State College, Pennsylvania has managed to maintain some of its population of American elms with regular disease-monitoring programs. Part of the success can be attributed to the adequate soil space for root expansion.

Roots can grow under the sidewalks and into the lawns of the homes along this street. This has allowed them to gain tremendous size. Trees were planted about 40 to 50 feet apart in a planting strip 10 feet wide. This spacing allowed for the crowns of individual trees to touch encouraging development of a more natural upright form.

The 10' wide planting strip allowed the trunk flare to develop appropriately. Note the location of the street lights-under the canopy. This is the way to develop an urban forest.