Water Amaranth Plant Care

Water Amaranth (Amaranthus cannabinus) belongs to the Amaranthaceae family within the Amaranthus genus. Water Amaranth is native to most of the eastern United States. Water Amaranth is also known as Coastal Water-hemp, American Water-hemp.

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

Leaf size: approximately 4 inches.

Water a young or newly planted Water 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.

Water Amaranth thrives in full sun to partial shade.

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

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

Feed Water 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.

Water Amaranth is suited to USDA Zone 13a.

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.

Water 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 Water 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.

Water Amaranth is frost-tender (hardy to USDA zone 13). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

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

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Water 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.

Water Amaranth grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. Water Amaranth is native to most of the eastern United States. In cooler regions, grow Water Amaranth as a houseplant or bring it indoors before the first frost.