Amaranthus retroflexus

Redroot Pigweed Identification & Control

Redroot Pigweed is an exceptionally aggressive, highly prolific summer annual broadleaf weed in the amaranth family. Native to tropical America but thoroughly naturalized globally, it is a severe agricultural and garden pest. Growing up to 6 feet tall, it features a highly distinctive, bright pink-to-red fleshy taproot. It is a legendary seed producer, with a single robust plant capable of producing up to 100,000 to 200,000 seeds, aggressively robbing soil nitrogen and outcompeting crops.

Sunlight Full Sun

Watering Tolerance Low to Moderate

Soil Adaptability Rich / High Nitrogen / Sandy Loam

Growth Temp 15°C - 42°C

Danger / Toxicity Pet Toxic / High Nitrates

Botanical macro photography of Redroot Pigweed (Amaranthus retroflexus) - Plant AI care and control database

How to Identify Redroot Pigweed

An erect annual with rough, hairy stems, egg-shaped dull-green leaves, a brilliant red or pink fleshy taproot, and dense, bristly green flower spikes.

✔
Silky Pink-Red Taproot: The central taproot and lower stem base are colored a highly distinct, brilliant pinkish-red to bright rose-purple.
✔
Rough Hairy Stems: Stems are stout, branched, and densely covered in short, stiff, rough hairs, growing up to 6 feet tall.
✔
Bristly Green Flower Spikes: Tiny green flowers are clustered in exceptionally dense, stiff, prickly, bristly spikes at the top of stems.

⚠️ Pet & Livestock Warning: Redroot Pigweed actively accumulates toxic levels of **nitrates** from agricultural fertilizers! If consumed in large quantities by pigs, sheep, or cattle, it causes fatal nitrate poisoning and kidney failure (pigweed toxicosis).

Complete Care & Management Guide

Access highly technical, scientific management directives to control or cultivate Redroot Pigweed effectively.

Highly drought-tolerant once established due to its strong, fleshy taproot that taps deep sub-soil moisture. It thrives during hot, dry summer baking that wilts garden crops.

Controlled moderately by early cutting. Pruning before the bristly green spikes flower prevents seed production, breaking its annual life cycle. Snapped plants will quickly sprout lateral flower shoots.

An extreme nitrogen hoarder. It actively absorbs high levels of soil nitrates, starving nearby vegetable crops. Avoid over-fertilizing infested beds.

Requires Full Sun. It cannot tolerate shade and will fail to germinate or survive under a dense forest canopy or beneath thick garden shrub shading.

Thrives in rich, highly fertile, tilled agricultural loam and high-nitrogen garden beds. It struggles in extremely sterile, wet sandy bogs.

Reproduces strictly by seeds. A single plant can produce up to 200,000 tiny, shiny black seeds that can remain viable in the soil for over 30 years.

A summer annual. Germinates in late spring when soil temperatures reach 65°F (18°C). The entire plant is completely killed by the first winter freeze, leaving seeds.

Features a shallow but extremely tough, fibrous root system anchored to a strong, distinctive pink-red fleshy taproot. It is very easy to pull out when young.

Occasionally targeted by pigweed weevils and flea beetles, though insect pressure rarely slows its aggressive agricultural invasion.

Subject to **Bacterial Leaf Spot** and **Downy Mildew** in damp autumns, though diseases rarely kill the plant before it successfully drops seeds.

To control Redroot Pigweed organically, hand-pull young rosettes in early summer before they develop their tough, woody red taproot and bristly seed spikes, and mulch heavily.

Common Diseases & Treatment

Nitrate Toxicity Accumulation

Symptoms: Symptoms: Leaves accumulate high levels of chemical nitrates, becoming dark-green and extremely toxic to grazing pets.

Action: Action: Hand-weed and discard immediately. Avoid using synthetic nitrogen fertilizers on weed-prone vegetable margins.

Late-Season Stolon Branching

Symptoms: Symptoms: Cut pigweed stems quickly grow low, horizontal lateral branches that produce seeds despite mowing.

Action: Action: Decapitate the root crown. Use a sharp hoe to slice the red taproot 1 inch below the soil surface to kill the plant permanently.

Frequently Asked Questions

Why is it called 'Redroot' Pigweed?

It is named 'Redroot' because the plant's lower stem and central fleshy taproot are colored a highly distinct, brilliant rose-purple or reddish-pink, which makes it incredibly easy to identify when pulled from the ground.

Are the seeds edible?

Yes! Redroot Pigweed belongs to the amaranth family. Historically, Native Americans harvested the abundant tiny black seeds to grind into a highly nutritious, protein-rich flour, and the young tender spring leaves are edible cooked.

Is Redroot Pigweed toxic to dogs?

Yes, if eaten in large quantities. The plant accumulates high levels of nitrates and soluble oxalates, which can cause gastrointestinal distress, weakness, and potential kidney failure in curious pets.

What is the best way to prevent it organically?

Because it is a summer annual that germinates from seed in warm soils, applying 3 inches of organic wood mulch or straw in late spring completely blocks light from reaching the dormant seeds, preventing germination.