Botanical Interests
Mammoth Sunflower
Mammoth Sunflower
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Product Details
Product Details
This giant among sunflowers is a fast grower whose single stalk can reach 12' tall and produces one 10"-12" flower! Not fussy about soil, it's very easy to grow and drought tolerant. Grow in a tight row to make an attractive screen. Sow monthly for continual bloom.
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- Variety Info
- Sowing Info
- Growing Info
Variety Info
Family: Asteraceae
Type: Sunflower (Learn more)
Native: North America
Hardiness: Annual
Exposure: Full sun
Bloom Period: Summer to frost
Plant Dimensions: 6'–12' tall
Variety Info: Up to 12"-wide flowers with yellow petals and a brown center. Single type.
Attributes: Attracts Pollinators, Cut Flower, Drought Tolerant, Heat Tolerant, Edible Flower
Sowing Info
When to Sow Outside: RECOMMENDED. 1 to 2 weeks after your average last frost date.
When to Start Inside: 2 to 4 weeks before your average last frost date. Sunflowers are senstive to root disturbance; sow in biodegradable pots that can be planted directly in the ground.
Days to Emerge: 10–15 days
Seed Depth: ¼"–½"
Seed Spacing: A group of 3 seeds every 24"
Thinning: When 3" tall, thin to 1 every 24"
Growing Info
Harvesting: Seeds are ready to harvest when the back of the head has dried and turned brown, about 4 weeks after the flowers have been pollinated. Petals will have wilted and fallen off, and the seeds will be plump, and colored white with gray/black stripes. Seeds ripen around the outside of the flower first; the ones in the center will ripen last. Average yield is approximately 1 pound per head.
- Chandi C.Verified BuyerRated 5 out of 5 starsDec 21, 2025Great Seeds
Wow. I did an experiment to see if I could grow these in good soil and in awful soil and these little seeds took to both. I have one flower that is about 5 feet tall and many more still growing. So fun and easy.
Which best describes you as a gardener? BeginnerEGEpic GardeningDec 22, 2025Hey Chandi,
Thank you so much for taking the time to share your awesome experiment with our Mammoth Sunflower seeds! We're absolutely thrilled to hear that these tough little seeds performed so well in both good and awful soil - that's exactly the kind of resilience we love to see! A 5-foot tall sunflower with many more still growing sounds incredible! We love that you found them so fun and easy to grow. Thank you for choosing us and for sharing your growing success with us. Keep on growing 🌻️
- Ryan 🌱Verified BuyerRated 5 out of 5 starsDec 20, 2025Impressive and fun 🌻
Every seed I've planted has sprouted. Outdoors, just miracle grow, easy. The bigger the pot the bigger the flower! They make tons of roots and they're thirsty. They bring so much joy every day 🌻
Which best describes you as a gardener? BeginnerEGEpic GardeningDec 22, 2025Hey Ryan,
Thank you so much for taking the time to share your amazing experience with our Mammoth Sunflowers! We're absolutely thrilled to hear that every single seed sprouted for you - that's incredible! Your tip about the bigger pot leading to bigger flowers is spot on, and we love that you discovered how thirsty these beauties can get with all those roots. There's nothing better than hearing that our sunflowers are bringing you joy every single day! Thank you for choosing us and for sharing your growing success with us. Keep on growing 🌻️
- Mary O.Verified BuyerRated 5 out of 5 starsNov 6, 20245 Stars
I planted five, and as you can see all five grew. I think they would be taller except I didn’t get them transplanted soon enough, and I also didn’t choose a sunny enough location. I am still thrilled that they all grew and they all have flowers coming! I will be planting them again next year, just in a different location and probably directly in the garden.
- Erle R.Verified BuyerRated 5 out of 5 starsAug 3, 20245 Stars
It was very easy I’m 15 and this is my first gardening season and just put these in the ground and watched them grow. Did plant these in front of my peppers which is my mistake but these are growing very well.
- Tanya S.Rated 5 out of 5 starsJun 4, 20245 Stars
This is my first time growing these. Oh what fun! They are close to if not about 10 feet tall. I can't wait to harvest the seeds.
Which best describes you as a gardener? Intermediate
