Common milkweed

Questions about common milkweed

Does common milkweed need sun or shade?

Common 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. Once settled in, it stands drought.

What zones does common 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 common milkweed flower in my zone?

In zone 5 it flowers late June to early August. 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 common milkweed be planted?

18 in (45 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 24 in (60 cm), so a group knits into one patch.

It grows 4 ft (120 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.

How many common 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 five in one group.

Is common 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 common milkweed?

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

• Wild quinine: the same job in a bed; 8 in shorter, flowers late June to late August.
• Italian bugloss 'Dropmore': the same job in a bed and the same size; flowers late May to mid July, blue, not pink.
• False sunflower 'Summer Nights': the same job in a bed and the same size; flowers late June to early September, yellow, not pink.

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

Do deer eat common milkweed?

Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.

Will common milkweed spread?

It spreads sideways, by runners or roots; the risk of it taking over is high. Spreads aggressively by underground runners and is hard to remove once established. Plant it only where it can be contained.

What flowers after common milkweed?

Common milkweed is over by early August. These start as it finishes and carry the same spot on, so it never goes flat:

• Big bluestem: from mid August to late September, 6 ft tall (a recorded partner).
• Tiger lily: from late July to late August, 4 ft tall.
• Lilyturf: from early August to mid September, 16 in tall, to stand in front of it and cover its fading stems.

What does common milkweed look like in winter?

Common milkweed dies down, but leave the stems standing: the seed heads stand through the winter, and songbirds eat the seed. Cut them down in early spring, before the new shoots come.

Is common milkweed good for bees and butterflies?

Common milkweed is visited by pollinators, bees, specialist bees, butterflies and songbirds.

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.