We all know what a mule is. It’s a cross between a female horse (Equus caballus) and a male donkey (Equus asinus). Since the parents are different species the mule is sterile.
Leyland cypress is a lot like that, except its parents are even more distantly related. Leyland cypress is a cross between a Monterey cypress (Cupressus macrocarpa) and a Nootka false cypress (Chamaecyparis nootkatensis). These two trees are not only different species, but they’re also of different genera.
So, what does that all really mean? For one thing, this plant could never become invasive, because it doesn’t produce viable seeds. That’s one of its good points. Unfortunately, it probably has more bad traits than good ones.
Leyland cypress is fast growing. That can be good if the desired effect is developing a screen in a hurry. Many people use this plant as a windbreak because it grows quickly. Unfortunately, like most fast-growing species it has a shallow root system and plants often blow over.
Another problem is that most people look at Leyland cypresses as large shrubs and plant them too close together. These things can get over 60 feet tall. When planted close together they grow spindly and are even more subject to toppling over.
It’s easy to see why landscapers and homeowners like them. They have attractive bluish-green color, and they grow quickly. Even small specimens can make an impact in a short time. They also are used a lot in coastal areas, since they’re quite resistant to salt spray.
Leylands thrive in a wide variety of soils but won’t tolerate extremely dry or extremely wet environments for very long. Here in the southeast, those conditions can be common and last several weeks. When plants become stressed, they are susceptible to diseases and insects.
Bagworms are a major problem around here. If I need to find samples for teaching purposes, I can always find some. Older trees in dense plantings seem to be the most susceptible. Once bagworms become established it’s only a matter of time before all trees in the planting are affected and ruined. Spider mites can be problematic, too.
I like the idea of using these trees as a screen, but I would consider them a short-term screen. I’d plant a slower-growing, deeper-rooted and more disease and insect resistant species between them with the idea of removing the Leylands in a few years. That way I’d have privacy over a longer period.
In recent years, Leyland cypresses have become popular as Christmas trees. They respond well to frequent pruning and can be shaped quite easily. Branches don’t have the strength of firs, spruces or scots pine, and they don’t have traditional needles, but the crop can be marketable at a younger age.
My attitude toward this species is far less negative as it is toward the ornamental pears. They are a true scourge of the earth. I think Leyland cypress has some fine qualities. It’s not invasive, but it’s overused. We need to be more imaginative. There are many more evergreens at our disposal.
Ted Manzer teaches agriculture at Northeastern High School.