How to Germinate Milkweeds

by

MANY MILKWEEDS (Asclepias spp.) are notoriously difficult to germinate. But don’t despair. The Wildflower Center has developed and tested a protocol that results in good germination rates for a number of our native milkweed species. Follow this process and you’ll soon be on your way to supporting monarchs, bumblebees and tons of other insects that depend on milkweed plants.
Materials

Some of the materials needed for germinating milkweeds

1. Collect Materials

  • Asclepias spp. seeds, collected from or purchased for your specific ecoregion
  • Plastic bag with seal or zip closure
  • Stratification mix (one part perlite to one part vermiculite)
  • Bulb growing tray or other large shallow container with drainage holes
  • Seed germinating mix
  • Well-draining growing mix. Wildflower Center experts have successfully used several different growing mixes:
    • One part coarse sand to one part compost, or
    • One part coconut coir to one part coarse sand to one part compost, or
    • Composted pine bark (can add coarse sand)
  • Standard 4-inch pots

2. Soak and Stratify Seeds

  • Soak milkweed seeds in water for several hours or overnight; tap water is okay.
  • Once soaked, cool moist stratify the seeds for 14 to 30 days:
    • After the seeds have soaked overnight, put them in a sealed plastic bag filled with moist stratification mix. We recommend one part perlite to one part vermiculite (and by “moist” we mean like a damp sponge, no excess water).
    • Refrigerate the bag of moist seeds in their mix of perlite and vermiculite for two weeks. For some species of Asclepias, 30 days of cool moist stratification yields 85 percent germination or better.
    • Check your seeds every day or so; some seeds such as Asclepias incarnata and A. tuberosa may begin to germinate in the bag.
Milkweed seedings

Milkweed seedlings growing just after germination

3. Germinate

  • Transfer the moist seeds and stratification mix into a bulb tray of damp but not soggy germinating mix.
  • Cover lightly with germinating mix.
  • Mist to moisten soil surface thoroughly and check daily.
  • As seeds germinate, mist occasionally. If they are kept in a germinating mix that is too moist, the seedlings will “damp off,” which means they’ll die. Good air movement seems to reduce the potential for damping off, so if the weather is mild or warm, move the bulb tray outdoors under bright, indirect light.
Milkweed seedling

Milkweed seedling after being transplanted into a pot

4. Transplant

  • Once the seedlings have one or more sets of true leaves, gently transplant them into 4-inch pots or 5-inch liners filled with well-draining growing mix (see above).