Observations:
Week 1 – August Plantings vs. Cold Stratification
Our test is off to an exciting start! The Butterfly Milkweed is leading the pack with the highest germination rate so far, sprouting a full three days faster than the others. Showy Milkweed, on the other hand, is taking its time and has been the slowest to respond. For the seeds in cold stratification, we’ve tucked 30 of each variety into the fridge, where they’ll rest for another three weeks before being planted. Location: sunny South Florida.
Week 2 – Still Chilled Out
The cold stratification seeds are still snoozing in their little “winter” bags—cool, damp, and resting quietly. No rot and no surprise sprouts, which is a good sign. Just two more weeks before planting day! Outdoors, the Butterfly Milkweed was still the early sprinter last week, but this week the Pink Swamp Milkweed is stealing the show. Its seedlings look sturdier and could be ready for transplanting soon.
Week 3 – Growing Steady
The fridge seeds are in the home stretch, with just one more week until planting. Outside, the seedlings are moving up to bigger homes—most are now in 3” pots, and the Tropical Milkweed has graduated into pairs of 1-gallon pots. Among the natives, the Pink Swamp Milkweed continues to grow strong, while the Butterfly Milkweed still holds onto its “fastest starter” title. Showy and Common Milkweed, however, remain our slowest and least successful germinators. We’re keeping track of everything—days to transplant, germination rates, and which varieties truly benefit from cold stratification. We’d love to hear from you—have you tried this experiment in your garden? Please keep comments kind and encouraging—we’re all learning together!
Week 4 – Planting Day!
Winter is officially over for our cold stratification seeds! They’ve been warmed up and planted this week, and now the real comparison begins. We’ll continue to monitor their progress and see how they measure up against the outside germinated seedlings. Speaking of which, those outdoor starters are looking fantastic—now settled in 1-gallon pots and growing stronger by the day. Pictures coming soon!
Week 5 - Cold Stratification vs. Outside Germination – Week 1 Cold Stratification
We’ve officially reached week 5 of this experiment, but it’s only week 1 for the seeds that went through Cold Stratification. For this round, I started new trays of Butterfly Milkweed and Swamp Milkweed, giving them both a chance under the two germination methods—Cold Stratification and Outside Germination.
The early results are striking! Pink Swamp Milkweed clearly loves a cold nap before sprouting. After Cold Stratification, the success rate jumped to 93%, compared to just 2.5% for seeds planted outside without chilling. Butterfly Milkweed also showed a clear preference for Cold Stratification (70% success) but still performed fairly well outdoors (52.5%).
Common Milkweed and Showy Milkweed followed the same pattern. Common Milkweed had a 96.6% success rate with Cold Stratification versus 63% outdoors. Showy Milkweed wasn’t quite as dramatic, but still leaned toward Cold Stratification with 80% success compared to 75% outdoors.
Overall, it’s becoming clear that most of these milkweed varieties benefit from Cold Stratification—especially Pink Swamp Milkweed, which hardly sprouts at all without it. Butterfly and Showy Milkweed can still manage well with Outside Germination, but even they do just a little better after the cold treatment. I’ll be keeping an eye on how the sprouts grow and how the young plants settle into pots as the experiment continues.
