Saturday, March 6, 2010

In the last issue I mentioned a method I use for growing perennials from seed called “Winter Sowing.” As the name implies, now is the time to employ this technique.

Winter sowing works like a charm for most perennials that will reseed themselves naturally. At the same time it offers control that the gardener would not have if he were to simply throw seeds out into a garden bed. The basic idea is that the seeds of many cold hardy perennials need a period of cold in order to germinate (stratification.) Here you will be giving the seeds the conditions closest to how Mother Nature would do it all on her own, without risk of the seeds being lost to foraging animals or being washed away in a heavy rain.

To begin you need seeds. This time of year you almost have to order them through the mail. I have a couple favorite sources you can check out. Johnny’s Seeds ( is my go-to company for anything gardening related, and perennial seeds are no exception. If they don’t have what I’m looking for, I will try Select Seeds (, which has an awesome selection of unusual, and heirloom varieties. One very important factor that I look for when choosing a mail order source for plants is that the company is based in the Northeast. I’m really not interested in plants from California. Johnny’s is in Maine and Select Seeds is in Connecticut.

Next you need containers in which you’ll plant your seeds. Just about anything with a clear plastic cover will do. My favorites are those salad containers from McDonalds or Wendys with the black bottoms and the clear domed lid. You can also use milk jugs or soda bottles. For those you slice the jug in half horizontally, leaving just a hinge uncut, so that you have a 3-4 inch base to fill with soil. Then you can duct tape it back together later.

And finally, you need soil. This is easy; just about any bagged potting soil will suffice. You just don’t want regular garden soil as it will likely contain too much clay and will compact to a point that you will lose maximum germination.

Now you need to create drainage and ventilation in your containers. I have an old knife that I heat up on the stove to make nice slits in plastic containers. Slice drainage holes in the bottom of the container you are using, and a few holes in the top. If you are using milk or soda bottles the open mouth of the bottle is enough ventilation and you do not need to cut any additional holes.

Make sure you label your container with the name of the plant you intend to plant in it; Sharpie marker on duct tape on the bottom of the container holds up well. Then fill the container with soil and moisten it well. Let the excess water drain and plant your seeds. The seed packets should include instructions on how deep each seed variety should be planted. Regardless, a good rule of thumb is to plant the seed twice as deep as the size of the seed. Hence, a very large seed such as 4 O’clocks would need to be planted about ½ inch deep, whereas some very miniscule seeds may just need to lay on the surface.

All you do next is put your containers outside in a shady spot. Let the snow cover them and forget them for the next couple months. Once April comes around and the snow has receded you’ll want to start checking them to make sure they don’t get dry but it will be a surprisingly long time before you see any seedlings emerge.

Once you do see seedlings (likely not until late May and well into June) you will need to pay closer attention to the containers. Keep them in the shade or the sun will fry the tender seedlings. Take the lids off during warm days to prevent the mini-greenhouse from overheating and be sure to put the lid back on during cold nights and heavy rains.

When the seedlings have a set or two of true leaves (as opposed to the cotyledons which appear first) you should transplant them individually into a bigger pot. I like to use empty yogurt containers with drainage holes punched in the bottoms. This is the most tedious part of the process and should not be attempted on a day when you have little time or your patience is not at 100%. Often the seedlings will be close together and need to be delicately teased apart. If they are too thick to separate easily, take a spoon and plant a hunk of seedlings together in one pot. Later you can thin them down to just one in the pot.

After that you just let your new young plants reach a good size, start putting them out in more sun to harden off and plant in your garden beds. I have found that these plants are stronger and hardier than greenhouse grown plants. Some examples of plants that I have had fantastic luck with growing from seed in this way are Delphinium, Foxglove, Rudbeckia, Echinacea, Columbine, Rose Campion, Penstemon, Balloon Flower, Dianthus, Baptista, Heliotrope, and Monkshood.

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