Starting Native Seeds
Many seeds native to colder climates require cold stratification in order to germinate. Cold stratification simply means exposing your seeds to cold and moist conditions that they would receive in their natural environment. If our native seeds only required a warm rain to sprout, many seeds would germinate in the fall only to be killed off by a harsh winter. Instead, repeated bouts of rain, snow, and ice are required to break down physical and chemical inhibitors, resulting in seeds that germinate once the risk of intense freezes are over
Luckily, cold stratifying your seeds is as simple as sowing them on top of some soil in the fall or winter and leaving them be until spring. We have found that the most successful method is to sow seeds densely onto a small pot (4-6” wide) filled with weed-free compost or potting soil. We label our pots with a grease pencil, so the text is clear come spring. Next we sprinkle some sand on top to weigh the seeds down without blocking too much sunlight. Finally we put the seeds on the north side of a building or a tree on a FLAT well draining surface. Keeping the seeds flat over winter ensures that they won't pool in one corner after a heavy storm. Once the risk of extreme winter temperatures has passed, we bring the pots to a sunnier south-side location and wait for germination. This usually occurs in May, but some species will take more or less time.
Another method to stratify your seeds is to place them in a moist medium inside the fridge. Some strategies we have tried include folding the seeds inside a damp paper towel or mixing them in slightly moist soil, sand, or vermiculite. Then you simply put the seeds inside a labeled plastic bag and wait 2-3 months for germination. This method does have an increased risk of mold forming on the seeds. If this occurs, you can try rubbing the mold away, or wash the seeds, although this may not work with many small seeded plant species.
Seeds are an incredible evolutionary adaptation and every time one germinates we feel humbled to be part of the process. Give it a try and let us know how it goes!
