WINTER SOWING

 WHAT IS WINTER SOWING?

Winter sowing is planting seeds outdoors in a protected container during winter. The container remains outdoors until the seedlings emerge in the spring.

There are benefits to winter sowing. When you direct sow in the ground, the seeds are at the mercy of Mother Nature. They can be washed out in downpours; eaten by animals; desiccate in the wind; or rot in the soil. They are more protected in a container and the spring seedlings do not need to be hardened off before planting in the garden. Winter sowing is ideal for those with limited indoor space for seed starting. No special lighting or equipment is required for germination.

The best time to winter sow perennials and annuals is generally December to March depending on the weather conditions in your area. These seeds receive a consistent period of moist, cold temperatures before germination occurs in spring.

You can provide a protected, cold environment in a DIY mini greenhouse for seedlings. This can be a family-friendly activity for parents and children.

INSTRUCTIONS

Clean container — Wash and rinse with mild water/bleach solution (1 Tbsp. per gallon) milk jugs or suitable (material that lets light in) containers. Discard the top. The opening allows rain and melting snow to keep the soil moist.

Cut container — If not using a container with a hinged lid, measure 5” up from the bottom and mark around the sides. Lay it on its side and cut all the way around, leaving about 2” (under the handle, if using a jug with a handle) so that the top hinges open. Children can measure and mark.

Create drainage - Cut 1/8″-1/4″ diameter holes by using a knife, screwdriver or nail to poke 6 to 8 holes and 4 to 6 holes about ½” up from the bottom on the sides. This is important--if you don’t make drainage holes, your seeds will drown! If using a container with a hinged lid, poke a few holes in the top of the lid, too, to let rain and snow in.

Add soil —Use a potting soil mix that's light and drains well. Do not use garden soil or compost and avoid mixes that feature water retention or moisture control properties. Put the soil in a tub and pre-moisten it. Soil should be moist like a damp sponge, light and fluffy and drain well. Fill the container with 2 to 4" of a potting soil mix¹ that's light and drains well.

Sow the seeds — Space them a bit closer than on the packet but at the listed depth. Be sure they are covered. Seedlings can be thinned after germinating in the spring.

Seal the container – Close the hinge, seal the cut edges with duct tape, and leave the top open.

Label the container - Label with the type of seed and date of sowing with a permanent marker.

Set outdoors and leave! – Site the container in an area that receives winter sun. Do not place the container on a covered porch as the seeds require the moisture from the rain and snow. They should experience all the weather conditions they would in nature. Place containers in a milk crate if conditions are windy. Forget about your containers until the spring when the seed germinate.

¹ If you are using toilet roll or paper seed pots, put an inch of soil in the bottom. Fill the pots with soil and set them in container, fitting them in tightly and firmly down on the soil. Fill the soil up to the tops of the tubes. (See eBlog on paper seed pots  )

Spring Care

In spring, once the weather starts to warm up,  check on the moisture inside your mini greenhouses. Check for condensation or lift the containers for weightiness. If some of your containers have condensation but others don't, it is a good bet that those that don't have condensation could use a good drink of water. Also, if some of your containers are lighter in weight when compared to other containers it is a good bet those lighter containers could use a drink, too.

The easiest way to water your containers is to soak them. Put a couple of inches of water in a bucket or large plant saucer and set the container into the bucket of water for approximately 15 to 30 minutes until the container has absorbed as much water as it is going to. Don't worry about over watering, the excess will drain out the bottom holes.

On warm spring days, open the container to keep the seedlings from getting too warm. Close again (no need to re-tape) if evenings are cool. When seedlings are tall enough, or reach the top of the container, and have grown their first few sets of leaves, it’s time to plant them into the garden. They should have a good root system but remove carefully as roots may be tangled together. Some plants will need to wait until after the last frost date (May 12 for Franklin County). Cool weather crops, such as lettuce, can be planted out 4-6 weeks before then.

When seedlings are ready to transplant, be sure to bury the tube in the ground so the edge is below the soil surface. 

Spring Watch for winter sowing

Other resource: Penn State Winter Sowing

CKagan, Master Gardener

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