Winter sowing enthusiasts usually will say you can begin around the winter solstice. They will start with seeds for the hardiest plants at that time. Wait until late winter to winter sow tender bedding flowers and vegetables. In Nana’s zone 7a garden, we anticipate the following schedule for our WS tomato seedlings:
First week in March–sow seeds in containers and put them outside.
First week in April–seedlings have germinated.
Last week in April–transplant seedlings into individual pots.
Second week in May–seedlings are ready for putting into the garden or selling at market.
FOR ALL WS SEED STARTING CONTAINERS
It is not necessary to use seed starting mix for winter sowing. Regular potting mix is fine. Make sure it is already moist before you put it into the container. Once the seeds are sown it is a good idea to put the container in a pan of very warm water so that the media can become thoroughly moist before you put the container outside.
All winter sown containers need several holes in the bottom for drainage. It is simple to poke a hole in a Styrofoam container with a pen. Much of Winter Sowing is done in recycled plastic containers, and a handheld drill can easily create these holes. Starting with tiny holes and progressively widening them with larger drill bits will help to prevent cracking of the plastic. Holes can also be enlarged somewhat by “twirling” the drill bit or nail once it is in the hole.
Once the drainage holes are created, here is how to prepare the various types of containers for the great outdoors:
HOW TO PREPARE DIFFERENT TYPES OF WS CONTAINERS
Many types of containers can be used. They should have a vented, clear lid, drainage holes in the bottom, and a large opening for easy access to the seedlings. Here are instructions for some containers that have been successful for us:
Gallon Milk Jugs
A look at online Winter Sowing forums shows that the most commonly used container seems to be the plastic gallon milk jug. To prepare the milk jug, wash the inside thoroughly (possibly by putting a drop of dish detergent inside, filling it halfway with water, capping it and shaking it vigorously) and rinsing it out. When it’s dry, cut it according to the directions below using scissors or a sharp knife. (I actually start the cut by puncturing it with a knife, then use scissors to cut it the rest of the way.) Here’s where to make the cut:
Starting at a level just below the handle and to one side, make a horizontal cut all the way around the jug EXCEPT for the space directly below the handle itself. Leave that part uncut so that it creates a “hinge.” See the picture below.
Make several holes in the bottom of the jug. For stabilization, and to make sure you don’t accidentally slip and damage the counter, put the inverted jug over the open mouth of another container:
Flip the jug over so that it is right side up, and put in about 4″ of moist potting mix. Sow the seeds according to the package instructions. Label the container with a paint pen (permanent markers fade).
Alternatively you can insert a variety label into the potting mix. (See picture below.)
Punch two holes on the front corner (directly opposite the handle), one on the top section and one on the bottom section, near the cut edges. Insert a twist tie and use it to tie the jug closed.
Now wrap packing tape around the entire cut edge to seal it. Throw away the cap (you don’t need it) and put the jug outside–no matter how cold the temps are!
Margarine, Cheese and Coffee Tubs
First, make drainage holes as stated above.
With the lid snapped onto the tub, use a knife to make a slash near the outside edge of the lid.
Take the lid off, insert scissors into the slash and cut around the edge, keeping the rim intact.
Put at least a 4” layer of moist potting mix in the bottom of the tub and plant seeds according to package directions.
Cut a piece of plastic wrap and drape it over the open tub.
Snap the rim on the tub, capturing the plastic wrap in between and trying to keep it stretched as tightly as possible.
Use a knife to make a few slashes in the plastic wrap for air circulation.
Seeds sown and ready to go outside.
Denny’s To-Go Containers
Use a pen to poke holes in the bottom of both bottom sections (the container is divided into two sections, with a “wall” in between).
Put a thick layer of moist potting mix into both sections and sow seeds according to package directions.
Label the seed variety by either (1) inserting labeled sticks in the potting mix, or (2) writing the variety on the outside of the black container with silver, gold or white paint pen.
Snap the clear, domed lid onto the container. (The lid already has holes for circulation.) Put a single piece of tape on one or both sides where lid meets bottom, thereby taping the lid down in one or two spots.
Pass a piece of ribbon or twine underneath the container and tie it in a bow on top. (A bow is easily untied and retied, as opposed to a double knot.) Hold the ribbon/twine in place in at least one spot with tape. Another piece of tape might be placed lightly over the bow to keep it from coming undone.
The Baggie Method
Label the zip lock baggie with the variety name using paint pen. Snip a tiny piece off of each of the two bottom corners. Fold the baggie in half along the center vertical line, with left edge meeting right edge, and snip a tiny piece off of the resulting bottom corner.
Unfold it and now you should have little drainage holes in the two bottom corners and the bottom center.
Open the baggie and put about a 3-4” layer of potting mix in the bottom, pressing it down so that the baggie will stand on its own. Sow seeds according to package directions.
Place a spring-operated clothespin or small office binder clip at one end of the zip lock mechanism, perpendicular to the baggie, propping that end open.
Run your fingers along the top of the baggie, closing the rest of the zip lock edge.
PUT THEM OUTSIDE RIGHT AWAY!
If you leave them inside, even for a day or two, the warmth of your house might cause premature germination.
It won’t hurt them if it is cold, or snows, before they have germinated. Don’t coddle them by bringing them in if the temperatures drop. They will germinate in the spring, once the weather warms. The little covered containers act as miniature greenhouses, so the temps inside are warmer than the ambient temperatures are. The seeds will germinate earlier than they would if you just put them directly in the ground.
If there is a predicted freeze once they have germinated, you might want to throw a blanket on them overnight.