Living where we do gardening can be a challenge. As I write this it is March 25 and we have 10″+ of snow in many spots still. Our growing season normally starts May long weekend but with greenhouses and cold frames we get things started earlier. Late October is usually a safe bet on harvesting your root veggies although I just pulled an arm load of onions we missed out of the tiny bare patch of my raised bed today (Even though my kids said they got them all I thought their haul looked a bit on the light side). So that being said we mainly get June-Sept as our best growth months. Anything later than that will be Russian kale, chard, radishes, certain salad greens like mesculin and root veggies but growth rates are near nil.
While doing my silviculture work I was taught that the tree planters will often try to find a raised planting location as the higher parts of the terrain will melt off sooner than the lower spots (This is why I got some onions today, my raised beds are starting to show in the snow). The result is a 25% longer grow season for the trees. Another trick is to plant the seedlings near a heat sink such as a rock, log or stump. This gives them extra warmth nearby to help them through the cold nights after being planted. We also look for ideal soils to put them into but in your home garden this should be already taken care of, I try to remember all these techniques when doing my own home gardening.
When planting out my spaghetti squash seedlings I will put them beside a hunk of firewood. I start them early indoors in a window mounted cold frame. I can leave the window open a crack to keep them warm and they love it. I did an experiment a few years ago and put some out with and without a heat sink and only the ones that had the heat sink survived the cold nights. This practice adds a couple weeks to my season.
Even in my greenhouse I will grow my first batch indoors and plant out when the soil just gets warm enough. Being that seeds often need 22C/70F or warmer soil temperatures for germination, I like to get a jump on it. That way I can enjoy my pak choy and cos that much sooner.
Looking inside my greenhouse today I see that some of the seeds of my red orach plant have already volunteered to germinate. I guess I should have collected my seed last fall haha. ~Scott