A grove of oaks and maples gives this house in Larchmont, New York, the appealing intimacy of a woodland cottage. Although large deciduous trees take up to 100 years to grow to their mature height, a home built on an undeveloped lot can achieve a canopy effect sooner with careful siting. A rule of green thumbs: Plant each tree as far from a structure as the tree is tall. For example, an elm that is likely to reach 40 feet should be 40 feet from a house. Otherwise, spreading roots can undermine the foundation, and a falling limb may tear through the roof.