ichidan verb
die at the top; wither from the top down
Used of plants, especially trees, when the upper part dies or withers first. Rare and somewhat literary; in everyday speech, 上が枯れる or 先端が枯れる are more common.
その松は上枯れている。
That pine tree is dying from the top.
日照りで庭木がうわがれてしまった。
The garden trees withered from the top down due to the drought.
General verb for plants withering or dying; 上枯れる specifies that the top part dies first.
Compound of 上 (うわ, 'upper part') and 枯れる (かれる, 'to wither'). The exact historical derivation is uncertain, but the meaning is transparent from its components.