Seed Collection & Prep
What's up with this extra step needed for your milkweed seeds in the spring?
If you've been given some milkweed seeds or collected your own in the fall, they missed a step normally done by Mother Nature. Left to nature, they get exposed to our cold, wet winter weather which helps break down their extra tough shells.
We can mimic Mother Nature with one of the two methods shown below (not both). For a small number of seeds, use the 7-day method below and immediately pot them. If you have a larger amount, try the method on the right and start indoors or sow outdoors.
When to pick?
It is critical you leave the pods on the plant until the seeds have turned brown. Seeds will not continue to ripen after you pull the pod from the plant.
Some people like to put an elastic band around the seed pod to prevent it from opening and "exploding" once ripe. Left to Mother Nature, the seam will split on the pod when ready, and the air will dry out the silk attached to each seed. The wind then disperses the seeds. Showy milkweed seed pods hold about 250 seeds, as compared to Swamp or Butterflyweed pods which have roughly 25-50 seeds.
7-day germination method
Use fingernail clippers to clip off the pointy tip of each seed. Place the seeds in an inch or more of water in a bowl that can be placed on a warming mat for the week. A small clear glass bowl covered with plastic wrap works well. You will start to see germination by day three.
When the majority of your seeds have germinated, put them in pots to start indoors or outside if they won't freeze.
Photo below courtesy Bradd Grimm
Cold Moist Stratification
30-day method - for lots of seeds
Use a spray bottle filled with water to dampen a paper towel. Sprinkle half of the paper towel with a single layer of seeds. Fold the other damp half over, making a paper towel sandwich.
Seal the damp paper towel/seeds in a ziploc baggie in the FRIDGE (not freezer) and leave for 30 days.
Time this process according to whether you will start the seeds indoors late March or sow the seeds outside after last risk of frost (first week of May).
Showy milkweed roots
Asclepias speciosa spreads via a horizontal rhizome. Thanks to Tommie Nielsen for this amazing photo that shows it so well. If you want to remove some showy millkweed once it has grown too far, you must dig down to the horizontal level and get this main line out.
Growing in Pots
Utah's native milkweeds can be grown in pots, although it's not ideal. Most of our native milkweeds are drought tolerant once established due to the long tap root that will go down 10 feet or more and horizontal spreading. If you plant milkweed in pots, it will not be drought tolerant, so you will want to water it as often as needed to keep it healthy.
Swamp milkweed (Asclepias incarnata) and butterflyweed (A. tuberosa) do not have the same type root system, and are less likely to spread.
Swamp milkweed can be used successfully in our northern Utah plantings if there are plenty of other pollinator species around it to shade the base and help retain moisture. It will still require more water than the others, but it's not like it has to be planted in a "swamp" or wetland area - although that's where it thrives.