Asclepias – Butterfly Milkweed

Growing tips

Germination conditions:

• sowing depth: 5 mm or surface sowing
• optimum germination temperature: 25 to 30ºC
• germination time: 14 to 42 days
• stratification (cold treatment) strongly suggested: press seeds into moistened potting soil, then place the pot wrapped in a clear plastic bag in the fridge for 14 to 30 days. Remove the pot from the bag and germinate under the usual conditions of heat and light. Another technique that works well for stratification is to place the seeds between two sheets of moistened paper towel and slip them into a clear plastic bag (such as a Ziploc) or a clear plastic container. In both cases, it’s important to check every week that the paper towel or potting soil is moist, by spraying it with a spray bottle if necessary. After the stratification period, if you have opted for paper towels, sow the seeds that have germinated in the potting soil. Germination takes an average of 1 month.

When to sow: 3 options

• indoor sowing (after stratification): 8 to 10 weeks before the last frost date in your region, preferably in peat pots to facilitate transplanting and avoid disturbing the roots OR
• direct sowing in spring (after stratification): after last frost OR
• direct sowing in autumn for germination.

Sowing technique: 

• sprinkle the seeds over the soil, then spread them out as evenly as possible so that they don’t overlap.

Transplant outdoors (for seedlings started indoors):

• when there is no longer any risk of frost and after acclimatizing the plants for a few days outdoors.

Distance in the garden:

• between plants: 20 cm
  between rows: 30-50 cm

Plant height: 60-90 cm

Soil: all types of well-drained soil. Once established, plants tolerate drought, but excess water can be a problem.

Exposure: full sun

Flowering: plants flower in midsummer, July and August.

Hardiness zones: 4-9