There does appear to be a lot of dead wood on the tree. And it has been rather malpruned previously.

Dead wood should be removed as it allows for pests and diseases to make inroads to the tree and detracts from its appearance. Dead wood is usually a dull gray to almost silver color compared to the green, brown or dark red of healthy wood, and any stems or twigs emanating from it will have no visible buds.

With sharp pruners, you want to cut out all the dead wood back to where it emerges from live tissue and/or another growth point. Don't leave any stubs.

With the amount of dead showing, you may not be very happy with the appearance of this little tree once you have gotten rid of the dead. It will look pretty straggly and sparse and although it should fill in some, it may never look very good. And it is important to know how it got into this condition. JM's are not very drought tolerant and will need consistent watering attention in CA's usually dry climate. It also looks like it could be receiving a lot of reflected heat from the white walls on two sides, which could add to the tree's stress and have contributed to the die back.

So the issues to consider after pruning are a) is the tree going to be an attractive specimen in this location going forward (consider its visibility); and b) would this location be better suited to something that might be more drought and heat tolerant? Maybe you should relocate the JM to a more suitable siting and replace with something else. Something to think about.

Thank you very much gardengal48! Yes it started looking bad couple of years ago during the big drought (and CA wanted everyone to save water) but we were too busy to take care of it. It is in the front of the house so it does not look good :(

As for malpruning, it wasn't pruned at all for many years. I just pruned it weeks ago because it was too big. Only then I realized it was this bad. I don't know about pruning maple trees just tried to make it smaller.

It would be a big decision now to either do some more pruning and see how it turns out after spring, or plant a different tree. There is still chance that it is not diseased.

Do you have any links on how to properly prune maple trees? I started watching some youtube videos but I saw someone posted here saying quite some youtube videos are showing incorrect pruning techniques for Japanese maple trees.

Unless one is very skilled, it is not a good idea to prune JM's to reduce or control size, especially with weeping dissectums like this one, as it inevitably compromises or alters their natural growth habit and impacts appearance. If the tree is too big, it is in the wrong place :-)

I would urge you to consider removing it and replacing it with something that will stay in scale for the area and that will better tolerate sunlight and heat reflecting off those white walls. Transplant the maple (and now is an excellent time to do so) to a less visible, more out of the way area that receives afternoon shade and where it will be easy for you to water as needed. It is not diseased at all - just stressed from lack of water and excessive sun and heat.

You don't really need YouTube (and yes, most pruning videos are garbage) to tend to this plant. Just remove the dead wood as I indicated - back to a healthy growth point and not leaving any stubs. That is ALL the pruning that is required!

Thank you both very much. Now I learned that 1) don't prune Japanese maple trees, other than taking out dead branchs and 2) they need shady places and should by themselves keep a constant size.

Cheers.

Whoa!! Didn't mean to mislead you - like any tree, JM's do not keep to a constant size....they will continue to grow. With the weeping dissectums like yours, they don't typically grow much taller but they can get wider. It is just not highly recommended to prune to control size. And different varieties are available that grow to vastly different sizes to begin with, so you can pick the mature size you need to fit the space. There are also other reasons for pruning beyond just removing dead wood - thinning the canopy, reducing conflicted branching, enhancing form - but you don't really need to be concerned about them with this little guy.

That's fair, gardengal48, I should probably have said "roughly constant mature size and slow-growing". I have a couple of those in the backyard, but I think they are of a different kind. They grow tall and I have been thinking that they are too tall. I guess I should leave them alone then.

If you post photos of the trees when they leaf out, we can help get you close to a variety (a cultivar-specific ID is almost impossible to say with any certainty). But they do come in a huge range of sizes......30' tall to as low as 18"

nicholsworth55, nice! I think mine is of a different kind though, much lower to waist.

gardengal48, thanks for the offer. I attached two pictures here. It is cloudy today, may not easy to see. They are very tall now. You can see the fence in the back and considering there is also a slope...

I like yours too..do yours have red leaves?..mine don't have light bark..I have just one J maple with dissected leaves..the one in the front of the house in the first pic..it's growing sort of upright for that type..always looked that way..still love it..may look more like a weeper as it grows..no doubt someone early on did a bad pruning job..

bike, it is impossible to even get close without leaves :-) Give it a couple of months, then try again. And 'tall' is relative..........a great many different JM's will easily exceed the height of most fences in time. I would estimate that 12' to as much as 30' is the mature size of the vast majority of cultivars, especially in milder climates!! Even the dwarfs like 'Mikawa Yatsubusa' - which is usually listed to get only about 5-6' tall - will exceed that in time. Mine in a container is already 5' tall and only around 5 y.o.

OK, let me wait for later.