I am in Mid-Town Toronto and would love to grow a Japanese Maple in a large Japanese painted ceramic pot year round. With our climate, is that possible? Will the tree survive? Will the pot survive? Any advice you can give on whether or not this is possible would be appreciated. Of course, if it is possible and advisable, I would plant it in the Spring. Happy Holidays!
Thank you for writing to Toronto Mater Gardeners on growing a Japanese Maple in a container.
Growing a Japanese maple (Acer japonicum, or Acer palmatum) in a container is a great idea. The chance to show off your beautiful Japanese painted ceramic pot by using it as the container for an exquisite tree sounds perfect. You may wish to protect the ceramic pot by having a plastic pot inside the ceramic pot. I would suggest that you try and find a plastic container that is nearly the size of the ceramic pot, but not a tight fit. This is in case you need to lift the tree out to drain water out of the ceramic pot.
To start growing your potted Japanese maple, you will need a large container, good potting soil, and a partially sunny location for it. The first step toward having a container-grown Japanese maple is to determine a variety that would work well in your area. With hundreds of different Japanese maple cultivars available in commerce, you will need to choose one that will grow in your plant hardiness zone. Pick dwarf or semi-dwarf species for your potted Japanese maples.
Generally, these maples grow slower in pots and develop smaller root systems. If you pick a tree that doesn’t get taller than 10 feet (3 m.) tall, you won’t have to do annual pruning. If you want a healthy, happy, container-grown Japanese maple, you’ll need to plant your tree in a container that is about twice the size of the tree’s root system. It is imperative that the pot has one or more drainage holes. Keep the soil moist but not wet.
Use good quality potting soil to fill the pot. Once the tree is potted, water it well. This helps to settle the roots in the soil. Don’t fertilize until spring, and even then dilute a water-based fertilizer to half-strength. If over time, you see that the roots of the Japanese maple in a pot touch the side or bottom of the container, it’s time for root pruning. Clip out the big, wood roots. This lets smaller roots develop.
Japanese maples grown in pots in the coldest recommended growing zone may need protection in winter by moving them into an unheated garage or shed. Plants in containers do not have the root protection that plants in the ground have so they are not as cold hardy. For example, if your tree is recommended for zones 5 to 9 it is more like 6 to 9 when growing outdoors in a pot.
Repot your Japanese maple into a larger container when the tree is starting to become root-bound in the pot. To determine if your tree needs to be repotted check for these signs:
- Roots coming to the soil surface
- Roots coming out of the drainage holes
- The soil no longer retains water. As the roots take over there is less and less soil to help hold onto water.
Here also is a Toronto Master Gardener article that may be helpful. https://www.torontomastergardeners.ca/askagardener/growing-a-japanese-maple-in-a-container/
We wish you every success in planting a Japanese maple.
Wishing you happy holidays as well.