Margaret Lauterbach

Learn about starting seeds indoors and vernalization while spring is far off

You could start seeds indoors now if you wish. I’m starting onion, leek and shallot seeds, but won’t put them in the ground until about April. I’m also starting tronchuda, kale and collards that can be put in the ground in late February or March. We used to wait until St. Patrick’s Day, but warmer temperatures are too tempting.

Other seeds that may be sown this early are celery and eggplant, because they’re slow-growing seedlings.

If you’re growing on a windowsill, be sure to turn your plants every day or two to keep them from permanently leaning toward the sun. Be sure you have in hand all of the varieties of seeds you’ll want to grow or know where to get them locally. Good varieties do sell out fast.

Cold weather affects seeds quite differently. Some require cold to break dormancy so they can sprout and grow. This is known as “stratification.” Seed packets of many flowers specify the need for this cold stratification, which you may achieve in your refrigerator. You can also achieve this by “winter sowing,” planting seeds in fall or later in winter (such as now) and letting the cold winter temperatures work to break dormancy. If you sow seeds now for stratification, it’s a good idea to shelter seeds from hungry birds or rodents.

Some folks cut three sides of a plastic milk jug about 3 or 4 inches from the bottom, for instance, and after making drainage holes, they tip the top back (the uncut side acting as a hinge), put a layer of potting soil in the bottom, dampen it, and strew seeds on top – lightly covering them before fastening the jug back together with duct tape. The jug top is left open, so there’s some evaporation of moisture and release of heat. You should check for continued dampness of the seedbed occasionally until germination, at least.

Seed packets or reference books that advise cold stratification for seeds almost never tell you that those seeds should be included with planting soil for that cold treatment. But they should tell you that.

▪  Vernalization is what we’re doing now. That is, we’re winterizing ourselves. This is a term that’s useful in gardening, for several reasons. One is that vernalized biennials such as carrots, onions, celery, and many other common vegetables and ornamentals go to flower and seed their second year. Sometimes we accidentally vernalize our plants, planting them before cold weather has passed. It’s especially annoying when bulb onions send up flower stalks, destroying the bulbs they’re growing from.

Vernalizing is useful, though, for some food crops that need a cold spell before they produce something such as Romanesco broccoli/cauliflower. Some seed vendors call it a broccoli, others a cauliflower. The texture of the head is closer to cauliflower than broccoli. This wonderful chartreuse-colored rococo vegetable, a pyramid of Fibonacci swirls and mini-pyramids, needs to be vernalized before setting a good head. The newer hybrid versions have been a disappointment in my garden, sending out leafy sprouts in the middle of that lovely granular head, spoiling its nutty flavor. I’ve never seen seed vendors’ advice for the need of vernalization of this brassica, but ran across that advice accidentally last week.

Indicating the truth of that requirement, a few years ago I grew lazy about garden cleanup and left some cole crop plants in the ground. Frosts and even some freezes are tolerated by most kales, collards, cabbages, etc. There was a large cole plant I looked into on Jan. 1 that winter and found a beautiful head of Romanesco. We had had several frosts and freezes, but it sat wrapped in leaves, a perfect and beautiful vegetable.

You may be able to fudge a bit with this plant, starting it indoors and then putting it in a fairly sheltered location outdoors as a seedling, weathering more wintry weather for three to four weeks before transplanting in soil. I’ll try it this year, and let you know if it works to produce a good head. The basic open-pollinated Romanesco broccoli is a very large sprawling plant, taking up about a square yard to produce a nice head. If we can produce it earlier, the plant will likely be smaller than that nonhybrid version I found that New Year’s Day.

Unsettled weather such as a cold period in spring may vernalize plants in your garden that you don’t want to be vernalized. Most brassicas and alliums, for instance, are biennials, and once vernalized they’ll go to flower and seed. In the case of brassicas, the flowers are edible, but in the case of the alliums, it often destroys their usefulness as food. Flower stems arise from inside the bulbs or white parts of onions and leeks, so that they’re destroyed by the tough stem and the efforts of the surrounding layers to feed it.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.