Does it need a lot of water?

No, it prefers dry to medium soil and is quite drought tolerant once established.

Will it spread aggressively?

It tends to stay in a clump and is not considered invasive.

Plant guide

Green antelopehorn.

Asclepias viridis

Pronounced as-KLEE-pee-as VIR-ih-diss

Also known as antelope-horns, green antelope-horn, green antelopehorn, green antelopehorns, green milkweed, spider milkweed

green antelopehorns — Photo by Cleveland Powell (CC BY) via iNaturalist

The green antelopehorn is a lovely native milkweed that brings charm to any sunny garden. It is a vital host plant for monarch butterflies. You will find it thrives in open, dry areas.

At a glance

Care level: Easy
Plant type: Perennial
Light: Full sun
Indoor light: Direct sun
Water: Every 7 to 14 days
Mature size: 2 feet
Growth rate: Medium
Hardiness: USDA 5 to 9
Bloom time: Late spring to mid summer

Care

Plant this milkweed in a spot that gets plenty of sun and has well draining soil. Watch for aphids on the stems, which are common but usually harmless. Allow the soil to dry out between waterings to keep the roots happy.

Watering: Water deeply once established, but let the soil dry out significantly between sessions.
Feeding: This plant generally does not need fertilizer if grown in decent native soil.
Pruning: Cut back dead foliage in late winter or early spring to make room for new growth.
Repotting: These plants have deep taproots and prefer not to be moved once established.
Soil: Sandy or rocky soil
Soil pH: 6.0 to 7.5
Temperature: -20 to 35°C
Humidity: 20 to 50%
Drought tolerance: High
Lifespan: Perennial, typically 5 to 10 years.
Fragrance: Light
Deer and rabbits: High

Signs it needs repotting

Roots growing out of the drainage holes.
Stunted growth during the active season.

Safety

People: All parts of this plant contain cardiac glycosides which are toxic if ingested.
Pets: This plant contains cardiac glycosides and is toxic to cats and dogs if ingested.
Children: Keep children away from the plant to prevent accidental ingestion of the toxic sap or foliage.
Contact allergens: The milky sap can cause skin irritation or eye inflammation upon contact.
Airborne allergens: There is no significant evidence of respiratory allergies associated with this plant.
Edibility: This plant is toxic and should not be consumed by humans or pets.

How to identify it

Clusters of greenish white flowers
Curved horn shaped seed pods
Lance shaped leaves with wavy edges
Sturdy stems with milky sap

Height: 0.3 to 0.6m
Spread: 0.3 to 0.45m
Leaves: green, deciduous
Flowers: green, purple, white, 2 to 4cm
Fruit: green, brown, Late summer to autumn

Problems to watch for

Aphids · Small insects that cluster on new growth and feed on plant sap.
Milkweed bugs · Insects that feed on the seeds and foliage but rarely kill the plant.

By symptom

Plant problems by symptom

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Growing it

Propagation: seed, division
When to plant: spring, autumn
Overwintering: The foliage will die back to the ground after the first frost. You can leave the stems standing for winter interest or cut them back to the base.
In containers: It can grow in a deep container, but it prefers being planted in the ground due to its long taproot.

Seed

1. Collect mature pods in autumn.
2. Cold stratify seeds in the refrigerator for 30 days.
3. Sow seeds in pots or directly in the garden in early spring.

Plant in groups to create a larger target for butterflies and other pollinators.

Grows well with

Little Bluestem · This grass provides a beautiful textural contrast and shares similar dry soil requirements.
Purple Coneflower · It blooms at a similar time and attracts a wide variety of pollinators to the garden.

Similar species

Common Milkweed · A much more aggressive spreader with larger, fragrant pink flower clusters.
Butterfly Weed · Features bright orange flowers and prefers similar dry, sunny conditions.

Science

Family: Apocynaceae
Genus: Asclepias
Order: Gentianales
Class: Magnoliopsida
Native range: Central and southeastern United States.
Conservation: It is not currently listed as endangered, but it is becoming less common in parts of its native range due to habitat loss.

This plant thrives in dry, rocky prairies and glades where it competes well in poor, well-draining soils.

Value to wildlife: larval host plant, nectar source
Pollinators: bees, butterflies, moths
Uses: pollinator garden, native plant restoration, meadow planting

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 1/9
Soil reaction: 6/9
Light: 8/9
Temperature: 6/9
Moisture: 3/9
Nutrients: 2/9

Taxonomy resolved against GBIF.

Questions people ask

Does it need a lot of water?: No, it prefers dry to medium soil and is quite drought tolerant once established.
Will it spread aggressively?: It tends to stay in a clump and is not considered invasive.

Where the name comes from

The genus name Asclepias honors the Greek god of medicine, while the species name viridis refers to the greenish color of the flowers.

Good to know

It is also known as green antelopehorn milkweed.
The plant relies on specialized pollinators like large bees to navigate its complex flower structure.
It is a critical host plant for monarch butterfly caterpillars.
The seed pods split open to release seeds attached to silky white hairs that catch the wind.

Also in

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This guide was generated with AI on October 19, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.