Showy milkweed
Asclepias speciosa · Asclepiadaceae
Large, velvety grey leaves and round clusters of starry, pink-and-white flowers with a heavy, sweet scent. The western counterpart of common milkweed.
- Size
- 3½ ft tall, 24 in wide
- Zones
- 3 to 9
- Light
- Full sun
- Flowers
- Mid June to late July
- Pets
- Toxic (moderate)
- Job in a bed
- Drift
A bed built around showy milkweed
The planner designed this bed around showy milkweed when this page was made: a 12 × 6 ft (3.7 × 1.8 m) English border in zone 6, full sun. It chose the other plants from the 966 that suit those conditions, and says below why showy milkweed stands where it does.
The plants
- 1 Showy milkweed × 4, pink
- 2 Sea thrift × 8, white
- 3 Sedum 'Lidakense' × 23, pink
- 4 Brown-eyed Susan × 3, yellow
- 5 Silver sage × 1, silver leaves
- 6 Quaking grass × 3, tan
- 7 Ornamental onion 'Purple Sensation' × 3, purple
- 8 Hyacinth × 8, blue
Why this plant
- The only flat plates. The others are globes, dense clusters, daisies and others. Shape reads at a distance, where colours blur.
Why here
- Anchors a back corner. At 3½ ft it is among the tallest plants here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to brown-eyed Susan (4 ft) and quaking grass (24 in): no two neighbours there are the same height, so the back steps up and down like a skyline.
- 4 plants in 2 groups (3 and 1). Seen again further along, the same plant ties the bed together.
Why now
- In flower for 7 weeks. From mid June to late July.
- Fills a gap. For one of those weeks nothing else on the plan is in flower.
Planned as an English border: 3 of the 6 groups (50%) are drifts, longer along the bed than they are deep. There is more sedum 'Lidakense' than anything else, 23 plants in all. Cool colours (pink, purple and blue) with yellow as the warm note, and white and tan to calm things between them.
The planner's own design check: 12 Excellent, 3 Good, 2 Satisfactory. It flags one thing to watch: Showy milkweed spreads aggressively. Each plant's details say more.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where showy milkweed goes in a border
At 3½ ft it belongs in the middle of a bed. In the planner's ten height classes it is moderately tall (3 to 4 ft).
Its job: drift. Planted in a small group of three or five, and repeated further along in the other number.
A monarch host plant with handsome foliage, but a runner. Give it a wild corner or a meadow, where its colonies can roam, and not a small mixed bed.
- Monarch butterfly gardens
- Meadows and wild corners
- Dry, sunny banks
What to plant with showy milkweed
Plants recorded as good partners for it, and what each pairing does:
- Little bluestem: its blue-green leaves are a setting for the flowers, before and after; fine leaves against its bold ones.
- Wild bergamot: in flower together for four weeks, from early July; medium leaves against its bold ones.
- Blanket flower: in flower together for seven weeks, from mid June; medium leaves against its bold ones; low enough (20 in) to stand in front of it.
Questions about showy milkweed
Does showy milkweed need sun or shade?
Showy milkweed grows in full sun (6 or more hours of direct sun a day).
It wants ordinary well-drained soil, of average fertility, and little watering once settled.
What zones does showy milkweed grow in?
USDA zones 3 to 9. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does showy milkweed flower in my zone?
In zone 5 it flowers mid June to late July. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 3 | Late June to early August |
|---|---|
| Zone 4 | Late June to early August |
| Zone 5 | Mid June to late July |
| Zone 6 | Mid June to late July |
| Zone 7 | Early June to mid July |
| Zone 8 | Early June to mid July |
| Zone 9 | Late May to mid July |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should showy milkweed be planted?
24 in (60 cm) apart, from the middle of one plant to the middle of the next. That is about its full width, so each plant keeps its own outline.
It grows 3½ ft (100 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many showy milkweed plants do I need?
At 24 in apart, set out in staggered rows:
- 3 to fill 10 square feet (about 1 m²)
- 6 for a single row 10 ft (3 m) long
- 10 to fill a 4 × 8 ft bed on its own
In a mixed border, plant it as a group of three or five, with a second group further along in the other number.
In the bed above, the planner used four in two groups.
Is showy milkweed poisonous to dogs and cats?
Yes: moderate toxicity to people, dogs, cats and horses. All parts are poisonous if eaten. The sap can irritate skin and eyes.
Rated from the ASPCA. Where references disagree, the more cautious rating is used.
Is there a pet-safe plant like showy milkweed?
These come closest to doing what showy milkweed does, and no toxicity is recorded for them:
- Spotted bellflower 'Cherry Bells': the same job in a bed, the same flowering time and the same colour; 16 in shorter, 6 in narrower.
- Bee balm: the same job in a bed, the same size and the same colour; flowers early July to early August, medium leaves, not bold.
- Pale purple coneflower: the same job in a bed, the same flowering time and the same colour; 8 in narrower, medium leaves, not bold.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Will showy milkweed spread?
It spreads sideways, by runners or roots; the risk of it taking over is high. Spreads by deep underground stems and comes up some distance from the parent. Best in a meadow or a contained bed.
What flowers after showy milkweed?
Showy milkweed is over by late July. These start as it finishes and carry the same spot on, so it never goes flat:
- Garden phlox: from mid July to early September, 3½ ft tall.
- Lilyturf: from early August to mid September, 16 in tall, to stand in front of it and cover its fading stems.
- Dwarf fountain grass 'Hameln': from late July to mid September, 2½ ft tall, to stand in front of it and cover its fading stems.
What does showy milkweed look like in winter?
Showy milkweed dies down to the ground and there is nothing to see until spring. The old stems can be cut in autumn, or left until spring as shelter for overwintering insects.
More Asclepias
- Butterfly weed Asclepias tuberosa
- Common milkweed Asclepias syriaca
- Purple milkweed Asclepias purpurascens
- Swamp milkweed Asclepias incarnata
- Swamp milkweed 'Ice Ballet' Asclepias incarnata 'Ice Ballet'
- Whorled milkweed Asclepias verticillata
In these guides
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Garden plants native to Canada
- Silver and grey-leaved plants
Zone guides: Zone 3 · Zone 4 · Zone 5 · Zone 6 · Zone 7 · Zone 8 · Zone 9
Every fact on record
- Type
- Perennial
- Size
- 3½ ft (100 cm) tall, 24 in (60 cm) wide
- Plant
- 24 in (60 cm) apart
- Height class
- Moderately tall (3 to 4 ft)
- Place in the bed
- Middle
- Flowers
- Mid June to late July; flat plates; pink
- Leaves
- Bold texture, herbaceous; grey-green
- Shape
- Upright, spreading
- Hardy in
- USDA zones 3 to 9
- Light
- Full sun
- Soil
- Average, well-drained
- Water
- Low
- Feeding
- None needed
- Family
- Asclepiadaceae
Checked against ASPCA poison lists and VASCAN (plants of Canada). Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.