An Adventure in Winter Sowing

Written By Potted Blossom

How to Winter Sow: A Gardener’s Guide for Zone 7

When the days are short and the garden is resting, I start itching to get my hands back in the soil. Here in Zone 7, we’re lucky to have around 150 planting days — much longer than St. Anthony where I started my business, but still not quite enough for an impatient gardener!

If you’re like me and can’t wait for the season to start, winter sowing is the perfect way to get an early jump without needing grow lights, heat mats, or a greenhouse.

What Is Winter Sowing?

Winter sowing is a simple method of starting seeds outdoors during the cold months, using mini greenhouses made from clear plastic containers, such as milk jugs. Seeds are sown in potting mix, sealed inside the jugs, and set outside to weather the season. As temperatures naturally shift, the seeds go through the natural process of freeze and thaw which results in cold stratification. As the days warm up they then sprout at just the right time.

The result? Hardy seedlings that are already acclimated to outdoor conditions — no hardening-off required!

Why Try Winter Sowing in Zone 7?

Even though we have a longer growing season in Zone 7, the early spring can still be cool and wet. Winter sowing makes great use of those months and sets your plants up for strong growth when the soil warms. This can result in earlier blooms and harvests since your seeds will have sprouted by the time you would normally plant seeds in the ground. This low maintenance method of seed starting gives you strong seedlings that are already adapted to your local conditions. Winter sowing is also a perfect way to germinate those hard to start perennial seeds or any other seeds that need cold exposure to germinate.

Supplies You’ll Need

  • Clean plastic milk jugs or clear containers with lids

  • Potting soil (not garden soil)

  • Chosen seeds — look for “cold tolerant,” “hardy annual,” or “requires cold stratification”

  • Drill, screwdriver, or scissors (for drainage holes)

  • Heavy duty tape

  • Waterproof plant tags and garden marker

  • Spray bottle for watering

Step 1: Prepare Your Containers

  1. Clean the jugs. Rinse away any residue we don’t want nasty things growing in with the seeds.

  2. Cut the jugs. Slice horizontally around the middle, leaving the handle side attached to create a hinge.

  3. Add drainage holes. Drill 8–10 small holes in the bottom for water to escape.

  4. Add soil. Fill with about 3–4 inches of damp potting mix — moist but not soggy. This will help your seeds stay put.

Step 2: Plant Your Seeds

  1. Read your seed packets. Some prefer light to germinate, others need darkness. Make sure you know which your seed preferes. If it doesn’t say anything about needing light then you are okay to cover the seed with soil.

  2. Sow the seeds. I just sprinkle them on. No need to worry about spacing.

    • For most seeds, cover them with a thin layer of soil (about twice their size).

    • Press light-dependent seeds gently onto the surface.

  3. Mist the soil. Use a spray bottle to moisten without washing the seeds away.

  4. Label! Label! Label everything clearly. I can not stress this enough. You might tell yourself you’ll remember what seeds you planted but trust me you probably won’t. I like to place waterproof tags inside and write the plant names on the outside of each jug.

Step 3: Seal and Place Outside

  1. Tape along the cut. Use your tape to close it back up.

  2. Remove the caps. This lets rain and snow keep the soil moist without overheating. If you have a dry winter you will need to check the jugs and water when the soil is dry.

  3. Set them outside. Choose a spot that gets at least 8 hours of sun each day and is sheltered from the wind. You don’t want to have your jugs knocked over and things growing sideways.

Step 4: Let Nature Do the Work

Now comes the relaxing part. With everything prepped, you can step back and let nature handle germination. The freeze-thaw cycles of winter do exactly what your fridge “stratification” would do indoors, only better.

For the next several weeks, just give them a quick glance when you’re outside. If they start to dry out, spritz a bit of water through the open top.

Once you start to see tiny sprouts in March or so, open the lids on sunny days so the seedlings can breathe and grow stronger. By early spring, you’ll have jugs full of sturdy, ready-to-transplant plants — all from the comfort of your backyard.

With our mild but unpredictable winters, winter sowing brings color and life back to the garden months before most people start planting. It’s a wonderfully simple way to make the most of every growing day our Zone 7 climate offers.

Next week I’ll have a blog on winter sowing in ziplock bags for you.

Until then start saving those milk jugs and old bags — spring gardening season begins right now, in the middle of winter.

Seeds That Thrive With Winter Sowing (Zone 7)

Vegetable Seeds

  • Kale

  • Spinach

  • Arugula

  • Lettuce

  • Cabbage

  • Broccoli

  • Cauliflower

  • Swiss chard

Herb Seeds

  • Chives

  • Parsley

  • Cilantro

  • Dill

  • Thyme

  • Sage

  • Oregano

  • Mint

Perennial Flower

  • Echinacea (Coneflower)

  • Black-eyed Susan (Rudbeckia)

  • Shasta Daisy

  • Coreopsis

  • Gaura

  • Blanket Flower (Gaillardia)

  • Yarrow

  • Lupine

  • Verbena bonariensis

Annual Flower

  • Larkspur

  • Bachelor Buttons

  • Love-in-a-Mist

  • Calendula

  • Snapdragon

  • Sweet Pea

  • Strawflower

  • Stock

  • Cosmos (early sowing in Zone 7)

Potted Blossom