Growing Method for Seeds
Species: Asclepias viridis, A. asperula, A. incarnata, A. verticillata, A. oenotheroides, A. tuberosa
Author: Barbara Keller-Willy BarbaraAnKeller@aol.com, Monarch Gateway
Feel free to share but give credit if emailed or published.
Milkweed Sprout Harvesting Propagation Method (71-78% success depending upon type of milkweed)
- Pour 4 cups vermiculite in zip lock bag.
- Put seeds into dry vermiculite and mix, shake to distribute seed.
- Make vermiculite slightly moist twice a few hours apart to achieve moist not soggy. (1-2 cups water total). Goal is for all vermiculite to be moist, not dry, not soggy.
- Put in refrigerator for 3 weeks. I use 36 degrees exactly with seed placed to rear of refrigerator to minimize temperature changes.
- Remove from refrigerator and place bag in sunny window or under fluorescent light source until you begin to see evidence of first sprouting (white sprouts).
- Using13 x 9 foil pan or plastic tray, slide entire mix into pan trying to keep same top orientation. Gently spread out into pan.
- Lightly water with lukewarm water (replicate warm summer rain) I use spray faucet.
- Cover tray/pan tightly with plastic wrap. Sit in warm, light location.
- When the first white sprouts begin appearing, you can plant any seed that shows evidence of sprouting or leave in tray until it gets first two leaves. Save unsprouted seeds, cover with plastic. Pic below is second Asclepias veridis harvest. A third harvest may occur if unsprouted seeds are placed outside once temperatures allow.
- Prepare seed starter medium. Starting with an over the counter seed starter mix, add a fine top soil to replicate your native soil, add perlite, add vermiculite to potting starter mix. (4 part seed starter, 2 part local top soil, 1 part perlite, 1 part vermiculite) (I also try to borrow some soil from end location and mix with potting starter mix.)
- Fill plug tray or 2" pots with starter medium. Water gently to avoid washing out mix. Soak soil through to bottom of pot. Sit aside to drip.
- Using fingers or pencil/chop stick, poke hole in each moist prepared plug/pot gently lift sprouting seed from sprout harvesting tray, place in prepared hole, leaf/seed side up. Press soil to surround root.
- When planting sprouted seedlings the biggest danger is not planting deep enough. Watch your seedling and add soil if root becomes exposed.
- Using an oscillating fan to simulate normal wind for the planting area will slightly slow height growth but strengthen the stem system. Watering with rainwater increases viability from about 78% to almost 85% or higher.
- Do NOT frequently repot milkweed. Plant directly into 1 qt pot where plant should remain for 1st two years.
- Soil should remain consistently moist for the first year or two for best results. Remember, a seedling only has a tiny tap root compared to what it will have eventually.
- Several different things (heat, lack of rain/water may cause your plant to appear it has died. It HAS NOT!!!!!! Keep watering. Sometimes it takes months for the dormant plant to return. KEEP WATERING! DO NOT STOP!!!!
Method Used by Laura Penn
Based on my own experience here is what has worked for me.
1) Gather milkweed seeds locally.
2) Scarify and cold stratify seed after collecting it in the fall by doing the following.
a) Clean seed from coma / fluff / chaff.
b) Put about 25 seeds in one sandwich sized ziploc bag with about 1-2 cups of dry coarse sand.
c) Close ziploc bag, and shake with sand and seeds inside to scarify seed coats. Shake for ~ 5 minutes.
d) After shaking, open bag and add just enough water that sand is damp but NOT wet. Only add a 1/4 teaspoon or so at a time and shake to mix it in and continue until all sand is damp.
e) Close up the bag again and put in the refrigerator at least 4 weeks. Could be as long as 6-8 weeks to cold stratify. (mimics the winter season)
3) Pulsing: After the refrigeration period, sometime in early spring, begin removing the sandwich bag from the refrigerator during the day, leaving it on your kitchen counter in a bright but shaded condition, and then returning the bag to the refrigerator at night (pulsing) to mimic the spring season. Continue this for about a week or two. Be sure to start looking carefully at the bag when you remove it and put it back in the refrigerator as you will start to see seeds germinating. When you see seeds germinating, VERY gently remove only those seedlings and let the rest continue in the damp sand.
4) Putting seedlings in pots:
a) I use cardboard (degradable) pots for the germinated seedlings. (You can buy a dozen for $1 at the dollar store.) I mix up a light sandy base potting soil mixture with just a very small amount of native soil where the seeds originated from (if possible). In cardboard pots, put a small bit of soil in the bottom and then holding the seedling gently by the starter leaves, very gently spoon soil around the tap root to fill the pot. Take special care not to break the root. I like to sprinkle a little ground cinnamon around (but NOT on) the seedling, as reportedly this is a natural anti fungal agent and it seems to reduce damping off in my experience. Cornmeal is supposed to also be a natural anti fungal if you have that on hand.
b) Place cardboard pots in a shallow tray of water and let sit for about 30 mins until the cardboard is completely wet to top of pot from wicking up moisture, then remove from water tray.
c) Put all cardboard pots in a clear plastic container that is about 4-5" deep and cover with saran warp. Poke a few holes in top of saran wrap with a fork. Put the plastic tray in an east or south facing window (or greenhouse) with dappled shade.
d) Watch seedlings daily and be sure to keep evenly moist, but not too wet. This is critical in the early stages.
e) After a week or two and certainly by the time seedlings grow their first set of true leaves, gradually begin to expose them to more open air by removing saran wrap for longer periods of time each day and then later giving them a little exposure to outdoor environment on mild non windy days. Continue to keep seedlings moist with bottom watering via water tray.
5) When seedlings are a few weeks old, bump them up into larger pots even if their top growth is still small since the plant is focusing its growth on the tap root you cannot see. Here is where the benefit of the cardboard pots comes in: just plant the whole cardboard pot into at least a gallon size container with loose potting soil and again adding a small amount of native soil to the mix. Milkweeds reportedly do not like to have their roots disturbed so the cardboard pots allows them to get into a bigger pot without that irritation.
6) Continue to provide regular moisture with bottom watering as plants grow & slowly transition pots to be completely outdoors in morning sun & afternoon dappled shade.
7) Some growers say keep plants in pots at least a year before out planting, but if you can and will regularly water the young plants in your landscape, I have had success out planting them after 6 months.
Note, these plants will NOT bloom the first year they are in the ground as they are still busy growing that root system, so be patient and don't get discouraged. Year 2 of plants being in the ground they should bloom (assuming they are not eaten by caterpillars) and each year after, even though the plant dies to the ground each winter, the plants come back fuller and larger than the year before with more blooms. DO NOT transplant from place to place in the landscape as they do not like to have their roots disturbed.
Good luck and stick with it! It's so rewarding to see all the different butterflies and insects that use native milkweeds as nectar and host plants!