Sharon, Thanks for the question. The tree is stressed. The cause could be one or more of many things. Drought conditions over the past couple of years. Trees have a delayed response to drought. It could have been planted too deep, which causes stem girdling roots. There could be trunk damage from a lawn mower or weed wacker. Less likely, but there could be root damage from construction. Linden trees are not tolerant of road salt. Lindens are a favorite of Japanese beetles, so if the tree is severely defoliated several years this could cause decline. Not likely squirrel caused.

Remedy: make certain that the tree gets additional water during dry periods. Slow deep soaking weekly.

Good luck. Trees want to live so with extra care it should recover.

Paul

Tree Care Advisor volunteer