If the space under your windowsill is starting to look like the prop room from Little Shop of Horrors but it’s too cold out to put your indoor seedlings into the garden, it’s time to transfer your seedlings to larger pots. You will know it’s time because the seedlings start to get too big for their cells and/or the roots start to get “leggy” (you will see them straggling out of the bottom of the cell). If you have a garden plot ready and want to put them there instead, you will want a greenhouse-like structure to put over them for protection from frost (generally until after May 24 weekend)- this is discussed starting at step 3.
1. Fill a large container (make sure it has a hole in the bottom for drainage!) with soil, leaving a little cell-sized hole that your seedling will go into.
FOR YOU CHEAPOS: You can buy fancy soil in bags, or just dig up some soil from your garden. It will likely be far from ideal and may increase your chance of pests/problems later, but it’s free. For the container, many garden centres have free plastic ones kicking around, or you can use old ice cream, etc tubs (be sure to cut a small coin-sized hole in the bottom for drainage).
2. Very gently loosen the seedling from the cell (do not lift it out by its stem as it may break the sprout), bringing as much of the dirt with it as you can. Make sure the soil in your cell is not too dry before you do this. Place it in the hole you left in the larger container and gently press some soil in around the base.
3. The bigger containers will likely take up too much room to be kept in your home. At this point, they can go outside but will need a cold frame, which is a mini greenhouse structure that goes around them. You need to be able to prop it open somehow during the day for ventilation, but keep it closed at night to protect the plants from cold. Picture a bottomless box with a hinged glass lid.
FOR YOU CHEAPOS: After looking up “how to make a cold frame” and deciding that I am too much of a chump to accomplish such a feat, and fruitless kijiji searches to find an affordable used cold frame, I finally found the perfect solution. I bought a used 36-gallon lizard tank on kijiji for peanuts. I place it upside down over my outdoor plants. During the day, I prop it up for ventilation or remove it altogether to avoid overheating. (You have to be very careful handling it, as a reptile tank is clearly not designed for this purpose. My partner Gabe did not heed this advice and it broke. But I MacGyvered it and now it’s back and better than ever.)