Milkweed Growing Guide

Asclepias syriaca, Asclepias incarnatum

Milkweed

Crop Rotation Group

Miscellaneous ●

Soil

Fertile, well-drained soil.

Position

Full sun to partial afternoon shade.

Frost tolerant

Milkweed is a hardy perennial, tolerating winter cold to -34°C (-30°F).

Feeding

None needed.

Spacing

Single Plants: 60cm (1' 11") each way (minimum)
Rows: 60cm (1' 11") with 60cm (1' 11") row gap (minimum)

Sow and Plant

Sow seeds of common milkweed where you want the plants to grow in autumn or early spring, barely covering them with soil. If you get only one or two plants, you will have a good start on a milkweed patch. You also can start with a container-grown plant from a nursery, which is the only way to grow improved cultivars of swamp milkweed such as rose pink ‘Cinderella’ or white ‘Ice Ballet’, which bloom longer and stronger than the wild species. Young plants need water their first year, but after that common milkweed is quite drought tolerant. Swamp milkweed grows best with regular water.
Our Garden Planner can produce a personalised calendar of when to sow, plant and harvest for your area.

Notes

Common milkweed bears globes of intricate flowers that are favourites of bees and butterflies. It is a fast spreader, with new plants rising from deep wandering rhizomes. Common milkweed is too coarse and thuggish for most flower gardens, but not swamp milkweed (A. incarnata), which grows into a well-behaved clump. Milkweeds are rarely bothered by deer. Milkweeds are native American plants. Common milkweed may form large colonies in wildflower meadows. Swamp milkweed is best suited to moist sites or stream banks, its natural habitat.

Harvesting

Gather stems of swamp milkweed for use in cut arrangements as you need them. Set cut blossoms outdoors for a short time to allow small insects to escape. Some people are allergic to milkweed sap, which also should be avoided because it is so sticky. Topping back milkweed plants in early summer extends the bloom period.

Troubleshooting

Most gardeners are happy to see milkweed leaves being devoured by monarch caterpillars, and not so pleased with bristly tussock moth caterpillars, which should not be touched. Bright yellow milkweed aphids can appear in large numbers on growing tips, and they are only moderately discouraged by a spray of water. Pinch off badly infested branches and compost them. Collect colourful orange and black milkweed bugs by knocking them into a container of soapy water.

Planting and Harvesting Calendar

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Pests which Affect Milkweed