Milkweed seeds and propagationBy Cathy Downs on June 19, 2014
Earlier I wrote about collecting milkweed seeds. I have received many requests for a follow up article on cleaning, storing and propagating the milkweed seeds.
Cleaning milkweed seed from the pod can be a time consuming and messy business if left for too long. It is not a task to be undertaken inside the home as the chaff tends to fly about with a mind of its own. There are a variety of ways to separate the seed from the chaff, or fluff. If you were able to pick the pods before they split wide open the following method is easiest. Open the pod at the seam and grasp the silk together firmly by the tip. Gently lift the seed and silk from the pod with one hand. Then you can literally “tickle” the seeds into the palm of the hand or a container by sliding your fingers along the silk from top to bottom with your other hand. Keep a firm grasp at the top and continue sliding the hand down as seeds come away.
A fellow Monarch Conservation Specialist, Candy Sarikonda, put out this YouTube video describing this method in detail. Our milkweed pods tend to be dark in color but the pod she is using is from the Common Milkweed (Asclepias syriaca) and looks green to us. Although the pods look different the method will be the same.
If you were not able to get to the pods before they burst open you can empty the seed and chaff from the pods into a brown grocery bag and shake the contents repeatedly. The ripe seed will fall to the bottom and you can release the fluff through the top of the bag. Just tear a slight hole in the bottom corner of the bag to release the seed into a tray or container. I find this method less time consuming and more effective than any other methods. I do the releasing out in my meadow in case there are still a few seeds attached.
Other methods I have heard of include burning the seeds to remove fluff. After a test for germinating success by the author, however, it was decided that the burning method destroys seed germination (and it’s a little dangerous…fluff is very flammable) some folks put it through a vacuum cleaner; some have fancy equipment that churns the seed. You can find several of these methods and engineering diagrams on the internet. Personally, I like to keep it simple.
If you don’t have the time to glean the seed right away milkweed pods should be dried thoroughly for at least an hour in a paper lined flat tray to discourage mold. The pods once dry can be stored in brown paper grocery bags until cleaning time. You can use the same bag to separate seed as above. Just be warned when you open the bag to begin cleaning fluff will be all the way to the top. Clean seed should be kept stored in paper in a cool dry place. I use lunch size brown bags, fold the top over, staple shut and write the specie common and botanical name, date and county location of origin.
There are many methods, videos and essays on propagating milkweeds. The one common thread seems to be the vernalization or cold stratification of the seed. Monarch Watch details vernalization and scarification as follows:
Seeds of most temperate plants need to be vernalized, which is a fancy way of saying that they need cold treatment. The best way to give the required vernalization is through stratification. To stratify seeds place them in cold, moist potting soil (sterilized soil is best but is not required) in a dark place for several weeks or months. Since most people prefer not to place potting soil in their refrigerators, an alternative is to place the seeds between moist paper towels in a plastic bag. This procedure works well, in part because there are fewer fungi and bacteria available to attack the seeds. After a vernalization period of 3-6 weeks, the seeds can be planted in warm (70?F), moist soil. Without vernalization/stratification, the percentage of seeds that germinate is usually low. “Shocking” seeds that have been refrigerated by soaking them in warm water for 24 hours also seems to improve germination rates.
Even after vernalization/stratification, seeds of many plant species will not germinate. In these cases, the seed coats appear to require action by physical or chemical agents to break down or abrade the seed coat. “Scarification” with some type of physical abrasion that breaks the seed coat usually works and can be accomplished by placing the seeds in a container with coarse sand and shaking the container for 30 seconds or so. Scarification may be required for some milkweeds and might improve the germination rates of other species.
I use a warming pad when I start my milkweeds from seed. I use 4” peat pots in starter trays as it gives the plant more opportunity to put out the all important tap root. Germination usually takes place within a week to 10 days. Once the plant shows two sets of real leaves I put the entire peat pot into a one gallon container with a mix of 2/3 garden soil, 1/3 potting soil and about 1/10th granite sand for drainage. This way the transplant experiences the least amount of shock. Milkweeds are notoriously tricky transplants and I find the older the rootstock the more success the plant will have. I will not put a milkweed into the ground before the rootstock is at least 10 months old or more. If you have room to winter over the gallons even better! I water only when the pot is dry to about 4 inches.
Bobby Gendron has a great two part video that explains in detail planting methods for milkweed using a seed starting kit.
I find that Mother Nature always knows best though. Every year at the beginning of November during a light rain or drizzle I walk through my property scattering any seed I have left to the four winds. My milkweed plant count has tripled in the six years I’ve been doing this. Or, perhaps, I’m just paying more attention.
I continue to offer my services as a distributor of surplus milkweed seed. If you decide to ship seed to me please pack in paper or cardboard marked with your name, county of origin and the species common and botanical name. I will find a home for your seed among the many requests I get.