I live in Ottawa, Ontario and started 2 Catalpa seeds in February. I have had to re-pot then twice as they grow quickly. They are now 28″ tall and am wondering how to overwinter them. I have no place to store them inside so have to hope Mother Nature will be kind to them until I can plant them in the spring. They will be in full sun and the soil will be loam. Believe the zone is 4 or 5.
Thank you for contacting the Toronto Master Gardeners.
We have received this question before, the following is from one of our earlier posts:
” There are a few options for your seedlings. Apparently you can plant them in the ground in the October if the seedlings are five inches high or are three to four months old. Transplant them into a permanent bed with moist soil in autumn. Catalpa trees can reach a height of seventy to hundred feet so choose a permanent site that can accommodate a tree that size. The seedlings can also be overwintered by planting each of them a sturdy plastic pot in the ground. This should be done a week or so before the expected first frost of the late fall or winter. The pot should be placed in a sheltered position. Place it in a hole that is slightly deeper than the container. Put gravel in the hole which will help with drainage in the spring. The rim of the pot should be slightly lower than the ground. Back fill around the pot and then put some soil over the top of the pot. You can put a little mulch over this but don’t let it touch the plant. In the spring as soon as the ground has thawed, lift the pot out of the ground. When fresh growth starts you can plant it in its permanent location. They can also be placed in cool space indoors where the temperatures are in upper 30’s or lower 40’s. Give the plants just a little water a few times over winter to keep the roots from getting too dry. Since you have several seedlings you can try each of the methods to find out which works the best.”
For more information please review the following websites:
https://www.thespruce.com/how-to-overwinter-container-plants-1402050
https://www.pennlive.com/gardening/2010/11/trees_in_pots_over_winter.html