Shallow-rooted herbaceous plants are the best variety of plant to grow in the drain field, however, some variety of trees, even though riskier, can be grown. Small, woody trees with a less-aggressive root structure are suitable. When planting the tree along the drain field, make sure it's as far away from the field as the tree's mature root spread. According to the Virginia Cooperative Extension, "one way to estimate this is by the ultimate height of the mature tree."
Weeping crabapple (Malus x scheideckeri 'Red Jade') is a variety of crabapple that grows 12 to 15 feet tall and 15 to 20 feet wide and is noted for its weeping shape and branches that come lose to touching the ground. The spring-blooming,1 1/2-inch-wide, white flower buds on weeping crabapple trees are tinged with pink to eventually open to all white. Followed are the small, bright red crabapples that mature during fall and persist into winter. The fruit on weeping crabapples are used to make jellies and are also enjoyed by birds. Weeping crabapple trees feature 3 1/2-inch-long glossy, green, tapered foliage. They grow best in full sun and moist, acidic, well-drained soil. Versatile, weeping crabapple is tolerant of a wide range of soil varieties. Plant weeping crabapple in USDA zones 4 to 8.
Flowering dogwood (Cornus florida 'Red Pygmy') is a small, slow-growing dwarf variety of dogwood tree that grows 3 to 7 feet tall and 2 to 5 feet wide, an ideal size in a drain field. It has a broad, pyramidal shape with a flat-topped habit and low branching. The early, spring-blooming flower clusters have petal-like bracts that open flat and form a large, single, 3- to 4-inch-wide flower. The 3- to 6-inch-wide oval, dark green leaves on flowering dogwood trees cast a red tinge in the fall. Flowering dogwood grows best in full sun to part shade and moist, nutrient-rich soils that are acidic. Plant in USDA zones 5 to 9.
Purple-Leaf Sand Cherry
Purple-leaf sand cherry (Prunus x cistena) is a low-growing deciduous tree that grows 7 to 14 feet tall and 7 to 10 feet wide, making it a good choice tree to grow in the drain field. It has a rounded form and single, fragrant pink blooms that are followed by the small, black fruit. The deep red to purple leaves on purple-leaf sand cherry trees are red to purple and remain in color during the summer. Purple-leaf sand cherry grows best in full sun and moist, well-drained soil. Plant in USDA zones 2 to 8.