SCIENTIFIC NAME: Carya illinoinensis
FAMILY: Juglandaceae

The pecan is a native of the southern United States. Although some of the large wild trees were cherished Indians and early settlers, only more recently has this tree become important, with a multi-million dollar industry in the U.S., plantings in Israel, parts of Africa, Australia and elsewhere which are expanding rapidly. The first pecans were introduced to Australia some 50 years ago, although commercial plantings are more recent.

The pecan has male and female flowers, yet frequently it is not self-fertile. This difficulty is overcome by planting complementary varieties within an area. Wind is the major pollinating agent and pollination must occur during a period of low humidity. Climatically a cool period is required to bring the tree into dormancy. During this phase, safe transplanting and shipping of young trees are possible. The trees are grown from seed, then known varieties are grafted on at 2 years or more.

From flowering in spring, the pecan requires 180-210 growing days. Trees can be difficult to remove since regrowths will occur from roots. Poisoning of stumps can affect adjacent trees since roots will frequently self-graft onto other pecan roots. The tree produces a very long tap root, which may be cut during transplantation from the nursery row, inducing lateral growths. Although the pecan needs plenty of water, water-logging is fatal. Zinc deficiency is common.

Over 180 cultivars of pecan are known, although many are no longer highly regarded. Wild trees grow to over 30m tall and bear the nuts mostly on the outer branches. Huge single trees can produce over 1000kg of nuts. However, for commercial plantings, early returns from an orchard and ease of harvesting are more important. Cultivars producing more nuts on inner branches are now favoured and planted at a maximum of 90 trees per acre. Trees are lopped at 10m and the sides are trimmed annually in rotation. Harvesting is by means of a mechanical tree shaker.

Australian growers enjoy two extra advantages: there are few insect problems affecting the pecan in this country and the Australian harvest is off-season for exports to the northern hemisphere.

Rod Shelton RFC Townsville,
(Précis by Jim Darley)

DATE: September 1981

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