Leyland Cypress (Cupressocyparis leylandii) is a popular landscape ornamental across the southeastern United States. This rapid-growing evergreen typically reaches 70 feet high--and often exceeds 100 feet. This is a densely branching, pyramidal tree with feathery, flat, dark-green or blue-green foliage, note Clemson Cooperative Extension specialist Debbie Shaughnessy and horticulturist Bob Polemski. Leyland cypress demands a large space, especially when fertilizer use stimulates its growth rate even more.
Its naturally rapid growth rate has led to a broad spectrum of fertilizer recommendations. Authors Felder Rushing and Jennifer Green of the "Alabama & Mississippi Gardeners Guide" caution that more than a light feeding "every year or so" produces a weak tree. "The New England Gardeners Guide," on the other hand, advises semi-annual spring and fall feedings with a slow-release fertilizer, guaranteeing the tree a steady supply of nutrients.
Commercially Grown Trees
Leyland cypresses and other conifers that are grown for the Christmas tree market efficiently absorb soil nutrients. The University of Georgia's associate professor Orville M. Lindstrom and colleagues suggest that the types of fertilizers commercially grown Leyland cypresses need depend on their ages and growing conditions.
New Cuttings and Fertilizer
Leyland cypresses commercially grown for Christmas trees are propagated from branch cuttings grown in a porous growing medium. A 1:1 mix of perlite and peat moss is typical. When the cuttings develop roots, they benefit from weekly doses of diluted 20-20-20 liquid fertilizer. The fertilizer's numbers indicate its percentages of nitrogen (N), phosphate (P) and potassium (K). The fertilized cuttings are usually ready for larger containers in three months.
Rooted Cuttings and Fertilizer
Transplanted to 1-gallon containers of a sand and ground pine bark medium, the cypress cuttings benefit from 2 tsp. of granular, slow-release 18-6-12 formula fertilizer mixed into each pot. This amount sustains them for the six to nine months they need to grow large enough for outdoor planting.
Planted Cypress Fertilizer
Commercial growers always run autumn soil tests before planting out rooted Leyland cypress cuttings in the late winter or spring. The results determine which types of fertilizers, in what amounts, the soil needs. A fall application provides time for them to break down before planting. Leyland cypresses perform best at soil pH levels between 5.5 and 6.0, with potassium levels and phosphorous levels of 100 and 50 lbs. per acre, respectively.
In properly prepared soil, the trees need 1 tbsp. of slow-release, 18-6-10 fertilizer formulated to release nutrients over three or four months. Trees should receive the fertilizer in two separate feedings, the first in March and the second at the end of June or in early July. The fertilizer should also contain essential nutrients such as manganese, copper, magnesium, iron, boron and zinc.