In the heat of the summer, measure the temperature under the shade
of a mature tree.
Using the same thermometer, measure the temperature in a shadeless
area.
The difference will be about ten degrees.
A tree to shade your house could save you money
on your energy bill.
Find out how long the company has been in business.
Ask if they follow the standards recommended by the International
Society of Arboriculture Tree Pruning Guidelines, ANSI A300
Pruning Standards, and ANSI Z133 Safety Requirements.
Ask for verification of appropriate professional certification
such as by the International Society of Arboriculture for arborists.
Ask for certificates of insurance, including proof of liability
for person and property damage, and workman's compensation.
Ask for proof of state contractor's license.
Ask for at least three local references.
Have more than one professional look at the job and give estimates.