A plant's root system is the most important organ for its nutritional needs and growth. Because each plant has a different size, depth and character of root, the location, feeding and watering should be tailored to the plant's needs. Leyland cypress are usually grown as a privacy hedge and have an extremely fast growth pattern. The trees can get extremely tall very fast,so careful shearing and reduction of the height is important to help the undefined root system stabilize and feed the tree.
The Leyland cypress is grown as an ornamental hedge. It can average 3 to 4 feet per year and is a heavy feeder. They are popular Christmas trees in the South probably due to their fast growth. The trees are resistant to most pests and diseases and a good central leader that stays straight. Leyland cypress are actually a false cypress and not related to true cypress. They are evergreen and all are sterile hybrids. The tree does not occur naturally and must be propagated by root cuttings. The maintenance on the Leylands is something to think about if considering planting, as it will need shearing at least twice yearly.
The Root System
The Leyland cypress has a fairly poor root system. It does not have a main taproot, which can make it very unstable in bad weather. The roots are small and very shallow, staying close to the surface of the soil. Additionally, the spread of the roots is minimal, especially for such a large tree. The roots will be at the top 2 feet of the soil where the most nutrients and water are held. On clay soils the roots may be even shallower, around a foot. The root spread is relatively small will depend on the size of the tree. For a 67-foot tree, main roots only spread about 30 feet outward.
Due to the shallow root structure, the Leyland cypress is vulnerable to high winds. Tipping over or becoming tilted is common since they don't have much of a grip and are rather top heavy. Overly wet soils can loosen the plants roots. Additionally, planting too near a driveway or paved path can impede root growth. The roots are fairly close to the surface and can fall victim to lawnmowers. The plant can also fall prey to other hardier root systems that are in competition for space and nutrients.
Two main diseases plague the Leyland cypress. Phytophthora rot is a disease that affects smaller roots and smaller trees. It causes yellowing of the foliage and tip die back. The disease is worse in areas with poor drainage and can only be diagnosed by a lab. The other disease is Annosus root rot. It starts with a fungus that grows on plant stumps, primarily pine. The disease travels through the roots of the stump and is spread by touching other plants roots. The large roots of the newly infected tree die and eventually the tree will die. The symptoms start with yellowing of the roots and can progress to brown or reddish brown foliage. The fungus may actually appear on the base of the affected tree and grow small irregular brown and white fruiting bodies. There is no cure for this disease.
It is useful to remember "right plant, right place" when considering a new addition to the garden. In the Leyland's case, it is good to remember it needs full sun, well-draining soil, no large competing neighbors and regular pruning. The relatively undeveloped root system will sustain the plant quite well since it is a hardy species, as long as it has regular maintenance and care. To avoid the root disease Annosus, always remove the stump of any tree or treat it with granulated Borax.