These Seeds Can Be Sown in the Dead of Winter - Even in Snow - for Jaw-Dropping Spring Blooms

Spring fever can hit when there’s snow on the ground and the mercury drops, so don't put off your gardening plans. Winter can be a great time to plant.

Many gardeners start seeds indoors for a headstart on the growing season, but that can be tricky, especially if you don’t have much space or light. Instead of struggling with varieties that just won't sprout, or a few spindly seedlings that do pop up, follow Nature’s lead instead, and try winter-sowing.

What is Winter Sowing?

Winter sowing is an easy way to start many kinds of seeds outdoors. Don’t worry that they'll freeze; many varieties won’t germinate at all unless they’re exposed to freezing or extremely cold temperatures.

Winter sowing refers to planting cold-hardy annual, perennial, native or wildflower seeds that need a “chill period.” Sometimes this is called stratification, but it's not quite the same thing. Stratification uses cold temperatures and a damp or dry medium to trigger germination, like the practice of storing seeds in a refrigerator. Winter sowing means planting seeds outside in the cold and letting nature do the germinating.

What is a "Chill Period"?

"Chill period" refers to how long seeds need temperatures from about 32 to 41 degrees F. to break dormancy. Different varieties need different amounts of time. Most coneflowers (Echinacea), for example, need a chill period of 4 to 12 weeks, while columbines (Aquilegia) need about a month.

You’re mimicking nature when you winter-sow, because you’re letting seasonal conditions like freezing and thawing start your seeds. You can winter-sow in containers or directly in the ground, as long as it’s not frozen. But wait until after the first hard freeze, and until nighttime temperatures are consistently below 50 degrees F. You don’t want seedlings to sprout in a warm spell and perish in the next deep freeze.

Read your seed packet to find the chill period for each variety. If it's not specified, look for terms like “cold-hardy,” “sow in fall for spring germination,” "self-sows," "hardy" or "pre-chill," or do a little research. You can winter-sow many flowers, herbs and vegetables, but we’ll focus on flowers here.

Why Winter-Sow?

Unlike starting seeds indoors, winter sowing doesn’t take up space in your home, and you can do it outdoors in containers, the ground or raised beds. You don't need lights, heat mats, circulating fans or supplemental watering, so you save on buying equipment and paying utility bills. Since the seedlings will sprout outside, you don’t have to harden them off before you transplant them. They’ll already be acclimated to the outdoors and more likely to survive and thrive.

How to Winter Sow in Containers

Clean, used milk jugs are great for winter sowing, because they work like mini-greenhouses. So do large plastic soda bottles, take-out food containers and other deep containers with lids. They should be clear or only slightly opaque, so the seeds get sunlight, and you can watch them grow. Poke holes in the bottoms of the containers for drainage and in the tops for ventilation.

If you use milk jugs, cut all the way around them, leaving about an inch under the handle still attached. This creates a hinge, so you can flip the top open and shut. If the jug has a handle, make the hinge under it so it's easy to move around.

Fill the jugs or other containers with 2 to 4 inches of moist potting mix. Sow the seeds as directed on their packets and water them gently. Stick to one species per container, to avoid confusion. Recycle the milk jug caps; you'll leave them off, so air and water can get in.

Seal the containers with duct tape, so the tops won't blow off, and label them with the kind of seeds and the date. Laundry markers are good to use for long-lasting labels.

If you’re in a cold climate, put your containers in a spot that gets some sun and moisture from rain or snow. If your climate is mild, give them some shade so they won’t overheat. Place them on the ground or on an outdoor table, low wall or shelf to keep them away from foot traffic, wildlife and pets.

Check the containers often and, if necessary, make more holes to improve air circulation and let excess moisture escape. Water when needed so the soil doesn’t dry out. You can open the containers on warm days to let the seedlings get used to the early spring weather, but close them at night. Transplant them when good root systems develop.

How to Winter-Sow in the Ground or Raised Beds

Winter sowing directly in the ground or raised beds is even easier than in containers. Wait until you can work the top couple of inches of soil and it's not too wet, so the seeds won’t rot. In many USDA Gardening Zones, winter sowing is best done from late December (if your soil is cold enough to keep the seeds from sprouting too soon) into January, February and March.

Add some potting soil to the ground or raised bed and sow the seeds as directed on their packets. Water them gently. Thin the seedlings if they come up too close together by following the spacing directions on the packets. Use plant markers to remember what you sowed, and where. Emerging seedlings can be hard to tell apart.

What Kinds of Seeds Can I Winter-Sow?

You've got lots of choices for winter-sown flowers. Try cold-hardy annuals like snapdragons, sweet peas, calendulas, cornflowers, larkspurs, sweet alyssum, Nigella (Love-in-a-Mist), pansies, violas, phlox, poppies and bachelor’s buttons.

For perennials and natives, choose coneflower, foxglove, columbine, yarrow, penstemon, bee balm, delphinium, lupine, black-eyed Susan or brown-eyed Susan, Angelica, Liatris (also called Blazing Star or gayfeather), butterfly weed, ironweed (Vernonia fasciculata), Joe Pye Weed, Kiss-Me-Over-the-Garden-Gate (Polygonum orientale), Lobelia, milkweed and primrose.

Need ideas for winter sowing veggies and herbs? Try leafy greens like spinach and lettuce, root crops like radishes and beets and herbs like parsley, cilantro and dill.