Did you know that most Milkweed seeds and many other perennial plants need a period of cold stratification in order to germinate?
In using the Outdoor Methods, it is best to plant your seeds after the first frost. I live in Nebraska where the first average frost happens around October 5th. (click here to find out when your average first frost is). I am planting Common Milkweed (Ascepias syriaca) because it is the most common species of Milkweed growing in my area and I know it needs a cold stratification period.
The "Fall Planting Method"
Fall planting is a traditional method of cold stratification. The best time to plant Milkweed seeds in the Fall when the first frosts start to occur. I recommend planting them directly in the ground, however you can plant them in pots with some additional attention.
1. Choose an area where you want to grow your Milkweed plants. Make sure it has proper sunlight and is in a slightly protected area.
If planting in pots, make sure they are protected (i.e. against the side of a building or next to straw bales). Make sure the pots are not in the drip-line of the building so that they could potentially fill with water and then freeze. However, snow-melt is an important part of the process so do allow snow to cover the pot.
2. Sprinkle the seeds on the soil and mulch with a couple inches of straw or leaves.
Note: Do not pack the mulch down as it is important to have a bit of air flow to deter mold and fungus from growing.
3. Sprinkle water over the seed bed if soil is dry.
4. Mark the area so you don't forget where you planted.
5. Be patient. They will not germinate and start sprouting until Spring and sprouting will not occur all at the same time as with most cultivated varieties of plants. These are wild plants that will have more genetic variation and will be more likely to survive once they have become established.
The "Winter Planting Method"
This method is also called "Snow Planting". It is an easy, fun method that should spark the interest of children and adults alike!
During the winter after a heavy snow, broadcast your seeds out on the snow. Believe it or not, many of them will come up in the spring! The moisture will soften their seed coats and essentially wake them up.
Make sure it is in an area that you want the plants to grow and will have plenty of sunlight in the Spring and Summer.
Have fun experimenting with different methods of cold stratification. You can even plant a small batch of Milkweed seeds in the Fall, Winter and Spring! Why not? Each time you will learn something new and know what works best for your area next time. Don't give up and record your findings!
I have just covered how to sow Milkweed in the Fall and Winter in this blog. If you want to opt for the Spring planting stay tuned for Part 2 of the Cold Stratification 101. In the meantime, keep you Milkweed seeds in a dry, aerated envelope and store in a dark place for the Winter. If I plant in the Spring, I generally start the Cold/Moist treatment for Milkweeds 30-60 days before the last average frost in my area.