How to Winter Sow Wildflowers

winter containers outside
Lined up in a partial sun area, these containers are patiently waiting for spring.

As part of my big project for 2013, I’ll be using winter sowing containers to grow several kinds of wildflowers from seed. Wildflowers lend themselves very well to winter sowing because many of them require cold stratification, which is a period of chilling prior to germination.


For winter sowing, you need the following items:

Clear plastic containers, at least 4 to 6 inches deep. (I like gallon milk jugs, but some gardeners swear by those large lettuce or spinach containers or 2-liter soda pop jugs.)

Potting soil (Your choice on brand and type. This year I am using a homemade mixture of two parts each peat moss and vermiculite and one part worm castings. This is a recipe I picked up from one of my favorite garden blogs. You have to listen to the podcast to get the full recipe, but it’s basically 2-2-1.)


Equipment to poke holes in and cut plastic jugs (such as scissors, awl, pruning shears or soldering iron)

Duct tape

Markers, something to write on (popsicle sticks, old blinds, etc.)


1) Wash the containers well in a 10 percent bleach solution. Rinse.

soldering iron
A soldering iron makes quick work of creating drainage holes in the winter containers.

2) Poke several holes in the bottom of the container for drainage and a few in the top to allow rain or snow to drip in. I’ve used scissors in the past, but after seeing a recommendation here, I bought a cheap ($4 at the local big box) soldering iron, which is a breeze for poking holes. Be aware, however, that melting plastic stinks. I do this on the back patio. Also, be careful if you have children in the home — soldering irons get really hot!

container hinged
Container ready for soil and seeds.

3) Cut around the jug about 4 to 5 inches from the bottom, leaving the handle in place, so it functions like a hinge. For this, I poke a hole in the plastic with a pruning tool, then cut around with a scissors.

4) Put your potting mix in a large bucket and get it very wet. Give the water time to soak in, so you are sure you have a good, loose, wet soil.

5) Prop open the container and fill it with several inches of soil. Pat this lightly, then plant the seeds according to package instructions. Some seeds need to be immersed in the soil, others can just float on the surface with a little soil on top.

6) Write the name of what is in the container on a plant stick using a grease pencil (if you can find one) or a permanent marker. Also, write an identification on the outside of the container as well. DO NOT SKIP THIS STEP. You will forget what is in the container, if it is not marked. This year, I numbered the containers in multiple spots and lined them up in order, as a back up in case my markers fade.

7) Once they have been thoroughly marked, seal up the containers with duct tape. Some gardeners leave the caps on the jugs, some don’t. I have a few of each.

8) Set the containers outside and wait. As spring arrives, you will need to check the containers regularly to make sure they have enough moisture. When plants start to grow, gradually make the air holes on top larger and eventually cut the tops off the containers. Here’s a good video that shows you how the seeds will progress.

9) When you seedlings are strong and the weather has warmed up, plant them in the garden and enjoy.

The Meadow Project

meadow 2011
This is the area I’m hoping to improve this year, with more wildflowers and native grasses.

The biggest garden project I have planned for 2013 is to plant more prairie-style plants in the meadow behind my house, which runs adjacent to a city-owned walking path. While I planted wildflowers in it when we first moved out here, this area has become overrun with wild parsnip, giant ragweed and a few other real bad-boys of the plant world. I’ve undertaken some steps to remove the invasives and plan to replace them with grasses and wildflowers native to Minnesota. My hope is that this area will provide lots of nectar for butterflies and bees, seeds and nesting sites for birds and beauty for all the humans that pass by it each day.

I’ve ordered both plants and seeds from Prairie Moon Nursery in Winona, which is one of several outstanding native plants nurseries in our area. Why order both plants and seeds? Insurance — plain and simple. The plants will come in May, all ready to grow, having been started and nurtured by the pros at Prairie Moon. That’s great, but the plants are not cheap. Seeds, on the other hand, are cheap, so I’m hoping to get more plants at a lower cost by growing some myself.

sunflowers in meadow
Sunflowers have done well in my meadow, but I’m hoping to add greater variety of native plants.

Since most wildflowers require what’s called cold stratification, winter sowing is the perfect method for starting wildflower seeds. Cold stratification means that the seeds need to experience the cold of winter before they will germinate. I put out a call on Facebook for some milk jugs to use for winter sowing, and so far — thank to my friends Betsy and Marcia — I have about 25 jugs.

The idea behind winter sowing is that you create a little greenhouse for the seeds, by filling the milk jug with very wet potting soil, planting the seeds, sealing it up and putting it out in the cold. The seeds will freeze and thaw and refreeze as the weather moves from winter to spring. Eventually they will start sprouting, at which point you begin exposing them to more air and opening up the little greenhouses.

Tomorrow I’ll write more about how to set up winter sowing containers. Here are the seeds I’ll be starting in my containers:

Golden Alexanders (Zizia aurea)

Foxglove beardtongue (Penstemon digitalis)

Sweet Joe Pye weed (Euptorium purpureum)

Short’s aster (Aster shortii)

Nodding onion (Allium cernuum)

Butterfly weed (Asclepias tuberosa)

Rattlesnake master (Eryngium yuccifolium)

Common ironweed (Vernonia fasciculata)

White prairie clover (Dalea candida)

Spotted beebalm (Monarda punctata)

Meadow blazing star (Liatris ligulistylis)

What are your favorite prairie plants?

Wildflowers of Minnesota

A Gardener’s Reading, 10 of 30

By Stan Tekiela (Adventure Publications, 1999)

This wildflower guide is one of several by Minnesota-based naturalist and photographer Stan Tekiela. (The bird and mammal guides are great for nature watchers.) In this guide, Tekiela identifies about 200 Minnesota wildflowers, giving information on how and where they grow, what their leaves and flowers look like, and how they might (or might not) be useful to home gardeners.

The book is organized by flower color, which is helpful since color is one of the easiest things to notice in a plant. But beyond that, Tekiela shows how the leaves are arranged and describes where you are most likely to find the plant in the wild. If it showed what the plant looks like when it first emerges in the spring, it would be the perfect wildflower guide.

For gardeners, it has some special uses. For instance, it was with this guide that I first identified wild parsnip growing in the meadow area behind my yard. An invasive, wild parsnip is pretty in its way—with yellow up-facing broad flowers—so knowing this one will take over was helpful, and sent me on a wild spree of pulling the stuff from the meadow. (Be sure to wear gloves; it can sting the skin.) It’s also useful for determining which natives might have a place in your garden. From spring ephemerals, such as pasque flower, to big prairie plants, like common sunflower. From a more intellectual perspective, I enjoyed looking through the book to see how the characteristics of plants from the wild have been transformed by breeding into the garden plants we know.

If you live near or like to visit wild places or just have a love of native plants, Wildflowers of Minnesota is well worth having in your library.


Persistent Plants: The Downside

Blue forget-me-nots

Shortly after posting the item on an amazing tree that clings to life from the cliffs at Pictured Rocks National Lakeshore in Michigan, I got to thinking about another aspect of persistent plants: the invasives. These, too, find homes on the sandstone cliffs off of the south shore of Lake Superior — and once they’re established they don’t want to go away.

Clintonia borealis
Miner's Castle on Lake Superior

While visiting Miner’s Castle (photo below), we admired the pretty forget-me-nots (Myosotis spp.), blanketing the forest floor nearby. It turns out these are not natives to the area, but a very aggressive plant that is displacing trout lilies and other plants of the region. Since this is a rare ecosystem, the National Parks Service is taking some steps to remove (or at least reduce) the forget-me-nots and other invasives such as garlic mustard and spotted knapweed from the area. We also saw what I think is Clintonia borealis (yellow corn lily), which is native to the Upper Penninsula.