r? We were unable to plant it for three weeks after it was delivered in October by which time a lot of the leaves had fallen off.
Leaves will start out small, and grow larger. Likely, it needs more time.
However, if the tree stays stuck throughout the year, then I would suspect that the roots were disturbed too much during transplant. It will take some time to recover, but as long as you care for it as it should be, then it should recover just fine.
Here is an article that will help you with its care:
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm
Our neighborhood has 40+ Katsura trees lining our alley. They have grown tall over the last 15 years and now are creating lots of damage on the fences and rooflines that end up being under the canopy (especially during summer and fall). It seems that the trees drop a lot of "stickiness" on everything and anything that lies temporarily or permanently under them. Cars have even been damaged from the "sticky sap". Do these Katsura trees typically do this after mature, or is it that they are potentially unhealthy or diseased?
This can be normal with high variability in temperature and humidity. This can be a sign of insect pest infestation, though, as well as bacterial infections.
Unfortunately, your photos did not come through. I will be unable to assess the situation, further.
These articles can help:
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/wetwood-bleeding-trees.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/aphids-tree-disease.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/control-plant-scale.htm
If the tree isn't fed on occasion, then this could be the issue. They do enjoy feeding, and will take up nutrients quite quickly!
This article will offer more information on the care of these trees:
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm
We moved into a house with a Katsura tree. Over the past 3 years we are noticing that it sheds its leaves very early each year. (They are falling now, in August.) Is this normal?
It is not normal because the leaves are supposed to turn colors in the fall before dropping. The trees are cold sensitive, but I'm sure you are not having cold weather in August. However, after doing some research, others with Katsura trees report early leaf loss due to hot weather or drought. They are not drought tolerant and prefer a moist soil, so if the area around your tree is dry, that likely accounts for the early leaf loss. Trees will drop their leaves in order to save themselves if they encounter stress.
So, if you are experiencing any of those environmental issues, you can chalk it up to that, but if not, I would check the leaves for evidence of disease, such as spots, or insect pests such as scale or aphids.
https://trees.umn.edu/katsura-cercidiphyllum-japonicum
https://www.gardeningknowhow.com/ornamental/trees/katsura/japanese-katsura-tree-care.htm