Even though you can’t plant your entire garden now, there are certain seeds that can be started outdoors right now in Maine.
The technique that allows this — referred to as winter sowing — involves planting seeds outside during the winter, often in some sort of container. The container spends all winter outside, exposed to the cold, which is actually good for certain seeds. When temperatures warm up in the spring, the container provides the perfect microenvironment for the seed to germinate before transferring it to its permanent location in your garden or field.
How does the process work, and which seeds work best for winter sowing? Here’s what you need to know.
Why sow in the winter?
While it may seem counterintuitive to plant anything during the colder months, it’s really what nature intended for certain plants.
Left to their own devices, certain plants release seeds in the summer that fall to the ground. Over the fall and winter months, those seeds get covered with leaves and other materials as they slowly sink beneath the soil in a dormant condition.
“It’s really doing what nature does,” said John Bliss of Broadturn Farm in Scarborough. “The less ‘domesticated’ a crop is, the more successful winter sowing can be.”
Flowers tend to be less domesticated than vegetable crops, according to Bliss.
A plant is considered domesticated when its life cycle and appearance has been significantly altered over multiple generations by humans. To be successful, these plants need human attention to grow and produce.
There are many wild flowers, perennials, shrubs, trees and vegetables that have to go through a period of cold before they can germinate. For some domesticated crops, exposure to cold temperatures causes them to germinate faster in the spring.
Winter sowing duplicates that natural process.
Which seeds are good to sow in the winter?
Edible options for winter sowing in Maine are some of the cool-season crops such as broccoli, cauliflower and cabbage. Leafy greens including lettuce, kale and bok choy are hardy plants and do well with winter sowing. You can also sow herbs such as sage, oregano, dill and mint during the winter.
For other ideas on what to plant, check your seed catalog or seed packets. There should be notes on germination requirements. Key things to look for are anything that can reseed, colonize, self-sow, is hardy, withstands frost or requires pre-chilling or stratification.
“These are plants that have had to figure out how to grow with self-seeding in cold areas,” Bliss said. “But there are things we can do to help them out.”
How do I winter sow?
Instead of planting your seeds directly into the frozen or snow-covered ground, you need a container of some sort. This not only makes it easier to plant the seeds, it gives them the same sort of protection they would have gotten naturally had they landed on the ground last summer.
Items like empty plastic gallon milk jugs, large soda bottles or large clam shell-type containers similar to those that hold grocery store rotisserie chickens work well. The main thing is to use something that is clear or at least opaque enough to let in some sunlight.
Whatever you are using, if it doesn’t have a screw-top or cap, you need to poke holes in the top to provide good air circulation for the seeds and in the bottom so water does not collect, stagnate and turn your germination container into a mini-swamp.
If you are using a milk jug or soda bottle, slice it almost completely around, but leave an inch or so to act like a hinge.
Add about 4 inches of potting soil to your container and sprinkle your seeds on top of the soil. Gently press them into the dirt and sprinkle a thin layer of soil over them. Close the container and seal it shut with tape. Mark each container with what you have planted in it.
Now all that is left to do is place it outside and forget about it until spring. Pick a location that gets the best winter sun and as out of the wind as possible. Moisture will naturally form inside the container to keep the seeds moist. When the weather warms up they will germinate and sprout.
What next?
When you notice the seeds are sprouting and growing, check on them periodically. As temperatures warm, you may need to poke larger holes in the container so the seedlings do not get too hot too fast.
Once the seedlings reach the top of the container, they are ready to transplant into your garden or field.
