Milk containers make tiny outdoor greenhouses to start your seeds

Q. Someone told me larkspur, sweet peas and Shirley poppy seeds can be started outdoors in February. Is this true and are there any other seeds that can be sown outside this early in the season?

A. As you're flipping through the seed catalogs, it's inevitable that you start dreaming of your garden. It's also about this time of year we Midwest gardeners get excited about the growing season and want to start now. Well, you can!

Generally if a plant is considered hardy in your zone, you can plant its seeds during winter, no matter how cold it may be. This is often referred to as "winter sowing."

Some seeds considered hardy in our zone include most flowering perennials and hardy annuals. Seeds like black-eyed Susan, columbine, evening primrose, larkspur, bellflower, balloon flower and lupine. You might also consider winter sowing some vegetables and herbs such as spinach, kale, peas, oregano and cilantro.

A word of caution: If you have some tender annual seeds (impatiens, cosmos, zinnia, marigolds, carrots, basil, parsley) you may want to wait to winter sow those until late March or early April as their seedlings are easily damaged by frost.

Here are some tips for winter sowing.

Use this method to jump-start your garden outdoors, especially if your indoor space and sunlight is limited for seed starting.

Winter sowing uses typical household recycled containers such as plastic milk or water jugs, two-liter pop bottles and the like. They act as tiny greenhouses allowing you to sow seeds outdoors in February. Two key things to consider are that the plastic must be transparent enough to allow for sufficient sunlight and deep enough to allow 3 to 4 inches of soil and headroom for your precious seedlings.

Once you've identified the greenhouse containers, wash them using hot soapy water. Toss the lid as you won't need it. Using a utility knife or sharp scissors, safely create a hinged cover. Cut most of the way around the top of the container, leaving about a 1-inch hinge so that you now have a lid that can be lifted if you need to add water. Create some drainage holes in the bottom of each container. For a milk jug, make about 12 holes, some of them about a half-inch above the container's bottom and the rest on the bottom.

You're ready to add potting soil. Depending on size of container, you'll want to add 2 to 4 inches. Soak your soil and allow it to drain. If your soil isn't draining well, add some perlite. It will be important that you have good drainage once your seedlings are outdoors.

Pick your favorite seeds and sow them on the soil's surface. Smaller seeds can be sown directly on the soil's surface. Larger seeds like morning glories and sweet peas should be sown about one-eighth inch deep.

Also, be sure to label your greenhouses with a permanent marker so that you can easily identify which seedlings are planted where. Close the lid and secure it with some tape.

You now have greenhouses just waiting to produce new plant life for your garden! So, take your greenhouses outdoors. It is recommended that you set them on the south side of your home so that they get lots of sun and preferably offer them some protection from Old Man Winter's winds.

You're encouraged to house all of your greenhouses in a rectangular shallow plastic box (think under bed storage bin). This prevents them from being knocked over by the elements. Be sure to put drainage holes in the bottom of the bin as we wouldn't want the melting snow to flood your seedlings.

Put your patience hat on and wait for your seedlings to emerge. As spring arrives, your seedlings will show their faces. At this point, begin to manage their water supply. You can open your hinged-top and moisten your seedlings if the soil is dry. Throughout spring, give your seedlings some fresh air during sunny days and close them up as dusk arrives to protect them from cool spring nights. In no time at all you'll have strong seedlings that can be transplanted in your garden.

­- Wendy Reiner

• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines, and University of Illinois Extension, North Cook Branch Office, Arlington Heights. Call (847) 298-3502 on Wednesdays or email northcookmg@gmail.com. Visit web.extension.illinois.edu/mg.