery-thin yet supple to the touch. Harvest in the morning after dew dries but before afternoon heat intensifies the blooms' fragrance compounds. For continuous production throughout the 90-day season, pick flowers regularly using a continuous-harvest pattern rather than stripping the plant at once; this stimulates more blossom development. Clip stems just above a leaf node with sharp scissors to encourage branching. Avoid harvesting more than one-third of the plant at any single time to maintain vigor and extend the blooming period. Fresh flowers should be used immediately or placed in cool water within minutes of cutting for maximum flavor and fragrance preservation.
Type: Legume.
Edibility: Sweet pea fruits are inedible and poisonous to humans.
Storage & Preservation
Fresh dill fronds stay crisp for 7-10 days when stored like cut flowers – trim stems and place in water in the refrigerator, covering loosely with a plastic bag. For longer storage, wrap clean, dry fronds in damp paper towels and refrigerate in sealed containers for up to 2 weeks.
Freeze fresh dill by chopping and packing into ice cube trays with water or olive oil – perfect for adding to soups and stews. Alternatively, freeze whole sprigs in freezer bags for up to 6 months, though texture becomes soft upon thawing.
Dry dill seeds by hanging cut seed heads upside down in paper bags in a warm, dry location. Seeds are fully dry when they crack rather than bend when pressed. Store dried seeds in airtight containers for up to 2 years. The abundant seed production of mammoth dill makes it excellent for sharing with fellow gardeners or saving for next season's planting.
History & Origin
The origins of Mammoth Dill remain largely undocumented in standard horticultural records, though the variety belongs to the broader heritage of sweet pea (Lathyrus odoratus) breeding that flourished during the Victorian era and continued through the twentieth century. The "Mammoth" designation suggests deliberate selection for larger flower size, a trait breeders prioritized throughout sweet pea development. The variety's characteristics—notably its exceptional fragrance and extended bloom period—align with goals emphasized by major seed companies including Burpee and Ferry's during their sweet pea breeding programs. Without specific breeder attribution or introduction date documented in available sources, Mammoth Dill likely represents a commercial cultivar developed and maintained within the broader American or European seed industry's sweet pea lines.
Origin: Southern Italy, Sicily, Crete
Advantages
- +Large fragrant blossoms attract hummingbirds and pollinators to your garden
- +Fresh tangy flavor with unique caraway notes enhances culinary dishes
- +Long blooming period over 90 days provides extended harvest window
- +Easy to grow variety suitable for beginning and experienced gardeners
- +Bright vibrant colors in red, purple, pink, blue, and white
Considerations
- -Vulnerable to multiple pests including aphids, carrot rust flies, and parsley worms
- -Susceptible to powdery mildew and bacterial leaf spot diseases
- -Prone to damping off fungal disease in overly wet conditions
Companion Plants
Cabbage, broccoli, and Brussels sprouts are the strongest companions for dill. Dill's flat-topped flower umbels — once they open around day 70 or so — draw in parasitic wasps from the Braconidae family that hunt the caterpillars chewing through brassica leaves. It's a functional relationship, not just a pleasant one. Tomatoes and cucumbers benefit from that same predatory insect activity, and dill doesn't crowd them at the roots since it stays relatively shallow while those crops are pulling from deeper down. In our zone 7 Georgia garden, where both imported cabbageworm and tomato hornworm pressure stack up through July and August, having dill in bloom along the bed edges pays off in a way you can actually see.
Keep dill away from carrots. Both are Apiaceae, and if they flower at the same time they'll cross-pollinate — which ruins any seed you were saving and muddies the dill flavor. Fennel is a different problem: it produces allelopathic compounds that stunt a wide range of nearby vegetables, and dill planted within a few feet of it tends to grow poorly and bolt early. Give them completely separate beds, not just a few extra inches of spacing.
Plant Together
Cabbage
Dill repels cabbage worms and other brassica pests
Tomatoes
Dill attracts beneficial insects that control tomato hornworms and aphids
Cucumbers
Dill repels cucumber beetles and attracts pollinators
Lettuce
Dill provides light shade and repels aphids that attack lettuce
Onions
Onions repel dill's pest insects while dill attracts beneficial predators
Broccoli
Dill attracts wasps that parasitize cabbage worms and aphids
Brussels Sprouts
Dill deters cabbage loopers and imported cabbage worms
Corn
Dill attracts beneficial insects that control corn earworm and aphids
Keep Apart
Carrots
Can stunt carrot growth and may cross-pollinate with wild carrots
Fennel
Both are umbellifers that compete for resources and may cross-pollinate
Cilantro
May bolt prematurely when grown near mature dill plants
Nutrition Facts
Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #172233)
Pests & Disease Resistance
Resistance
Generally disease resistant, avoid overhead watering
Common Pests
Aphids, carrot rust fly, parsley worm
Diseases
Damping off, bacterial leaf spot, powdery mildew
Troubleshooting Mammoth Dill
What you'll see, why it happens, and what to do about it.
Seedlings collapse at the soil line — stems look pinched or water-soaked, sometimes with fuzzy white mold on the soil surface
Likely Causes
- Damping off — a complex of soil-borne pathogens (Pythium, Rhizoctonia, Fusarium) that thrive in cold, wet, poorly-drained seed-starting mix
- Overwatering or trays sitting in standing water after indoor sowing
What to Do
- 1.Pull and discard affected seedlings immediately — they won't recover
- 2.Let the top half-inch of seed-starting mix dry out between waterings, and make sure trays drain freely
- 3.Next round, start with fresh, sterile seed-starting mix and clean trays; don't reuse last year's mix
White powdery coating on leaves, usually showing up mid-summer on older foliage first
Likely Causes
- Powdery mildew — a fungal disease that spreads by airborne spores and thrives in warm days with cool nights, especially in crowded plantings with poor airflow
- Plants spaced too close (under 6 inches) or shaded by taller neighbors
What to Do
- 1.Mix 1 tablespoon baking soda plus 1 tablespoon summer horticultural oil in 1 gallon of water and spray as a preventive every 3 to 5 days — NC State Extension's organic gardening guidance notes this combination is effective against powdery mildew without harsh synthetics
- 2.Strip and trash the worst-affected leaves to slow spread
- 3.Thin plants to at least 9–12 inches apart so air can move through; Mammoth Dill hits 3 to 8 feet tall and the canopy closes faster than most people expect
Clusters of small soft-bodied insects on new growth or flower umbels, leaves curling or sticky to the touch
Likely Causes
- Aphids — most likely Cavariella aegopodii, the carrot-willow aphid, which specifically targets plants in the Apiaceae family including dill
- Ant activity nearby — ants tend aphid colonies and will physically relocate them to new growth
What to Do
- 1.Knock aphids off with a firm spray of water from the hose; repeat every 2–3 days until numbers drop
- 2.If populations persist after 5–6 days, apply insecticidal soap directly to the colonies — coat the undersides of leaves where they shelter
- 3.Check for ant trails at the base of stems; if ants are present, control them separately or the aphids will keep returning regardless of what you spray
Frequently Asked Questions
How long does mammoth dill take to grow?▼
Can you grow mammoth dill in containers?▼
Is mammoth dill good for beginners?▼
What does mammoth dill taste like compared to regular dill?▼
When should I plant mammoth dill seeds?▼
How much space does mammoth dill need?▼
Growing Guides from Wind River Greens
Where to Buy Seeds
Sources & References
External authority sources used in compiling this guide.
- ExtensionNC State Extension
- USDAUSDA FoodData Central
See the Methodology page for how this data is sourced, what's AI-assisted, and known limitations.