Sunflower Mammoth
Helianthus annuus 'Mammoth'
The classic giant sunflower that creates stunning 12-inch flower heads on towering 12-foot stalks, making it perfect for creating natural privacy screens or dramatic garden backdrops. Children and adults alike are amazed by these impressive blooms that follow the sun throughout the day and produce abundant seeds for wildlife or roasting. This heirloom variety has been delighting gardeners since the 1800s with its reliable performance and impressive size.
Harvest
80-120d
Days to harvest
Sun
Full sun
Zones
2–11
USDA hardiness
Height
1-10 feet
Planting Timeline
Showing dates for Sunflower Mammoth in USDA Zone 7
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Sunflower Mammoth · Zones 2–11
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 3 | April – May | June – July | June – August | — |
| Zone 4 | March – April | June – June | June – July | — |
| Zone 5 | March – April | May – June | May – July | — |
| Zone 6 | March – April | May – June | May – July | — |
| Zone 7 | February – March | April – May | April – June | — |
| Zone 8 | February – March | April – May | April – June | — |
| Zone 9 | January – February | March – April | March – May | — |
| Zone 10 | January – January | February – March | February – April | — |
Complete Growing Guide
Light: Full sun (6 or more hours of direct sunlight a day). Soil: Clay, Loam (Silt), Sand. Drainage: Good Drainage. Height: 1 ft. 6 in. - 10 ft. 0 in.. Spread: 1 ft. 6 in. - 3 ft. 0 in.. Spacing: 12 inches-3 feet. Growth rate: Rapid. Maintenance: Low. Propagation: Seed. Regions: Coastal, Mountains, Piedmont.
Harvesting
Seeds are ovoid and somewhat flattened
Color: Black, Brown/Copper. Type: Achene. Length: < 1 inch. Width: < 1 inch.
Garden value: Edible
Harvest time: Fall
Bloom time: Fall, Summer
Edibility: Seeds are used for cooking oil, livestock feed, and as a snack food or garnish. Petals are edible and young flower buds can be steamed like artichokes.
Storage & Preservation
Fresh sunflower heads should be processed within 24 hours of harvest. Remove seeds by rubbing the head with your hands or using a stiff brush, working over a large bowl. Fresh seeds can be stored in the refrigerator for up to one week in a breathable container.
For long-term storage, air-dry seeds on screens for 2-3 weeks until they contain less than 10% moisture—properly dried seeds will crack rather than dent when bitten. Store completely dry seeds in airtight containers in a cool, dark place for up to one year.
Roasting is the most popular preservation method: soak seeds in salt water for 8 hours, then roast at 300°F for 20-30 minutes until golden. You can also freeze fresh seeds for up to six months, though they'll lose some crunch. Raw seeds can be pressed for oil or ground into sunflower butter, similar to other nut butters.
History & Origin
Origin: Western United States
Advantages
- +Disease resistance: Deer, Drought, Dry Soil, Poor Soil
- +Attracts: Butterflies, Pollinators, Songbirds, Specialized Bees
- +Edible: Seeds are used for cooking oil, livestock feed, and as a snack food or garnish. Petals are edible and young flower buds can be steamed like artichokes.
- +Fast-growing
- +Low maintenance
Companion Plants
Plant Together
Marigolds
Repel aphids, whiteflies, and nematodes while attracting beneficial insects
Nasturtiums
Act as trap crops for aphids and cucumber beetles, protecting sunflowers
Beans
Fix nitrogen in soil while using sunflower stalks for natural support
Cucumbers
Benefit from sunflower shade and wind protection while maximizing garden space
Corn
Similar growing requirements and compatible root systems without competition
Lettuce
Benefits from partial shade provided by tall sunflowers during hot weather
Zinnias
Attract pollinators and beneficial predatory insects while sharing similar care needs
Radishes
Help break up soil around sunflower roots and deter certain pests
Keep Apart
Black Walnut Trees
Produce juglone toxin that severely stunts or kills sunflower growth
Fennel
Releases allelopathic compounds that inhibit sunflower germination and growth
Pole Beans
May climb and overwhelm sunflower stalks, competing for light and nutrients
Nutrition Facts
Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #169270)
Pests & Disease Resistance
Resistance
Generally disease resistant, may get downy mildew in humid conditions
Common Pests
Birds, squirrels, sunflower beetles, cutworms
Diseases
Downy mildew, rust, head rot