Possibly shock. Was the plant rooted through the base of the container? If so this is possibly the reason.
Another possibility is some form of insect infestation (probably mites if you did not notice them).
If you scrape a small portion of the bark and the stem is still green underneath then it is fine and can be placed outdoors again in the spring.
the best dress to wear is a dress with a tree and falling leaves on it make sure as well that it is orange
They have evergreen leaves
No
physical
Lemon trees are evergreen and shouldn't lose all of its leaves. The falling of the leaves is likely due to the aging of the tree, and its leaves.
grass is a physical change.
The leaves turn shades of red,yellow, orange & brown. Then the tree slowly sheds its leaves. The leaves fall of the tree and the tree is completely bare.
The scientific name for orange leaves is Citrus sinensis.
If it does not shed it's leaves in Winter it is not an Elm.
Try some Epsom Salts this may be a Magnesium deficiency.
My aunt has a blood orange tree in her backyard. You are dripping blood on the carpet!
It depends why they are falling off. If the tree is deciduous and this happens in the Autumn then there is no problem. If it happens during the growing season it shows a tree under stress and requires further investigation.