Pair of Mammoth Grey Striped Sunflowers stacked with a ruler to show size on a white background.
Very tall Mammoth Grey Sunflowers in front of grey wall with gardener standing next to showing height of plants.
Two Mammoth Grey Striped Sunflowers are held by two gardeners in front of an old cabin.
Grilled Mammoth Grey Striped Sunflower head in a cast iron skillet.
Three Mammoth Grey Striped Sunflower heads on an old metal and wooden background.
Pair of Mammoth Grey Striped Sunflowers stacked with a ruler to show size on a white background.
Very tall Mammoth Grey Sunflowers in front of grey wall with gardener standing next to showing height of plants.
Two Mammoth Grey Striped Sunflowers are held by two gardeners in front of an old cabin.
Grilled Mammoth Grey Striped Sunflower head in a cast iron skillet.
Three Mammoth Grey Striped Sunflower heads on an old metal and wooden background.

Sunflower Seeds,
Mammoth Grey Striped

4.336 ReviewsSKU: #FL735
Price
Regular price $3.00
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Min. 25 seeds

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Description

(Helianthus annuus). The standard giant variety that produces delicious seeds. The 10-foot plants produce heads that average 12 inches across. A stately garden plant.

Plant Details

Botanical Name
Helianthus annuus
Life Cycle
Annual
Sun Requirement
8–12 hr.
Days to Germinate
7–14
Days to Maturity
90–100
Planting Depth
½ in.
Plant Spacing
18–24 in.
Ideal Temperature
65–75°F
Frost Hardy
No

Growing Guide

When to Grow

Direct sow Mammoth Grey Striped sunflower seeds after the danger of the last frost has passed, when soil temperatures are above 60 F. In most areas, this is typically in late spring. You can also start indoors 2-3 weeks before the last frost, and carefully transplant seedlings afterwards. If you’re not sure how to find your first and last frost dates, consult our blog post 'Our Experts Answer Questions, Share Resources.'

How to Sow and Plant

Plant seeds 1/2 inch deep and space them 18-24 inches apart for maximum growth. Ensure the soil is well draining and rich in organic matter like compost. Once planted, water thoroughly to help the seeds settle, and thin seedlings to one plant per spot after germination​.

How to Grow

Make sure that the plants get at least 8 hours of sun daily. Water deeply but infrequently, letting the soil dry between waterings to encourage strong root development. Mammoth sunflowers are heavy feeders, so mix compost or a slow-release fertilizer into the soil at planting time. Taller plants may need staking, especially in windy areas​.

How to Save Seeds

  • When petals die back and heads begin to dry and turn brown, place a paper bag over the heads to protect seeds from birds.
  • After a few days, the heads will dry to a dark brown. Bring the heads indoors and hang them upside down in a dry area in direct sunlight for up to a week, shaking seeds free each day.
  • Store seeds in a cool, dark, dry place.

FAQ

Do Mammoth Grey Striped sunflowers need support?

Yes, due to their height and heavy heads, staking may be necessary in windy areas.

How often should I water Mammoth Grey Striped sunflowers?

Water deeply but let the soil dry between waterings. Once established, they are drought-tolerant.

Can I grow Mammoth Grey Striped in poor soil?

While sunflowers can tolerate various soils, they grow best in rich, fertile soil with good drainage.

Browse our full range of sunflower seeds.

Customer reviews

4.3 / 5 36 Reviews

What gardeners are saying

  • Truly mammoth: Stalks of 10 to 15 feet with heads a foot or more across.

  • Bees and birds flock: Covered in bees in bloom, then birds and squirrels in the fall.

  • Seeds by the thousands: Big plump seeds, tasty roasted, with plenty left for wildlife.

  • Easy and fast: Nearly every seed sprouts and shoots up; kids love watching.

  • Heads up: Heavy heads need staking; crowded or shaded plants stay small.

More to grow!
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