An amazing giant heirloom sunflower with enormous blooms, up to 1 ft. across. The large yellow flowers with brown centers top plants 9-12 ft. tall and yield heavy loads of seeds. Fast and easy to grow, Mammoth sunflowers are great for creating a sunforest for kids, a tall annual hedge or screen.
- Taxonomy: Helianthus annuus
- Package size: 10 seeds per packet
- Seed Type: Annual
- Sow Indoors or Outdoors: Mammoth sunflower seeds are recommended solely for outdoor growth because of their 9 – 12′ height. Plants grow so vigorously that there is little reason to start seed indoors. Sow directly after final frost in a sunny spot on the north end of the garden and sheltered from strong winds. Sunflowers may need staking if plants are grown isolated.
- Days to Maturity: 90 – 110 days
- Hardiness Zone: 2 – 11
- Planting Depth: Plant 2 – 3 seeds ½” deep
- Plant Spacing: 18″
- Growth Habit: 108 – 144” tall bushy upright with 36 – 40” spread and huge 12” head
- Soil Preference: Organic, nutrient-rich, well-drained
- Light Preference: Full sun
- Diseases/Pests/Troubleshooting: Always plant tall varieties of sunflowers on the north end of a garden. Mammoth sunflowers are one of the most resilient and fastest growing flowers, and will not take long to shadow an entire garden if not properly planned. Mammoth sunflowers are susceptible to leaf fungal spots, rust, and powdery mildew. Monitor regularly for caterpillars and beetles feeding on the foliage.
- Colour: Bright yellow sunburst petals with deep yellow-orange seeds
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