GREEN AND GROWING

The Leyland Cypress, x Cupressocyparis leylandii, makes for a difficult screening plant. As indicated by the “x’ in its botanical name, Leyland Cypress is a hybrid, and, as is the case with many hybrids, it shows unusual vigor. In fact, under normal landscape conditions, it is the fastest growing conifer on earth, typically adding 4’ per year in height or more in its youth. The result is a 60-70’ tall tree within a few years.  Another disadvantage of this exceptional vigor is that the tree robs the surrounding soil of moisture and nutrients. The tree needs everything the soil has to offer to support its prodigious growth rate. When the tree takes all the water and nutrients, nothing is left for the adjacent lawn or other plants.

A single row of trees spaced about 4’ off center is far too close for a tree that has a natural width at maturity of 20’ or more. When the plants are so close, they usually do not receive enough sunlight on their lower branches. The result is death of the branches and with them, death of the screen. The tree can be pruned to maintain it at a smaller size, but who wants the expense and labor of annual attempts to keep a 70’ tree confined to 20’?  Amateur pruning can lead to comical results. Why not plant a tree that matures at 20’ instead?

To add to the tree’s woes, it is frequently planted where it has no chance to thrive, such as sites with poor drainage or insufficient sunlight. Combined with monoculture planting, this creates ideal conditions for minor diseases and pests to become serious.  According to Clemson University’s, Cooperative Extension Service problems with established Leyland cypress trees began emerging several years ago, and the incidence of damage from disease and insect pests has increased every year. The major problems are several varieties of fungus or mold that cause different maladies: canker, needle blight, and root rot. Bagworms and spider mites are serious insect pests. These pests can kill the trees, and because of their mature height, there is no feasible treatment once any of them infect the tree. Death will inevitably march down the entire row.

In looking at alternatives, the first rule should be to consider the plural—substitutes and alternatives.  Planting another monoculture may well lead to new problems. This is already happening with columnar arborvitae cultivars such as Emerald Green, Thuja occidentalis, ‘Smaragd’.

Good candidates include our native yaupon holly, Ilex vomitoria; wax myrtle, Myrica cerifera; narrow cultivars of Southern magnolia, Magnolia grandiflora, such as ‘Little Gem’ (also in danger of becoming over-planted) and the somewhat larger ‘Alta,’ ‘Edith Bogue,’ and ‘Teddy Bear,’ and Sweetbay magnolia, m. virginiana.

Relliable non-natives include a universe of hollies: ‘Foster’s’ holly; ‘Savannah’ holly (both cultivars of Ilex x attenuata, itself a cross between two native species); Ilex ‘Nellie R. Stevens’ and I. x aquipernyi,, ‘Carolina Sentinel’; Fragrant tea olive, Osmanthus fragrans; Fortune’s tea olive, O. x fortune;  Chindo virburnum, Viburnum awabuki  ‘Chindo’; and Camelias, both spring and fall-blooming, can make screens that are effective, manageable and beautiful.

Adventurous gardeners will explore deciduous trees shrubs and even ornamental grasses for color, diversity, and attractiveness to wildlife in a planting that doubles as a screen and a bed. Such a scheme adds depth, as well as beauty, to the somewhat boring task of merely creating privacy.