Gardening: Winter in Boise means sowing seeds in containers and watching the weather

The good news is that the daylight hours are getting longer, little by little, and in less than a month we’ll have sunlight for more than 10 hours each day, a magic figure for plant growth. Remember, though, the calendar says we’re in winter, and we have been for less than a month, even though our gardens have been put to bed since October. My garden beds are blanketed with fallen leaves for the duration of winter.

Many folks are new to this area — most from Washington, Oregon, Colorado, Arizona or California — and don’t know what weather to expect. The climate is changing, but in the past we have had some severe cold in January and February, a January thaw, and bone-chilling winds in March and April. Since we’re not out of danger for freezing weather, most of us wait until late February or early March for most of our dormant wood pruning.

If you severely cut a shrub or tree back, and then freezing weather arrives, it may damage that tree or shrub beyond your cutback, and could even kill it. Pruning delay removes this threat. Vines such as grapes are very tough and resilient, so in our area we usually prune table grapes, at least, in February. I think they prune dormant wine grapevines when they can.

It’s a little early now to start your garden seeds, unless you do some winter sowing in containers. Most folks use large clear or opaque plastic containers with drainage holes added, and cut off three quarters around so that the container can remain intact, the upper part bent back to insert planting soil, seeds and water. Once planted, they then restore the upper part and secure with something like duct tape.

It’s far too early to start fast-growing vulnerable plants such as tomatoes or peppers, but cole plants such as cabbage, kale, broccoli, collards or cauliflower can tolerate frost. You’ll have to check to maintain moisture in your containers, and you may have to cover them to protect from severe temperatures. There are explicit directions for sowing specific crops via Google and/or YouTube. If you’ve started plants in a cold frame, don’t forget to open it on sunny days, closing it at night to prevent damage or loss.

Some ornamentals and seeds for fruit trees such as Pawpaws must be subjected to cold temperatures for various durations before they’ll germinate. Winter sowing does that for gardeners, and it’s easier than remembering to extract a bag of seeds and planting soil out of the refrigerator in time for sowing. Some seeds must be subjected to high temperatures before germinating, and still others must be regularly washed to eliminate germination inhibitors. A clever friend placed the latter kind of seeds in the tank at the back of a toilet, so every time it was flushed, the seeds were dipped into and out of the water.

Winter sowing of Romanesco broccoli may be just the right way to grow that delicious crop, since it needs to experience cold, frosty weather to form its grandiose, rococo head. It has a delicious flavor, but is not colored the deep green that spells healthy nutrients like regular broccoli or Piracicaba have.

If you haven’t grown Piracicaba before, it was conventionally bred — not GMO — by Brazilians (and named for a river in the vicinity of their test fields) to produce broccoli in hot weather. It doesn’t produce a large head, but many side shoots. The more you pick, the more you’ll have to pick, since picking clusters of buds stimulates bushiness, more bud clusters forming on new branches.

I wouldn’t advise sowing seeds of biennials such as carrots, onions, leeks or cole crops yet, for the cold weather we expect may fool those plants into thinking they’ve gone through an entire winter, and are ready to blossom and set seeds. Once onions set seeds, the bulb is no longer good for kitchen use. My attempt to transplant carrots resulted in very short, stumpy carrots. I don’t recommend that.