Mammoth Grey Stripe
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
Growing note: In frost-free Zone 11b, grow this cool-season crop during the cooler dry season (October–February).
| Milestone | Date |
|---|---|
| Start Indoors | — |
| Climate | Frost-Free Climate |
| Transplant / Sow Outdoors | Oct 1st |
| Harvest Begins | Dec 30th |
| Harvest Ends | Feb 28th |
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 can I tell when Helianthus annuus ‘Mammoth Grey Stripe’ is ready to harvest?
Harvest when the back of the flower head turns yellow to tan and the outer petals start to fall, while the developing seeds in the head look plump and filled out. If you rub a seed gently with your thumb, it should feel firm and come off cleanly; most crops are ready around ~90 days from sowing.