I have a self seeded Japanese Maple, about two feet tall. It is growing into another self seeded Japanese Maple which is much larger, approx 3-4’ tall. I would like to separate the smaller one from the larger one, and pot into a container. I would like to keep the tree in the container permanently. When would be the best time to attempt this? And advice on containers? Any advice at all, is appreciated. I am in south Etobicoke. Many thanks.
Thank you for contacting the Toronto Master Gardeners. How lucky you are to have two Japanese maple seedlings ! Japanese maples (Acer palmatum) are lovely in containers. The best time to transplant your smaller seedling to a container is the fall. At this time, the tree can direct its carbohydrate stores to root growth, which continues in the fall and early winter when the temperatures are above freezing. The second best time for this transplant is the early spring, but you need to careful not to damage new growth.
It’s best to put your seedling in a pot that is about double the size of its rootball. Japanese maples grow best in a somewhat snug pot, and too much soil around its roots could result in too much moisture which could lead to root rot. So you will likely need a series of pots as your tree grows to its final size. It is most important that the container have drainage holes. Japanese maples like a lot of water, but it must drain away so that it does not cause root rot.
In a container, roots will freeze more quickly than in the ground. The biggest challenge for any plant in a container that is outdoors year round is the freeze / thaw cycles that are part of our winters. Your container will need to be able to withstand this (so no clay or ceramic), and you will need to have an overwintering plan for your Japanese maple. Depending on its size, this could mean moving the pot to a sheltered location out of sunlight and the wind in an unheated garage or corner of the garden, adding lots of mulch (3-4 inches) on top of the soil, and insulating the pot by covering it with straw or bales of hay. The goal with insulation is to maintain an even temperature. Your Japanese maple will also need to be kept well watered through several heavy frosts until it is completely dormant.
The Toronto Master Gardeners have a couple of Garden Guides that might be helpful :
Growing Japanese Maples: A Toronto Master Gardeners Guide
Container Gardening: A Toronto Master Gardeners Guide
The Toronto Master Gardeners have answered lots of questions about Japanese maples. You can see these questions and our responses by typing Japanese maples in the Search box that is below Find it Here on our website Here is one response that you might find helpful :
Growing a Japanese Maple in a Container
Good luck with transplanting and growing your Japanese maple seedling !