Margaret Lauterbach

Here comes the sun: Time to get our cool-weather plants outside

It is the season for sowing hardy cool-weather crops and transplanting those seedlings that shrug off frosts. We’re not frost-free yet. The average date of last frost here is about May 10, but if you’re planning on setting out tomato or pepper seedlings, wait at least until the snow has melted off Shaffer Butte, a location visible from Downtown Boise. Those and eggplant seedlings, sweet potatoes, squash, melons and beans are easily killed by frost.

Be sure you harden off your seedlings before transplanting items such as lettuce, spinach, Swiss chard, cabbage, kale, collards, broccoli and Brussels sprouts. That is the best way to acclimate plants to wind, sun and other aspects of harsh weather. Unless this acclimatization is gradual, sudden exposure to full sun may destroy the chlorophyll in leaves, killing the seedling. Don’t count on sunlight coming through window to harden them off, for glass filters out part of the sunlight. In full sun, the leaves just bleach white, and they’re goners.

To harden off seedlings, put your seedlings out in dappled shade for lengthening periods of time, then expose seedlings to early-morning and/or late-afternoon sun before exposing them to full noon sun. This should take several days, unless we have some overcast drizzly weather that is perfect for transplanting. So perfect for the plants that even gardeners rejoice, even though we might be wet, cold and miserable. In the past, I’ve transplanted out on such a day after just two or three days of standard hardening off without killing my seedlings. You’ll get the best results if your soil is at least 60 degrees. If you can’t take that much time to harden off your seedlings, at least put them in dappled shade where they receive full sun in morning or afternoon, and in a day or two, begin leaving them out overnight. On the weekend, you can expose them to full overhead sun for a limited time before putting them in a full-sun location in your garden bed.

When sowing seeds, plant to the depth recommended on the seed packet. If seeds are tiny, just distribute them on top of moist soil as best as you can. Frankly, I think it’s a good idea to cover them with something like a slender board (a 1 x 2, perhaps). I do use one when I sow carrot seeds on top of the soil. It may take carrot seeds over two weeks to germinate, and the narrow board holds moisture and presses the seeds against soil. Lift the board once in a while after a week, and when you see signs of germination, remove it.

Newly germinating beet seedlings are dark red in color and hard to see for us gardeners, but birds see them and eat them greedily unless we cover the area in which we’ve just planted beet seeds with something like floating row cover.

All germinating seeds must remain moist, but never wet. Wet conditions will drown and rot them. Remember that seeds are living things. Seed coats enclose an embryo with sufficient food to get it started. Many seeds have a coating that protects against premature germination that would compete with parent plant or siblings, so that coating must be removed or disabled before your seeds can germinate. (The exception is a few modern varieties germinate inside the tomato, a situation known as vivipary.) Tomato seeds, for example, can be germinated (usually) only after a winter’s exposure to snow, cold and/or rain or if you’re saving your own seeds, after some fermenting. To save your own tomato seeds, squeeze or spoon seeds into a bowl, add water, and let them sit for a few days, stirring occasionally, until some mold appears on top. Then dump contents into a sieve and rinse, and dry seeds on china or plastic for easy removal and storage.

Parsley and its variations such as chervil and parsley root may be hard for a gardener to germinate, but it’s easier if you soak the seed for 24 hours, thus destroying the anti-germination coat, before sowing it. Traditional lore is that parsley is slow to germinate because it has to go to the devil and back before it sprouts. Parsley and chervil reseed themselves in my yard, and wherever they germinate they’re welcome.

▪  Speaking of saving your own seeds, I recently learned that the “doomsday vault” of stored seeds is in danger of flooding because Arctic ice is melting faster than expected. I think some water seeped into that vault at Svalbard, Norway, last year, but the gardening world was assured no seeds were damaged or destroyed. That Global Seed Vault, intended to preserve seeds in case of a global calamity, now is at risk because warmer temperatures are melting snow and ice so fast that it’s reducing glare, so melting much faster than expected.

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