Mammoth Grey Stripe

Sunflower

90d to harvest

Mammoth Grey Stripe unfurls with a statuesque presence—heads that seem carved from dusk, their petals catching light in soft, smoky tones. The blooms carry bold, slate-edged striping that deepens as the season advances, offering a dramatic, long-lasting show in the garden while producing abundant seed for collectors and growers. Expect sturdy, upright plants with a commanding silhouette that thrives with steady sun and rewards with striking, gallery-worthy flowers.

Crop Dates

Milestone	Date
Start Indoors	Direct Sow
Last Frost	Apr 20th
Transplant / Sow Outdoors	Apr 20th
Harvest Begins	Jul 19th
Harvest Ends	Oct 20th

Crop Details

Trait	Value
Days to Maturity	90
Sun Requirements	Full Sun
Growth Habit	Upright
Support Needed	None
Planting Depth	Normal
Germination Temp (°F)	70
Min Soil Temp (°F)	55
Min Night Temp (°F)	40
Harden Off (days)	Not Required

Recommended Companions

Frequently Asked Questions

What’s the most common disease problem for Helianthus annuus (sunflowers) and how do I manage it?

Look for downy mildew or powdery mildew as white/gray fungal growth on leaves, especially after humid weather. Improve airflow by spacing plants properly, water at the base in the morning, and remove heavily infected leaves early; for repeat outbreaks, use a labeled fungicide compatible with food/ornamentals and follow the label schedule.

How often should I water Helianthus annuus during the main growing phase?

During active growth (roughly the first 6–8 weeks after emergence), keep soil evenly moist but not soggy—aim for deep watering about 1–2 times per week depending on heat and rainfall. Check by pushing a finger 2–3 inches into the soil; water when it’s dry at that depth, since sunflowers dislike constantly wet, cool soil.