Spiny Amaranth Plant Care

Spiny Amaranth (Amaranthus spinosus) belongs to the Amaranthaceae family within the Amaranthus genus. Spiny Amaranth is native to the tropical Americas. Spiny Amaranth is also known as Prickly Amaranth, Thorny Amaranth.

Spiny Amaranth displays an upright, bushy growth habit, reaching up to 4 ft tall with a spread of approximately 2 ft. Spiny Amaranth produces small, inconspicuous flowers in dense clusters.

Leaf size: approximately 4 inches.

Water a young or newly planted Spiny Amaranth every 7–10 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established shrubs mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

Spiny Amaranth thrives in full sun to partial shade.

Amaranthus spinosus tolerates temperatures of 60–85°F. Spiny Amaranth prefers humidity levels of 40–70%.

Well-draining soil with high organic content. Good drainage is essential for Spiny Amaranth to prevent waterlogging, which leads to root rot and fungal issues.

Feed Spiny Amaranth every 4 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established shrubs in good soil often need little extra feeding, so let weak growth or pale foliage guide you.

Stop feeding by late summer so new growth can harden before winter.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Choose a spot with full sun to partial shade and well-draining soil with high organic content. Avoid low spots where water collects after rain.

Spiny Amaranth is suited to USDA Zone 8a – 11b.

Plant container-grown or balled-and-burlapped shrubs in spring or early autumn, setting the root flare at soil level, and water well after planting.

Spiny Amaranth can spread to about 2 ft (0.6 m) and reach about 4 ft (1 m) tall. Space plants about 2 ft (0.6 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the plant spacing calculator.

Prune Spiny Amaranth while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.

If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the shrub in one year.

Spiny Amaranth is hardy down to USDA zone 8a, so once established it can stay outdoors through winter in that zone and warmer ones.

Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.

Young and container-grown shrubs need extra protection: roots in a pot freeze much more easily than roots in the ground.

Spiny Amaranth can be propagated through seeds, stem cuttings. Similar propagation techniques also apply to southern amaranth plant care, which shares the same genus.

See all plants toxic to cats and plants toxic to dogs.

Spiny Amaranth is susceptible to aphids, spider mites. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.

Spiny Amaranth grows outdoors in USDA Zone 8a – 11b. It survives winters down to planting zone 8a. Spiny Amaranth is native to the tropical Americas.