Plant Health Alert – Leyland Cypress

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sick Leyland cypress

Leyland cypress trees are often planted too close together. This leads to depletion of soil nutrients and water, competition for light, insect infestations and fungal diseases.

When Leyland Cypress trees were first promoted by the nursery industry the plants were thought to be pest resistant. Unfortunately after hundreds of millions of these trees have been produced and planted in landscapes we have learned that Leyland cypress trees are prone to a number of diseases that tend to infest them and sometimes kill them. The plants start to fall apart just when the trees are at their most beautiful 10-20 years after planting.

Leyland cypress plants grow quickly making them popular as hedge plants. They grow so fast in fact that they can rapidly outgrow their soil space and use up soil nutrients. More often than not Leyland cypresses are planted too close together and have outgrown their space. The ultimate height and width of a Leyland Cypress is 150’x60′! If you plant them 10′ apart then they are bound to outgrow their allotted space.

Browning Needles

leyland cypress needle drop

Make sure Leyland cypress get plenty of sun, water and fertilizer.

Many calls we get are about browning needles in Leyland cypress. Browning needles in the interior of conifers is a natural part of the plant getting larger and older. Conifers such as pine, cypress, cedar and arborvitae start out as young Christmas tree shaped plants. These young evergreen trees have limbs all the way to the ground and needles extending into the interior of the plant. As the plant gets larger, upper limbs begin to shade lower limbs. The interior of the plant gets shady. Since the only reason for a needle to exist is to gather sunlight, the plant stops supplying the needles in the shade with nutrients and the needles turn brown.

Browning needles can also be caused by a plants tendency to favor new growth over old growth. A plant will take nutrients from older less productive leaves and move the nutrients to the outer newer more productive needles. If the plants get dry, they will favor the outer needles over the inner needles. 
Due to the stress Leyland cypresses that are planted too close together trees undergo they are susceptible to fungal diseases. Several fungi can cause dead needles and limbs.
leyland cypress get very tall
Suggestions to maintain Leyland cypress trees:
  • During the winter months, prune out the dead branches.
  • Remove trees that are mostly or totally dead.
  • Hedge back the longer limbs that are touching other trees.
  • During the growing season, fertilize the trees with 10-10-10 at 1 lbs per tree once in May and once in August. 
  • Irrigate the trees during periods of drought.
Spraying Leyland cypress to prevent disease will not be as beneficial as taking care of the trees properly. If you have an older overgrown hedge of Leyland cypress you should make sure the plants get plenty of sun, water and fertilizer.
If you need further direction or would prefer to hire a professional to care for your trees, you can hire a tree care company.

Written By

Steve Pettis, N.C. Cooperative ExtensionSteve Pettis, Jr.Extension Agent, Agriculture - Consumer and Commercial Horticulture Call Steve Email Steve N.C. Cooperative Extension, Henderson County Center
Updated on May 2, 2023
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