Purple milkweed

Questions about purple milkweed

Does purple milkweed need sun or shade?

Purple milkweed grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).

It wants ordinary well-drained soil, of average fertility, and a good soak in dry spells. Once settled in, it stands drought.

What zones does purple milkweed grow in?

USDA zones 3 to 8. It is hardy to zone 3, which means it survives winter nights down to about −30 °F (−34 °C).

Above zone 8 it struggles: the zones measure winter cold, but a plant's top zone usually means the summers are too hot or the winters too mild for it to rest.

Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.

When does purple milkweed flower in my zone?

In zone 5 it flowers early June to mid July. As a summer flower it moves about half a week for every zone: earlier where it is warmer.

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 purple milkweed be planted?

18 in (45 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 3 ft (90 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many purple milkweed plants do I need?

At 18 in apart, set out in staggered rows:

• 5 to fill 10 square feet (about 1 m²)
• 7 for a single row 10 ft (3 m) long
• 17 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 three in one group.

Is purple 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 NC State Extension and the ASPCA. Where references disagree, the more cautious rating is used.

Is there a pet-safe plant like purple milkweed?

These come closest to doing what purple milkweed does, and no toxicity is recorded for them:

• Meadow sage: the same job in a bed, the same flowering time and the same colour; 12 in shorter, medium leaves, not bold.
• Purple coneflower: the same job in a bed, the same size and the same colour; flowers late June to early September, medium leaves, not bold.
• Anise hyssop: the same job in a bed and the same size; flowers early July to early September, lavender, not purple.

Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.

Do deer eat purple milkweed?

They may. NC State does not list it as resistant to deer or rabbits. Where they visit, protect it, or plant it among ones they avoid.

What flowers after purple milkweed?

Purple milkweed is over by mid July. These start as it finishes and carry the same spot on, so it never goes flat:

• Wild bergamot: from early July to late August, 3½ ft tall (a recorded partner).
• Black-eyed Susan: from mid July to mid September, 24 in tall, to stand in front of it and cover its fading stems.
• Lilyturf: from early August to mid September, 16 in tall, to stand in front of it and cover its fading stems.

What does purple milkweed look like in winter?

Purple 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.

Is purple milkweed good for bees and butterflies?

Purple milkweed is visited by pollinators, bees, butterflies and hummingbirds.

It is a host plant: the caterpillars of monarch (at risk) and milkweed tussock moth feed on its leaves. A butterfly can only lay its eggs on its host plants, so these do more for it than any nectar flower.

It is native to the United States and Canada.