Durham keeps its trees. Along the Coginchaug and up the traprock east of town the canopy closes over the road by June and holds the heat off the fields below. Connecticut Tree preservation works inside that canopy — pruning limbs and hangers gone dead or dangerous, taking down what cannot be saved, and meeting the pests that arrive on schedule every year: winter moth, gypsy moth and tent caterpillar in the leaves, hemlock woolly adelgid, mites and aphids on the evergreens and ornamentals. Their work runs downward too, into liquid fertilization for root systems lacking nourishment, tree injections against pine borer, soil rejuvenation with custom-blended nutrients, and organic tick control across the ground where the family and the dog actually walk. A hemlock carried another decade is worth more than anything you could plant to replace it, and that arithmetic is the whole idea sitting right there in the name. Come August, when the shade over Durham is deep and unbothered, you can see what all of it was for.