Helianthus annuus 'Mammoth Grey Stripe'
This giant selection of the common sunflower is grown for towering stems and very large seed heads. Plants are usually single stemmed with one main flower. The form stands out for height and seed yield. It performs best with long, warm summers in full sun. It is grown as an annual across North America. Gardeners grow it at the back of borders or as seasonal screens. Birds take ripening seeds readily.
At‑a‑glance
- Group/Class: Annual sunflower cultivar
- Height × spread: 8-12 ft × 2-3 ft (2.4-3.6 m × 0.6-0.9 m)
- Bloom window: mid summer to early fall
- Color & flower form: single large golden yellow ray florets with dark disk; 8-12 in heads (20-30 cm)
- Fragrance: 0 none
- USDA hardiness: grown as annual in all USDA zones
- Breeder / Year / Origin: unknown
- Cut‑flower notes: thick stems; best cut just as rays lift; typical vase life 6-12 days in clean water depending on cultivar and care
- Pet safety: safe
How it differs
- Taller than most garden sunflowers
- Usually single headed rather than freely branching
- Produces heavy edible seed heads
- Makes a seasonal screen rather than a bouquet crop
Strengths
- Impressive height and flower size
- Good seed production for wildlife and roasting
- Heat tolerant with adequate moisture
Care in one minute
- Site: full sun with wind protection where possible
- Soil: well‑drained soil with a slightly acidic pH of 6.0 to 6.8; loosen deeply for strong taproots
- Water: deep, regular watering during dry spells
- Feeding: avoid high nitrogen to limit floppy growth
- Pruning: do not pinch single‑stem types
- Overwintering: not applicable; warm‑season annual in North America
Watch‑outs
- Can lean or flop in wind without staking
- Birds and squirrels may damage maturing heads
- Needs ample space and sun
Best uses (tags)
cutting, screens, back borders, wildlife, kids’ gardens
Provenance note
An old grey‑striped seed form widely sold in North America; exact breeder and introduction date are not verified.
References
- USDA NRCS Plant Guide: Annual Sunflower
- Texas Master Gardeners: Sunflower ‘Mammoth’
- UMN Extension: Sunflowers
- ASPCA: Sunflower non‑toxic to pets
Written by: Your Flowers Guide editorial team
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