It's getting to be time to start moving your pampered seedlings outdoors. These seedlings are used to all the luxuries of life under lights or in a greenhouse: warmth, controlled lights, regular water and feeding. As we've all had to learn, life on the outside isn't that pampered. To avoid sending your seedlings into transplant shock, you need to acclimate them slowly to the harsh realities of garden life by hardening them off. It only takes a few weeks, but it will keep your plants growing happy, rather than stunting them with a sudden chill.
One of the best ways to harden off plants is with a cold frame. You can build a quick and dirty cold frame with hay bales or cinder blocks and a cover. But purchased models really aren't that expensive and will last you for years. If this is the year you take the plunge, here are some noteworthy cold frames to consider.
Photo: © Marie Iannotti
Comments
I thought I’d try a little tough love and put some of my seedlings outside in my mini greenhouse that I setup on the flagstone patio. I planted them too early I think because they are getting huge and are taking over the house. Unfortunately they didn’t survive the night. Thankfully I only put out a sample of each type of plant. We are zone 3 here in Calgary and I wasn’t sure if it was too early or not but thought I’d sacrifice a couple of my babies just to see since I’m running out of room for them in the house. I’ll try again in a week or two. The pansies I planted outside a couple of weeks ago are hanging on valiantly despite the bits of cold but then I guess they are hardier. I do envy those of you that are able to get an earlier start on your gardening. But, I’m still enjoying the springlike weather and getting things ready to go so it’s not all bad. Happy gardening!
I start my seeds in our heated basement. The basement is kept at 68º until the seedings have their first true leaves. I then gradually lower the temperature over the next couple of weeks until it is 50º. The plants are then hardened off and ready to be planted.
Lynne, I’m having just the opposite problem. The temperature went from the 40s to the 80s. The lettuce I put in my cold frame is totally confused. If it’s not one thing, it’s another.
Sharon, that’s very clever. I wish I could control the temperature like that. My basement is not heated, but it does heat up under my plant light. Unfortunately, there’s no way for me to lower the temperature without losing the light.
Sharon, I am totally jealous that you are able to control your basements temperature. From what I read in a plant propagation textbook, that’s exactly how they do it in commercial greenhouses. Marie, I was gonna suggest a small window unit air conditioner, but its a basement, you might not have windows. Silly me. Maybe a combination of fans/cooler bulbs might do the trick???
Lynne I know how you crowded you feel about now. Gotta hand it to ya in zone 3. Im whiny in zone 5! I did the same exact thing last year and killed most of my dwarf zinna. Luckily 2 lived and now i have tons of seed. I’ve tried covering a very small cold frame overnight with a wooden an a blanket, and it didn’t save the heat at all. It looks like a small greenhouse heater would be the most effective way to get the temperatures around 45-50 overnight. I’ve seen it done with light bulbs, but seems kind of dangerous. There are some things you can try to hold heat, such as an air tight plastic or glass cover. Compost, leaves, black containers filled with water all hold heat. If you decide to give it a try, buy an outdoor thermometer and monitor your heat overnight before you put your plants in.