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Acer trees (Japanese maples) are slow growing trees, though some varieties will eventually grow high and wide. As such, they’re ideal for planting in containers. But as they grow, you do need to repot an acer tree occasionally to allow enough room for its roots to spread.
If this is your first acer and your planting it on a pot for the first time, check out my guide on growing acers in pots here. If you are reporting into a new pot, carry on reading
Choosing the new pot
Acer trees like to have space for their roots to spread out. But they don’t like their roots to be deeply planted in the soil. Wide terracotta or ceramic pots are ideal for these trees. However, acers must have well-drained soil, so look for ample drainage holes in the bottom of the pot. You may need to create a few more holes yourself, and that’s not an easy task in plant containers of natural materials. Plastic containers are more suitable for this but they’re not frost proof.
I recommend that you suit the size of the container to the size of the root ball of the tree. It may be tempting to put a small tree in a large container so you don’t have to keep buying progressively larger pots. However, it’s best to increase the pot size slowly so it matches the growth of the acer tree.
Refresh the soil
You can use the repotting time to give your tree a container of new soil/compost, For red acres, I like to use ericaceous compost as it seems to bring out the reds more. But before you do this, add some pieces of broken ceramic or terracotta pieces to the bottom of the pot so that the compost/soil doesn’t wash out through all the drainage holes. Then put in a loam-based ericaceous compost. This is acidic as that’s the environment that acer trees grow best in. I also use soil based compost as it retains moisture better some look for John Innes compost.
Remove the tree from the old container
Lay the pot on its side and gently pull out the tree. Now’s the time to prune the roots before you repot the acer. Cut off the bottom of the root ball and take off some slices from the sides. Tease out the roots so that they’re laying individually and spread out, not all clumped together.
Repot the acer tree
The key to successfully repotting the acer tree is to place the root ball at the same depth as it was in the previous container. Adjust the soil in the new pot so that this is the case. Make sure that the top roots are just below the surface of the soil. Place mulch on top of the soil to keep the water from unnecessarily evaporating.
Water the tree in
Give the tree in its new container plenty of water so that all the compost/soil is moistened. Make sure that the excess water runs out of the drainage holes in the bottom of the pot.
Acers don’t suffer from many problems but they do need winter protection which I cover in this guide here. Its also good to keep an eye out for problems and catch them early to reduce the damage, I also have a guide on acer problems here