How to Grow Mammoth Red Rock Amaranth
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Mammoth Red Rock Amaranth
Amaranthus cruentus
vegetableMammoth Red Rock is a large, ornamental grain amaranth variety prized for its deep crimson seed heads and nutritious grain. The plant produces impressive burgundy-red plumes that can reach 12-18 inches long and contains protein-rich seeds. It serves dual purposes as both a decorative garden plant and a productive grain crop.
When should you plant Mammoth Red Rock Amaranth in your zone?
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Example Mammoth Red Rock Amaranth timeline · Pittsburgh, PA (Zone 6b)
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Plant Mammoth Red Rock Amaranth
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Mammoth Red Rock Amaranth
Around Jul 16≈ 90 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Mammoth Red Rock Amaranth dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 4-10; performs best in zones 6-9 with warm growing seasons
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Get my Mammoth Red Rock Amaranth timeline →Growth Stages
Seedling
2-3 weeksTiny plants with 2-4 true leaves, cotyledons visible. Plants are 2-4 inches tall.
Keep soil consistently moist but not waterlogged. Thin seedlings to proper spacing once they have 2-3 true leaves. Provide bright light to prevent leggy growth.
Vegetative Growth
3-4 weeksRapid stem elongation with increasing leaf size. Plants develop deep green to reddish foliage, reaching 12-24 inches tall. Strong root system establishes.
Ensure consistent spacing and adequate sunlight. Monitor for pests. Water regularly during dry spells. Side-dress with compost or balanced fertilizer if growth appears slow.
Flowering/Panicle Formation
3-4 weeksTerminal flower panicle (seed head) begins to emerge from the top of the plant, initially green then transitioning to deep crimson-red. Plant height reaches 36-48 inches or more.
Reduce nitrogen fertilization to redirect energy toward seed production. Continue moderate watering but allow soil to dry slightly between waterings. Support tall plants if winds are strong.
Seed Development & Maturation
3-4 weeksPanicle becomes fully colored deep red/burgundy, 12-18 inches long. Seeds fill out within the flowers. Foliage may yellow or brown as plant directs energy to seeds.
Reduce watering significantly; allow plant to dry down naturally. Do not fertilize at this stage. Pest pressure typically decreases as plant senesces.
Harvest Ready
Ready to harvestSeed head is fully mature, deep crimson, and seeds are hard and difficult to remove by hand. Leaves may be mostly brown; entire plant may appear dried.
Cut panicles when seeds no longer rub off easily but before complete seed drop. Hang to dry in a well-ventilated area for 2-3 weeks before threshing. Store seeds in cool, dry conditions.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Row covers on seedlings, neem oil spray, diatomaceous earth, or companion planting with radishes
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Hand-pick or use Bacillus thuringiensis (Bt) spray; encourage native predators
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Strong water spray, neem oil, or miticide if severe; improve air circulation
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Insecticidal soap, neem oil, or release of ladybugs; early detection is key
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and
Beer traps, diatomaceous earth barriers, hand-picking at dawn/dusk, or copper tape
Uses
Nutritious Grain & Flour
CulinaryAmaranth seeds are gluten-free and exceptionally high in protein, fiber, and minerals. They can be popped like popcorn, cooked as a grain similar to quinoa, or ground into nutrient-dense flour for baking. [source]
Edible Leaves
CulinaryYoung leaves and tender shoots are edible as spinach-like greens, rich in vitamins A and C. Harvest leaves regularly to encourage bushier growth, though this will reduce seed production. [source]
Traditional Herbal Use
MedicinalAmaranth has been used in traditional medicine for anti-inflammatory and antioxidant properties. Seeds and leaves contain compounds studied for potential cardiovascular and digestive health benefits. [source]
Natural Dyes
HouseholdThe deep red pigments in Mammoth Red Rock can be extracted and used as a natural dye for textiles and crafts, producing burgundy to deep red hues. [source]
Bird & Pollinator Feed
WildlifeMature seed heads left standing in the garden provide food for finches, sparrows, and other seed-eating birds throughout fall and winter. Flowers attract pollinators during bloom. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Harvest panicles when seeds are hard and fully colored (deep red/burgundy). Cut the entire seed head with 6-12 inches of stem attached, leaving the rest of the plant standing. Hang upside down in a warm, dry, well-ventilated location for 2-4 weeks. Once completely dry, thresh by rubbing the panicle between hands over a bucket or fine mesh to separate seeds from chaff. Store seeds in a cool, dry place in airtight containers; they remain viable for 3-5 years.
Fun Facts
- 🌱 Mammoth Red Rock amaranth was an important staple grain for the Aztecs and other ancient Mesoamerican civilizations, prized for both its nutritional and ceremonial significance.
- 🌱 Amaranth is technically a pseudocereal—not a true grain—making it an excellent gluten-free alternative that contains all nine essential amino acids, rivaling the protein content of quinoa.
- 🌱 A single mature Mammoth Red Rock plant can produce up to 250,000 tiny seeds from one flowering panicle, making it an incredibly prolific grain crop for home gardeners.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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