LEAD: Sometimes homeowners go through the prudent steps of obtaining three or four bids for pruning or cutting large trees and find that one estimate is significantly lower than the others. It would seem sensible to accept the low bid, the National Arborist Association says, but only if the tree contractor can show proof of liability insurance.
Insurers rank tree workers among the high risk trades when it comes to writing liability policies. The reason is the danger of damaging property in the process of tree pruning or cutting, as well as negligence that can cause propoerty damage, injuries or later, death as a result of injury. Improper pruning can weaken, imbalance and fell a tree.
A low bid can be a tipoff that the contractor lacks liability insurance. The cost of liability insurance, as well as workers' compensation insurance, adds to overhead costs for tree contractors. The costs are passed to customers and reflected in bidding. Homeowners should also be wary of contractors who accept only cash payments, and they should get a written estimate that details the work, including cleaning up and disposing of debris.
Also important in selecting a contractor, say arborists, which is what trained and experienced tree workers prefer to call themselves, is the quality of the finished product. Asking for references from homeowners who have attractive yards and trees is the best way to get a measure of an arborist's work.
A few states - Connecticut, Massachusetts, and MARYLAND - require arborists to be licensed. In effect, the person who makes the recommendations, prepares the estimate and oversees the work as it is being done, has the license.
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