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do milk weed seeds need to be cold stratified

The plants are ready to be transplanted when they are about 3-6 inches in height. Before transplanting, acclimate the plants to outdoor conditions for a few days by placing them in a sheltered location during the day and then bringing them indoors at night. The seedlings should be planted 6-24 inches apart depending on the species (check the back of your seed packets for information). Newly transplanted plants should be watered frequently. Add mulch around the seedlings soon after planting. The mulch holds in the moisture and minimizes the growth of competing weeds. The seedlings should be fertilized 2-3 times during the growing season if using water-soluble fertilizer or once a season if you utilize a granulated time-release formulation.

Stratification
Seeds of most temperate plants need to be stratified, which is a fancy way of saying that they need cold treatment. 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 stratification period of 3-6 weeks, the seeds can be planted in warm (70˚F), moist soil. Without stratification, the percentage of seeds that germinate is usually low. Seeds from the tropical milkweed, Asclepias curassavica (and other tropical milkweed species) do not require this treatment. “Shocking” seeds that have been refrigerated by soaking them in warm water for 24 hours also seems to improve germination rates.

Milkweed seeds can be planted in prepared beds outdoors or started indoors in flats. We recommend the latter approach since germination rates are generally higher indoors and it is easier to establish your milkweeds with transplanted seedlings that are well-rooted and therefore more resistant to weather extremes and pests.

Introduction
Milkweeds can be propagated from seeds, cuttings, and, in some cases, from root divisions. This account will deal with storage, treatment and planting of milkweeds seeds and will briefly touch on propagation from cuttings.

When to Plant
Milkweed seeds can be sown outdoors after the danger of frost has passed. Refer to the seed packets for special instructions on sowing the seeds. Keep in mind that seeds have a range of soil temperatures at which they will germinate. Also, remember that under sunny conditions the soil temperatures can be much higher in the daytime than the ambient air temperatures you experience. Plant the seeds early since those planted late in the season may not germinate because of high temperatures. In addition, new seedlings from late plantings can "dry off" before they are even noticed. Asclepias incarnata (swamp milkweed) and A. syriaca (common milkweed) germinate poorly at high temperatures (>85˚F). However, other species such as A. curassavica (tropical milkweed) and Cynanchum laeve (blue vine) germinate well at these temperatures. Germination outdoors depends on soil moisture and temperature and could take several weeks if conditions are not ideal.

Ok, so you may have read or heard that some seeds need to go through a winter in order to germinate. The process of going through a winter actually has a name, it is called Cold Moist Stratification. And, that is how mother nature does it!

So, if you would like to read a very successful milkweed seed germination guide with pictures, then read on……

*We wrote a guide for harvesting Milkweed Seeds without making a mess. You may want to have a look, it is quick, clean, and easy.

Results

Note – Milkweed Seeds should be winter-sown or cold stratified for at least 30 days to achieve a high germination rate.

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So, below are some pictures of my results from 2020’s crop of Milkweed grown from seed! I’ve been growing various Milkweeds from seed since 2013, and have germinated hundreds of seeds. This method is by far the simplest, and is very effective at producing seedlings.

I have successfully used my process on the species of Milkweed listed below: