What Is Winter Sowing?

Using commonly recycled containers and a few hardy seeds, you can make your own mini greenhouses

It’s finally December, which for many means hosting parties for family and friends, removing snow from driveways and serving platters stacked high with sweets. While all of these can be wonderful aspects of the season, avid gardeners may find themselves counting down the minutes till spring, eager to return to their beloved beds.

Sure, determined gardeners can keep houseplants and start seeds indoors, but for those with limited square footage, finding enough space for all their flowers can be challenging. This limitation paired with the harsh conditions outside can leave gardeners feeling helpless. Fortunately, there’s a way to sow seeds outdoors in the winter, using just a few commonly discarded containers.

What Is Winter Sowing?

Winter sowing is a process by which a gardener plants seeds in empty milk jugs, thereby increasing their chances of surviving the cold weather. The milk jugs act like mini greenhouses, trapping heat and protecting the seeds. With this method, you’ll never have to dig holes in the cold, frozen soil again!

What Are the Best Seeds for Winter Sowing?

Technically, both perennials and annuals can be winter-sown, though cold-hardy seeds will yield the best success rates. Check seed packets for phrases such as “self-sowing,” “direct-sowing,” “cold hardy” or “pre-chill” to determine if the seed can be winter-sown.

When Can I Start Winter Sowing?

When to begin winter sowing depends on two factors: where you live and what you want to grow. Please note that winter sowing is most effective for gardeners in zones 4 through 8.

In general, winter sowing can be started anytime from the Winter Solstice (now) until a couple of weeks before the relevant zone’s last frost. The specific timing depends on the needs of the individual seeds selected.

Seeds that require long germination periods, like flowering perennials, winter vegetables and native shrubs can be sown right away (December and January). Cold-hardy perennials and annuals will typically be best sown in the first months of the New Year (January and February). Tender annuals that require more consistent warmth are best sown just before the last frost (March or April).

How Do I Make Containers for Winter Sowing?

Variety of plastic bottles protect the seedlings in an outdoor gardentanyss/Getty Images

To begin winter sowing, you’ll need a few materials to create your containers:

  • Milk jugs (one per plant type)
  • Scissors, box cutter and/or Exacto knife
  • Drill (optional)
  • Water
  • Potting mix
  • Seeds
  • Duct tape
  • Permanent marker

First, clean the jugs and cut them in half below the handle to create a bottom and a lid. If desired, you can leave a “hinge” piece of plastic uncut beneath the handle. Drill or cut drainage holes into the bottom of each jug and remove their caps.

Moisten the potting mix so that it just holds into a ball when packed. Fill the bottom of the jugs with four to six inches of the moistened potting mix. Sow the seeds in the potting mix as instructed on the seed packets. Use only one seed type per jug and space them appropriately.

Now, reseal the jug shut with duct tape, and label each jug with the plant type and date of sowing. Place the jugs outside in a sunny spot with low wind.

How Do I Care for My Winter-Sown Plants?

As with regularly sown seeds, winter-sown seeds must be monitored to ensure their health. Check regularly to make sure the potting mix stays consistently moist and water the plants as necessary. If the seedlings start to look scorched, move them to a location with partial sun. Don’t worry too much about snow or rain; snow can provide welcome insulation and rain will save you a day of watering.

Once the seedlings have a couple of sets of mature leaves and the weather warms, it’s time to start hardening them off. Either drill extra ventilation holes in the top half of the jugs or open them during the day. (Depending on your conditions, they may need to be closed at night.) If the seedlings grow crowded, thin them out by moving them to other sheltered containers.

What Do I Do When Spring Has Finally Sprung?

By the time spring arrives, hopefully, you will have a lush milk jug garden of seedlings. Now you can simply use the guidelines on the backs of the seed packets to transplant your seedlings into your main garden. While you’re at it, complete a few more off-season gardening tasks and give yourself a pat on the back for a successful sow!

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