Whorled Milkweed

Asclepias verticillata

A close up of a small white flower on a green leaf

Whorled Milkweed (Asclepias verticillata) is a perennial native wildflower. Hardy in USDA zones 4 to 9. Prefers full sun.

Sun

Full sun to partial shade

☀️

Zones

4–9

USDA hardiness

🗺️

Height

12-30 inches

📏

Planting Timeline

Zone:

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Transplant

Direct Sow

Transplant

Direct Sow

Showing dates for Whorled Milkweed in USDA Zone 7

All Zone 7 native-wildflower →

Zone Map

Click a state to update dates

Whorled Milkweed · Zones 4–9

What grows well in Zone 7? →

Growing Details

Difficulty

Easy

Spacing18-24 inches

SoilWell-drained, adaptable to sandy, loamy, or rocky soils; tolerates dry conditions

WaterDrought tolerant

SeasonPerennial

ColorPink to light purple

Zone-by-Zone Planting Calendar

Zone	Indoor Start	Transplant	Direct Sow	Harvest
Zone 4	—	June – July	April – June	—
Zone 5	—	May – July	April – June	—
Zone 6	—	May – July	April – June	—
Zone 7	—	May – June	March – May	—
Zone 8	—	April – June	March – May	—
Zone 9	—	March – May	February – April	—

Complete Growing Guide

Light: Full sun (6 or more hours of direct sunlight a day), Partial Shade (Direct sunlight only part of the day, 2-6 hours). Soil: Clay, Loam (Silt), Sand, Shallow Rocky. Drainage: Good Drainage, Moist, Occasionally Dry. Height: 1 ft. 0 in. - 2 ft. 6 in.. Spread: 1 ft. 0 in. - 2 ft. 0 in.. Growth rate: Medium. Maintenance: Medium. Regions: Coastal, Mountains, Piedmont.

Harvesting

3-4 inches long and .5 inch wide smooth, narrow seed pods split open when mature releasing numerous seeds with long tufts of white hair that are dispersed by the wind from September to October

Type: Follicle. Length: 1-3 inches. Width: < 1 inch.

Garden value: Good Dried, Showy

Harvest time: Fall

Storage & Preservation

Whorled Milkweed is primarily grown as a native ornamental and wildflower for pollinator gardens rather than for consumption or harvest. For seed collection and storage, keep dried seedpods in a cool, dry location (50-70°F, 20-30% humidity) in paper envelopes or breathable containers. Seeds can remain viable for 1-2 years when stored this way. To preserve specimens, air-dry seedpods in bundles hung in a well-ventilated space away from direct sunlight for 2-3 weeks until fully brown and papery. Press flowers between absorbent paper for herbarium preservation, or freeze-dry flowers for crafts and arrangements.

History & Origin

Origin: USA, Canada

Advantages

+Attracts: Bees, Butterflies, Pollinators, Songbirds

Considerations

-Toxic (Flowers, Fruits, Leaves, Sap/Juice, Stems): Low severity
-Causes contact dermatitis

Companion Plants

Purple Coneflower (Echinacea purpurea), Black-eyed Susan, and Goldenrod bloom in overlapping windows with whorled milkweed and draw in the same suite of native bees and parasitic wasps — particularly Lysiphlebus testaceipes — that keep oleander aphid numbers from spiraling. Wild Bergamot and New England Aster extend that bloom sequence into October so beneficial insects don't abandon the planting mid-season. Crown Vetch is the one to pull out before it gets started: it spreads by both rhizome and seed, physically outpacing whorled milkweed's slow first-year growth, and Kentucky Bluegrass forms a dense sod mat that cuts off the crown before the taproot can anchor the plant.

Plant Together

Purple Coneflower

Attracts beneficial insects and pollinators, extends bloom season for monarch butterflies

Wild Bergamot

Attracts native bees and butterflies, complementary blooming periods

Little Bluestem

Provides structural support and habitat diversity without competing for nutrients

Black-eyed Susan

Attracts predatory insects that control milkweed pests, similar growing conditions

Wild Lupine

Fixes nitrogen in soil, benefits milkweed growth without direct competition

Butterfly Weed

Another milkweed species that supports monarch reproduction and migration

New England Aster

Provides late-season nectar for monarchs during fall migration

Goldenrod

Attracts beneficial predatory insects and provides late-season monarch nectar

Keep Apart

Crown Vetch

Aggressive spreader that can outcompete and smother native milkweed plants

Kentucky Bluegrass

Dense root system competes heavily for water and nutrients

Tree of Heaven

Releases allelopathic chemicals that inhibit milkweed germination and growth

Troubleshooting Whorled Milkweed

What you'll see, why it happens, and what to do about it.

Stems and leaves coated in a waxy, cottony white residue, usually on new growth

Likely Causes

Oleander aphid (Aphis nerii) — a bright orange-yellow aphid that colonizes milkweeds almost exclusively
Dense plantings that limit natural predator access

What to Do

1.Knock aphids off with a strong stream of water from a hose — repeat every 2-3 days until populations drop
2.Avoid spraying anything, including insecticidal soap; it kills the parasitic wasps (Lysiphlebus testaceipes) that naturally crash aphid populations within 2-3 weeks
3.If the plant is small and heavily colonized, pinch off the worst stems and dispose of them in the trash

Leaves with irregular orange or rust-colored pustules on the undersides, often with yellow blotching on top

Likely Causes

Milkweed rust (Puccinia bartholomaei) — a fungal pathogen specific to Asclepias species
Prolonged wet weather combined with poor air circulation

What to Do

1.Cut affected stems back to the ground — whorled milkweed regrows readily from its root system
2.Space plants at least 18 inches apart to slow spread and improve airflow
3.Bag and trash infected plant material; don't compost it

Seed direct-sown in spring germinates at less than 20%, or not at all

Likely Causes

Skipped cold stratification — Asclepias verticillata seed needs 30 days of moist cold (34-40°F) to break dormancy reliably
Seed buried too deep; small seeds covered more than 1/4 inch often rot before sprouting

What to Do

1.Cold-stratify seed in a damp paper towel inside a sealed bag in the refrigerator for 30 days before sowing
2.Surface-sow or press seed just barely under the soil — no deeper than 1/8 to 1/4 inch
3.Direct sow in fall instead and let winter handle stratification naturally; germination the following spring is usually much stronger

Established plant declines or disappears after the first winter despite surviving dormancy

Likely Causes

Root disturbance — whorled milkweed develops a deep taproot and resents cultivation within 12 inches of the crown
Sod-forming grass competition, particularly from Kentucky Bluegrass or tall fescue smothering the crown before it can push through

What to Do

1.Stop cultivating within 12 inches of the crown once the plant is established — surface mulch is fine, digging is not
2.Clear a 12-18 inch radius of any sod-forming grass around each plant and keep it clear for the first two growing seasons
3.Flag the location in fall — whorled milkweed is one of the last perennials to emerge in spring, often not showing until soil temps reach 60°F, making it easy to assume it's dead and accidentally dig it up

Frequently Asked Questions

Is whorled milkweed a good plant for native wildflower gardens?▼

Yes, whorled milkweed is excellent for native wildflower gardens, especially in zones 4-9. It attracts monarch butterflies and other pollinators, requiring minimal maintenance once established. Being a native perennial, it thrives in appropriate climates without needing intensive care. It's ideal for naturalized landscapes, meadows, and pollinator-focused gardens seeking low-fuss, high-impact natives.

How long does whorled milkweed take to grow from seed?▼

Whorled milkweed germinates slowly, typically within 14-30 days under proper conditions, though germination may extend longer. The plant reaches flowering maturity in its second year, as it's a perennial that establishes roots before producing above-ground growth. Cold stratification (6-8 weeks of moist chilling) often improves germination rates significantly.

Can you grow whorled milkweed in containers?▼

Whorled milkweed can be grown in containers, but it prefers in-ground planting due to its deep taproot system. If containerizing, use deep pots (12+ inches) with well-draining soil. Container plants may require more frequent watering and monitoring. Transplanting to garden soil after the first year typically produces better long-term results and more robust growth.

What spacing should I use when planting whorled milkweed?▼

Plant whorled milkweed 18-24 inches apart to allow mature plants adequate space for full development and air circulation. Closer spacing may result in competition for resources, while wider spacing ensures individual plants can reach their full ornamental potential and support more pollinators.

When should I sow whorled milkweed seeds?▼

Sow whorled milkweed seeds in fall for winter stratification, or in early spring after the last frost. Direct sowing outdoors is effective, as winter cold naturally stratifies seeds. Alternatively, start seeds indoors 8-10 weeks before the last frost, providing 6-8 weeks of cold, moist pre-treatment before sowing.

What are the soil requirements for whorled milkweed?▼

Whorled milkweed is adaptable to various soil types, preferring well-drained soil but tolerating sandy, loamy, or rocky conditions. It succeeds in dry to average soils and actually performs better in leaner conditions. Avoid heavy clay and poorly drained soils that may cause root rot. No significant fertilization is needed once established.