March 30, 2009

Staghorn Fern Culture

Your Aunt Etta left you her mammoth staghorn fern. It took three of your friends and a pickup truck to get it to your patio. It seems that being a dutiful nephew is now requiring you to ascend to levels of horticultural science that you would rather not traverse. All is not lost. The following is a short overview of staghorn fern culture that will help you preserve both the memory of your wonderful aunt, and the fern.
Introduction
Staghorn ferns belong to the genus Platycerium and are native to tropical regions of Africa, Southeast Asia and Australia, where they grow on trees as epiphytes. There are perhaps 18 different species in the genus. The most common species grown in Southern California is P. bifurcatum, which will withstand temperatures as low as 20-22° [ degrees ] with only a lath structure for shelter. Several other species such as P. superbum, P. hillii, P. willinchii and P. stemaria are available from specialty nurseries. These species require greater protection from frost. Most of the remaining species require greenhouse cultivation.
Two Types of Leaves
Staghorn ferns produce two types of leaves or fronds. The sterile fronds are persistent, flat, and pale green, aging to tan and brown. They support the plant, enclosing the massed roots, rhizome and humus. Fertile fronds are deciduous, erect to arching or pendent and are divided into a few or many deep lobes. Due to the division, the fertile fronds resemble deer antlers. On the lower surface of the fertile fronds brown patches of spores form. The number and placement of the spore patches is distinctive for each species.
Potting or Mounting
The Staghorn ferns perform best mounted on bark, wood slabs, or slatted wood frames, furnished with moss and attached to the mount with either wire or nylon fishing line. They can also be grown on tree fern stem or, in the case of clumping species, in hanging baskets. Established plants will envelop whatever they are mounted on. All rely on atmospheric moisture rather than water directly at the roots. Daily spraying of the fronds during warm weather is beneficial with water being applied moderately to the roots. Fertilization is best applied as a monthly foliar spray on actively growing plants. Staghorn ferns grow best is bright shade or early morning sun , and will burn if given too much exposure to summer sun.
Propagation
Propagation of clumping species can be performed by division of larger offsets in the spring. The rhizome is buried beneath layers of many dead, closely packed, sterile fronds. Cut through the layers of sterile fronds until the rhizome is severed and then mount it on a fresh support. Species which do not branch can only be propagated from spores.
Pests
The most common pests of Staghorn ferns are armored scale insects. Armored scale insects live their entire adult stage attached to one spot on the host plant. They have a waxy shell-like covering that protects them from natural enemies and insecticides. If the infestation is light they can be picked off rather easily. When a valuable plant is heavily infested you can clean off all the stationary adults and then spray with broad spectrum insecticide to control the crawling juvenile stage (first test the insecticide on your fern by mixing a small amount and then applying it to a small, inconspicous area of your fern).
Common Staghorn Fern
The common Staghorn fern is P. bifurcatum. The sterile fronds are up to 24 inches wide by 18 inches long. They are papery, erect, rounded to heart- or kidney-shaped, and shallowly or irregularly lobed on the upper margin. Fertile fronds are leathery and grow up to 3 feet in length. They can be erect, spreading, or pendent, and are 2 or 3 (occasionally to 5) times dichotomously forked. Their growth habit is clumping, producing new plants as the rhizome branches. There are a number of named cultivars such as 'San Diego', which has longer fertile fronds that are darker green. Platycerium bifurcatum is native to Southeast Asia, Polynesia, and subtropical Australia.