Redroot Pigweed
Amaranthus retroflexus
An erect, annual herb with dull green, egg-shaped leaves and a rough, hairy stem often tinged with red toward the base. It features compact, bristly green flower spikes.
- Light
- Full sun (6+ hours per day); it is a C4 plant that thrives in high heat and intense light.
- Water
- Moderate; highly drought-tolerant once established but grows more vigorously with regular moisture. Avoid waterlogging.
- Growth
- Summer annual with an upright growth form, typically reaching 1 to 3 feet in height, though it can grow taller in optimal conditions.
Care instructions
As a prolific weed, it requires little care. It thrives in disturbed soils with full sun and moderate moisture, but can survive in poor, dry conditions. No fertilization is needed.
Growing details
Sunlight
Full sun (6+ hours per day); it is a C4 plant that thrives in high heat and intense light.
Watering
Moderate; highly drought-tolerant once established but grows more vigorously with regular moisture. Avoid waterlogging.
Soil
Prefers nitrogen-rich, well-draining loamy soils with a pH of 5.5 to 8.0.
Hardiness zone
Annual; grows in USDA zones 2-11 during frost-free months.
Growth habit
Summer annual with an upright growth form, typically reaching 1 to 3 feet in height, though it can grow taller in optimal conditions.
Bloom season
Mid-summer to early autumn; flowers are small, green, and clustered in dense, terminal bristly panicles.
Propagation
Propagates solely by seed; a single plant can produce over 100,000 tiny black seeds that remain viable for decades.
Common pests & issues
Susceptible to aphids and flea beetles. Often hosts viruses that affect commercial crops like beets and spinach.
Similar species
Amaranthus hybridus (Smooth Pigweed) which has smoother stems and less bristly flower spikes, and Chenopodium album (Lambsquarters) which has mealy, triangular leaves.