Just some clarification, please. Have these been in the same container for all that period of time? Have they ever been repotted or root pruned? Have you ever provided any fertilizer during this period?

If the answers to these are yes, no and no, then I am a bit surprised these trees are even hanging on to life as tenuously as they may be. While it is perfectly possible to grow these trees in containers long-term - even permanently - they will require regular attention to keep them thriving. This would include repotting and root pruning at least every 5 years (possibly more often if in smaller pots) while at the same time refreshing the potting medium. Left too long without this attention, the roots will fill the container and become choked. They will also take up all the space, with the potting soil virtually disappearing over time. When this happens, it is almost impossible to keep the root mass properly hydrated, even more so in a windy climate, and even daily deep soakings may not be enough in summer. And the need for frequent watering of any container-grown plant leaches the soil of any nutrients. These must be replaced on a regular basis so fertilizing is always necessary. How often depends on how frequently you repot and what type of fertilizer you use. A slow release fert at the time of repotting and again each spring as the trees leaf out will get them off to a good start, but I'd recommend supplementing with a dilute liquid fertilizer weekly throughout the growing season as well.

When you water, water the container soil only. It is of no benefit to the tree to water the trunk or foliage and Japanese maple foliage is quite delicate and can be damaged with watering in strong sunlight. Water slowly until the water runs freely out the bottom of the container. If this happens very rapidly, you can bet your trees are very rootbound and need attention ASAP.

Wow, thanks, that is very helpful information. I admit, due to other issues in my life, I have totally neglected them. I do have a question, however: Can I replant into the same pots? They are about 1/2 barrel. If so, can I trim the rootball? Thanks so much for your time, Marilyn

Yes, half barrel containers are large enough to support most Japanese maples long-term, provided you give them necessary care. Growers often supply relatively large trees to nurseries in 24" boxes and I have one growing in a barrel container myself.

You'll need help to do it, but gently lay the tree in the container on its side (or as close as you can get without damaging it) and slide the rootball out. Loosen it and the soil as best you can - I like to use a hose and wash the soil and this seems to loosen the roots as well. Then with a clean pair of pruning shears (sterilizing them won't hurt and is worth the effort) remove any roots that look dark or discolored and about 25% of the outside roots. Try to avoid anything of major size - just remove the finer stuff. Repot in fresh, good quality potting soil - something with a lot of bark fines - add some slow release fertilizer like Osmocote and water well.

Ideally, this should be done while the tree is still dormant, as this will result in the least amount of shock to its system, but I have done it at various other times of the year as well.

What you see happening is very normal for ornamental japanese maples (grafted trees). Each August is when many times they lose their set of leaves from that spring and the plant hardens off (that is when my wife does her summer grafting, when the japanese maples harden off in august then you will probably notice a nice new set of leaves begin to come out and then get the nice fall color of whatever variety you have and then the tree will get ready for winter and harden off again in later november/december...

Like you I was wondering what was going on with the trees a few summers back and my wife has explained a lot to me as she and her family had a little japanese maple nursery...

Enjoy you time,

Keith

I would have to say it is NOT normal :-)) And especially for trees being grown in a container long term without attention. Japanese maples do not customarily lose all or even most of their leaves in summer - when they do it is a sign they are under a great deal of stress. What they can do (and this is by no means uniform for all cultivars) is put out a summer flush of foliage but in doing so, they do not drop the existing leaves.