annual

Spiny Amaranth

The Story

Plant Bio

Amaranthus spinosus is an erect, branching summer annual herb native to tropical and subtropical regions of the Americas. It features alternate, ovate to lanceolate green leaves with dull undersides and sharp, paired spines at the base of each leaf petiole.

This species is distinguished by its rigid nodal spines and its dual flowering structure, which consists of dense axillary clusters and long, slender terminal panicles. The greenish flowers produce prolific seeds that germinate rapidly in warm, disturbed soils.

Uses & Benefits:

Provides structural interest with its erect branching habit and long, slender terminal flower spikes.

Serves as a botanical specimen for studying spiny plant adaptations and amaranth morphology.

Seeds provide a food source for ground-feeding granivorous birds and small mammals.

Essentials

At a Glance

Plant Type

Annual

Height

40"

Width

24"

Light

Full Sun

Zones

4, 5, 6, 7, 8, 9, 10

Water

Low

Humidity

High

Lifespan

Annual

Native To

Americas

Toxicity

Toxic to Livestock

Bloom period

Summer – Fall

In flower about 6 months of the year

Planting

How to Grow

Sow seeds directly into warm, disturbed soil in a location receiving full sun after all danger of frost has passed.
Water lightly to keep the soil moist until germination occurs, which happens rapidly in warm temperatures.
Allow the soil to dry between waterings once established, as the plant possesses high drought tolerance.
Monitor the plant closely and hand-pull or deadhead before seed set to prevent unwanted spreading.

Pro Tip

Wear heavy leather gloves when working near this plant to avoid painful punctures from the rigid nodal spines. To prevent aggressive self-sowing, cut back the terminal flowering spikes before they transition from green to seed.

Keep It Thriving

Care Guide

Do

Wear heavy leather gloves when handling the plant to protect against the sharp, rigid nodal spines.
Grow in full sun and well-drained soil to ensure strong, upright growth.
Remove spent flowering spikes early in the season to control self-seeding.

Don't

Do not apply high-nitrogen fertilizers, as this encourages excessive, weak vegetative growth.
Do not allow livestock to graze heavily on the foliage, as it can accumulate toxic levels of nitrates and oxalates.
Do not plant near pastures or cultivated fields where it can easily escape and become an invasive weed.

Seasonal Care Calendar

Task	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Deadhead
Pest Check
Plant
Spring Cleanup

Watch Out For

Pests & Diseases

Common Pests

Common Diseases

In the Garden

Landscape Uses & Companions

Landscape Uses

Wild and Naturalistic GardensSpecialized Botanical Collections

Companion Plants

Celosia argentea Gomphrena globosa

Multiply

Propagation Methods

Good to Know

Common Questions

Spiny Amaranth questions

What zones can Spiny Amaranth grow in?

Spiny Amaranth is hardy in USDA Zones 4–10. Inside that range it survives winter in the ground; outside it, grow it as an annual or a container plant you protect.

When does Spiny Amaranth bloom?

Spiny Amaranth typically blooms in summer through fall. Exact timing shifts a week or two with your zone — Sow's bloom calendar maps it to your garden.

Does Spiny Amaranth need full sun?

Spiny Amaranth does best in full sun (6+ hours).

Is Spiny Amaranth drought tolerant?

Yes — once established (usually after the first full season), Spiny Amaranth handles dry spells with minimal watering. Water deeply its first year to build the root system that makes that possible.