That tree in your yard you value so highly - if something happens to it, are you prepared to prove a casualty loss? Or for your lawn?

A thick, green weed-free lawn will add an average of more than $1,400 to the resale value o a $45,000-50,000 house, accordidng to a recent survey of realtors in Chicago, Denver and Northern New Jersey.

Attractive flowers, trees and shrubs around the home will add about $1,500 to its value, the survey indicated.

Almost everyone knows that trees and other growing plants have value, says the American Society of Consulting Arborists (ASCA), Washington, D.C. What many don't realize, however, is that their value can be expressed in dollars and cents, both in increasing the worth of the property on which they grow and in recapturing the casualty loss if they are damaged.

In most cases, a casualty loss is defined as one resulting from an identifiable event of sudden, unexpected or unusual nature. It may be due to natural causes - wind or ice storms, lightning, or floods, or it may be an accidental loss, such as damage from an automobile colliding with the trees and other landscape plants are used in planting designs from a functional and objective viewpoint, they can be evaluated as an entity separate from buildings or property as a whole, according to ASCA specialists.

Making this evaluation is the work of qualified professional arborists and nursery men, they say. Their guidelines are widely recognized and accepted by insurance companies, the courts and under certain conditions by the Internal Revenue Service - the three major avenues of compensation for casualty losses.

Here are some things property owners can do to help them benefit from all this, ASCA specialists say:

First, and most obvious, protect and care for the trees and other landscape plants on your property. They are valuable.

Take pictures of the trees now, while they are alive, well and happy. In case damage is claimed as a tax decuction, the Internal Revenue Service asks for "before and after" photos.

The shade your trees provides on your house, patio or other living area is worth money you can claim as part of a casualty loss. A farmer in Tennessee was allowed a business loss by IRS when his cattle were deprived of the benefit of the shade from trees destroyed in his pasture.

Find out if insurance regulations in your state allow an increase in the amount of claim permitted from loss of trees. In some states that amount has been raised from $250 to $500 per tree.