With the sudden spike in temperature expected over the next three days, I might just have left it a little too late to start sowing these lettuce and salad seeds I’d been saving — samples received through my membership in the Garden Writers Association.

I hope not. I’ll be squeezing the seeds into some of my containers, and trying to space out successive plantings to get a staggered harvest of salad stuff before the really hot weather becomes the rule rather than the exception.

Lettuce, like a lot of leafy vegetables including spinach, cabbage and kale, is a cool season crop – meaning it can be seeded before the last frost (and leaf lettuce can also be started again as the weather cools down in the fall).

In fact, all these leafy greens are just waiting for warm weather to bolt, turning all their energies away from producing leaves for your salad, and into sex. That is, the making of babies aka seeds. Not only do they shoot up their flower stalks when it’s hot, the heat makes the few remaining leaves taste tough and, worse, bitter.

Peas also prefer a cool start. Root vegetables such as carrots or radishes, too. As a matter of fact, you can sow these last two in the same row to save space — the radishes germinate and ripen quickly before it’s time to pull the carrots. Beans, on the other hand, like the soil to be warm, and should be planted after any threat of frost*. For a good overview on planting and growing conditions for different veggies, check out this guide from the University of Massachusetts.

*According to the handy frost guide in my new Toronto Gardener’s Journal, the weather in Toronto proper is (statistically) frost-free from now on – a whole month earlier than the Victoria Day long weekend we’ve traditionally considered planting day. You might want to be circumspect when planting out tender tomato or eggplant seedlings, though, keeping an eye on the weather reports for freezy night temps or early morning frosts. Protect your babies overnight by covering them up if the reports look grim.

I wish I could grow more vegetables. Nothing beats the sweetness of a garden-fresh beet or carrot. The biggest gardening mistake my husband and I made was to give up our allotment garden at the foot of Leslie Street after we bought our first house more than twenty years ago. It took me only one season to realize that sun trumps shade when growing vegetables, and I’ve been regretting our decision ever since. My garden doesn’t support much more than herbs, and a grape tomato in a pot.

But, who knows, maybe this year I’ll have salad greens. What are you planting in 2009?