- How long can I keep Japanese maples in pots?
With proper care, Japanese maples can live a long and healthy life in a pot. Choose a smaller or dwarf variety of maple, although container culture is a natural dwarfing process so the tree will never grow as large in a container as it would in the ground.
Consider the eventual location of the pot as part sun or shade. Maples will not tolerate full sun. Also variegated varieties tend to lose their leaf colour and become greener in the sun.
Choose a good size ceramic or terracotta container at least 2 to 3 times the size of the root ball with good drainage holes. If you leave the maple too long in too small a container, you will develop root issues that will dramatically shorten the life of the tree.
Use a light loam-based potting soil with a high level of organic matter to facilitate drainage. Never use a soil direct from your garden and never use a soil with added fertilizers. Through the years it may be necessary to reinvigorate the soil with specific mineral additives such as an iron-based product.
Minimal fertilization is required. If leaf colour is diminished, use a slow-release fertilizer formulated for acid-loving plants once a year in mid-March to allow time for the maple to go dormant before the winter weather arrives.
Water deeply once a week in the morning until you can see water drip from the drainage holes and avoid water touching the leaves. As our summers are getting hotter and drier, a container maple may need watering twice a week while a top dressing of three to four inches of mulch helps keep in the moisture during such hot dry periods.
Water sparingly over the winter to keep the pot slightly moist.
In general, maples require little overhead pruning. If needed, prune during the dormant season during a dry spell cutting out any dead, diseased, or damaged branches, then prune to shape.
If you are finding that water does not soak through the pot or the leaves become crispy and unhealthy looking, it may be that the maple has become root bound over the years. Root prune in February right before the weather warms up and use fresh potting soil and sterilized tools. Even in a suitably large container, root pruning will be required in about 3-5 years to keep the tree in proper health. Consult a nursery before attempting your first root prune.
Sources:
Gardenia “Great Japanese Maples for Containers”
https://www.gardenia.net/guide/great-japanese-maples-for-containers
Russell Nursery “Repotting Large Containers” (local nursery located in North Saanich)
https://russellnursery.com/articles/repotting-large-containers
Garden Gate Magazine “How to Root Prune Container Grown Trees”
https://www.gardengatemagazine.com/articles/how-to/prune/root-pruning-container-grown-trees
Royal Horticultural Society UK “Trees Growing in Containers”
https://www.rhs.org.uk/plants/types/trees/container-growing