Common milkweed

Sun

Full sun; tolerates light shade but flowers less and may lean.

Water

Water regularly during establishment. Established plants tolerate drought and usually need watering only during prolonged dry spells.

Soil

Well-drained sandy, loamy or clay soil; tolerates poor soil and a broad pH range. Avoid permanently wet ground.

Height

3-5 ft (0.9-1.5 m)

Spread

1-3 ft (0.3-0.9 m) per clump initially; underground stems can form colonies much wider than this.

Flowers

Early to midsummer, with rounded clusters of fragrant, dusty pink to mauve flowers.

Foliage

Large, opposite, oval leaves with prominent veins and softly hairy undersides; stems and leaves release white latex when damaged.

Growth

Fast once established; seedlings may take two or three years to flower.

Care needed

Medium

• Pollinators
• Deer resistant
• Drought tolerant
• Cold hardy
• Heat tolerant
• Wildlife
• Low allergen
• Fragrant

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1 ft (0.3 m)

2. After 1 year

   2.5 ft (0.76 m)

3. After 2 years

   4 ft (1.2 m)

   full size

About 2 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Native to

the US and Canada

Invasive in

the UK

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Plant young plants in full sun where spreading colonies will be welcome; established plants resent moving.
• Water through the first growing season, allowing the surface soil to dry between waterings.
• Do not routinely fertilize; rich feeding can encourage tall, floppy growth.
• Apply a thin mulch to young plantings, keeping it clear of the stems.
• Remove unwanted shoots promptly, digging out their connecting underground stems where practical.
• Wear gloves when handling cut stems and keep the sap away from your eyes.

Pruning. Leave stems and pods through winter where self-seeding is acceptable, then cut dead stems near ground level in late winter or early spring. To limit seedlings, remove pods before they split, checking first for caterpillars and other insects.

Late winter

Cut back old stems before new growth starts; retain some dry stems loosely in a sheltered corner for overwintering insects.

Spring

Plant young plants after the soil is workable and water them in well; mark established clumps because shoots can emerge late.

Late spring

Remove shoots spreading beyond the intended planting area.

Summer

Check for caterpillars before tackling aphids, and water young plants during dry weather.

Late summer

Remove developing pods if you need to prevent self-seeding, or let selected pods mature for seed collection.

Autumn

Sow ripe seed outdoors where cultivation is permitted, allowing winter cold to break dormancy.

• Use in a sunny North American native meadow with little bluestem and black-eyed Susan for summer flowers above a grassy matrix.
• Plant in a generous wildlife border where caterpillar feeding and spreading stems can be accommodated.
• Combine with wild bergamot and purple coneflower for a long summer flowering season and varied flower shapes.
• Grow in a separate naturalistic patch away from small borders, paths and neighbouring gardens.

Garden styles it suits: Native meadow, Wildflower, Wildlife garden, Pollinator garden, New perennial (prairie) and Midwest prairie.

Plant it with: Little bluestem, Black-eyed Susan, Wild bergamot, Purple coneflower, Butterfly weed and New England aster.

Wildlife: A host plant for monarch butterfly caterpillars in North America. Flowers provide nectar for bees, butterflies and other insects; milkweed bugs and several beetles also use the plant. Caterpillar feeding is expected in a wildlife planting and rarely requires treatment.

• Oleander aphids cluster on tender shoots: tolerate small colonies or dislodge them with water after checking for caterpillars; avoid broad-spectrum insecticides.
• Leaf spots and rust can disfigure foliage: improve airflow, water at soil level and remove badly affected fallen leaves.
• Root rot in waterlogged soil: move young plants to a well-drained site rather than trying to maintain them in wet ground.
• Unwanted colonies and seedlings: remove pods before they open and dig out unwanted shoots with their connecting underground stems.

Toxic to people, cats, dogs and horses if eaten. All parts contain cardiac glycosides, including leaves, stems, roots and seeds; ingestion can cause digestive upset and potentially fatal heart disturbances. The milky sap can irritate skin and seriously injure eyes. Do not eat it, and keep it out of grazing areas.

Where it spreads. Spreads aggressively by underground stems and seed, including within its native range in the United States and Canada. Invasive in parts of continental Europe, notably Hungary and neighbouring central European regions. It is an invasive alien species of Union concern in the EU and is regulated in Great Britain, where planting, sale and movement are restricted or prohibited;

• Showy milkweed (Asclepias speciosa)

  Has more conspicuously star-shaped flowers with long, pointed pink hoods and generally woollier, grey-green foliage; common milkweed flowers look rounder and more compact.

• Swamp milkweed (Asclepias incarnata)

  Has much narrower leaves, more branching stems and flatter clusters of pink flowers; it favours moist ground and does not form the same extensive running colonies.

• Hemp dogbane (Apocynum cannabinum)

  Also has opposite leaves and milky sap, but usually branches more freely and bears tiny whitish flowers followed by long, slender paired pods rather than broad, warty milkweed pods.

Asclepias honours Asclepius, the Greek god of medicine, while syriaca means 'of Syria', reflecting an early mistaken association with that region rather than the plant's North American origin.

Propagation. Where legally permitted, sow fresh seed outdoors in autumn, or give seed about 4-6 weeks of cold, moist stratification before spring sowing. Transplant seedlings while small to avoid disturbing their developing roots.

Accepted botanical name

Asclepias syriaca

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Arkansas, Connecticut, Delaware, District of Columbia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Manitoba and Maryland.

Measured

Soil pH 7.5 to 8. Average height 106 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.