Christmas is gone but winter stretches on. The outdoor garden lays dormant, soil frozen and covered with snow. In my greenhouses, the veggies are taking a short rest, waiting for a burst of growth as soon as days lengthen. Maybe they are trying to teach me patience, remind me to stay in hibernation. Not likely!
With the new year upon us, it’s time to get out those seeds and start planting. Yep, you heard me right, its time to sow seeds. If you think about it for a moment, it makes perfect sense.
In nature, a seed drops from the plant in autumn and is covered by falling leaves and decaying organic matter. It sleeps throughout the winter season. As the soil warms and the days lengthen, the seed knows when to sprout. It does this slowly, carefully, reaching its roots deep into the earth before it raises its vulnerable leaves into the cool air. Each seed has millions of years of inherent knowledge about how to survive. If it ignores that knowledge or miss-times its emergence, it dies. In this way, only the strongest and fittest plants survive. Those that make it are the best!
We have been led to believe that seeds need pampering: sow them at the perfect time in artificial growing medium, set them in heated plastic trays under florescent lighting. Only them will they consent to germinate. This may be true of some fragile hybrids but not for most plant varieties. In fact, many plant seeds need a period of intense cold before they will sprout. This is called stratification. Many annuals and perennials as well as the majority of trees and shrubs need their seeds to cold stratify.
For example, chilling is essential if you want to sow salad greens in July or August. In the height of summer, I pop seed packets of lettuce, onions and particularly spinach into the freezer for a week or so before I put them in the ground. Without this stratification, I get as little as 10% germination of summer spinach. With a little cooling off time, I can expect near to normal numbers of seedlings in August.
Dedicated and impatient gardeners have run with these ideas. Gardening forums are filled with postings about winter sowing. Practically every variety of flower, herb and vegetable can be cold sown. It is particularly useful for those perennial and annual flowers that you buy in the garden center around Mother’s Day. With a little effort and less expense, you can have as many bedding plants as you ever wanted. It even works for tomatoes and cucumbers.
Winter sowing has many benefits. The seeds germinate naturally and establish strong root systems. Temperature fluctuations stress both seeds and seedlings so only the strongest and most healthy plants survive. Cold sowing is undemanding: you plant whenever you have time in whatever container you can lay your hand on. Best of all, it gives you something to do in those empty winter months.
How to do it
Cold sowing is simple. You plant seeds in a container with a transparent cover and leave it outdoors. As the weather warms up, the seeds germinate and your seedlings are ready to transplant into bigger pots or straight into the garden. That’s it! Well… not quite. Like any growing technique, there are a few things you need to know to ensure success.
First find your containers. The essential elements are depth and a transparent or translucent top. You need a minimum of 3” of soil in the pot for strong root growth and adequate light for the leaves to stay green and strong.
Gallon jugs for milk or water are very popular. Cut them almost in half near the handle, leaving a ‘hinge’ of plastic. After sowing, the parts can be taped shut with masking or duct tape or connected with a twist tie. Pop bottles can also be cut in half, with three wedge-shaped slits in the top half so it slips over the bottom. I have lots of gallon plant pots, so I simply put a thick plastic bag over the top, held in place with a large rubber band.
Drainage and Air
Whatever container you use, make sure there are drainage and air holes. Stick a knife three times through the bottom of any solid container. Plant pots already have large holes. I place pebbles over these to restrict water loss. Transparent covers need to let in a certain amount of air without allowing the soil to dry out. Unscrew the cap on jugs or bottles; pierce a few holes in plastic bags.
Soil and Seeds
The seedlings grow in the pot until they are somewhat mature with true leaves, so soilless mixes may not provide enough nutrition and mass for the roots. I make my own traditional seed mix: 1 part sand, 2 parts compost, 4 parts peat moss or coconut coir — all sifted through a ¼” mesh. You can also use garden soil mixed with a little coconut coir if your soil is rich and fertile.
The soil should be at least 3” deep and well moistened. Place the container in a bucket of water so it gets watered from the bottom. Seeds are planted in the normal way at a depth of about 2 times the smallest dimension of the seed. Sow any variety you think might grow and be sure to label every container. Plant moderately thickly – expect a survival rate of 80% or less.
Location and Care
The main threat to your plants will not be cold but overheating and drying out. Do not put the containers in full sun; the North side of a shed works well. It is fine if they get covered with snow but they do not want to sit in a puddle of water. If you have harsh winters, surround the containers with mulch such as leaves or straw or dig them a little into the ground. This helps modulate fluctuations in temperature.
Make sure the soil stays somewhat moist; check every week or so and add water as needed. When the seedlings are up, protect from frost with row covers and blankets and start feeding with compost tea and dilute nutrients. If you have the option, move the seedlings into your greenhouse in March to enjoy early flowers and vegetables.
Now is the time to throw off your gardening doldrums. Pull out all those seed packets, rummage through the recycle bin and take a chance. With a little ingenuity, you will be flooded with so many spring plants you can supply all your friends. What have you got to lose?