The recent publication, "Fruits of the Rain Forest," has provided a beautifully illustrated
area. Only a few of these fascinating and attractive ornamental and possibly otherwise
useful species have been introduced into California. Among the several plants bearing
colorful and interesting fruits illustrated in this publication are several fleshy fruits which
have been known to some extent for their potential value as crop plants. For example,
the Burdekin plum (Pleiogynium timorensis-Anacardiaceae) and the Johnstone River
Satinash (Syzygium erythrocalyx-Myrtaceae) and a few other species which are
presently under trial for their attractive fruits. The edibility of the fruits of most of the rain
forest species is not well known, and a few are listed as questionable or specifically
poisonous. No mention is made concerning the potential value of any of the species for
use in research and other investigations such as rootstocks for tree crop plants.
Among the Australian Lauraceae, the botanical family in which the avocado is classified,
are three major genera which could be of potential value in research programs on the
avocado. The genera Endiandra, Beilschmedia, and Cryptocarya are found in the rain
forests of northeastern Australia generally as large trees, presently only utilized for
some of their finer timber woods in the lumber trade
. Another large tree of possible
primarily for its fine wood.
Some trees of Endiandra encountered in the native bush of Queensland can be easily
and mistakenly identified as "feral" avocado. The tree itself is large, sometimes growing
up to 90 feet or more in height. The leaf of this evergreen species is very similar to that
of the ordinary avocado in size and shape and with a glossy surface. The fruit is often
large, up to 2 or 2 1/2 inches in diameter, and green in color. The fruits of some species
may develop a red, yellow, or russeted surface. At first glance and at a distance, one
might identify some of the Endiandra trees as seedling forms of the well known Nabal
avocado. A closer examination of the fruit indicates it has a comparatively thin pericarp
of fleshy tissue and a very thick stony layer of tissue surrounding the large seed.
Apparently the fruit is not eaten except by some animals, but it is not reported to be
poisonous. The large seed is reported to have been roasted and eaten by some
Aborigines. Some species such as Endiandra palmerstonii have been found to be
drought and frost tender.
Cooper's book lists 19 species of Endiandra which occur in the Queensland rain forest.
These are generally known locally as "walnuts," with an associated descriptive
character such as "brown walnut," "gully walnut," "hairy walnut," etc. Other walnuts have
such commonly associated names as Northern rose, candle, coach, ball-fruited, buff,
Noah's, rose, and Sankey's. The derivation of the use of "walnut" as a common name
for this fruit is suggested by the hard and thick endocarp tissue which surrounds the
seed and the non-edible fleshy outer portion of the fruit. The fruits of several species of
1/2 inches in diameter and spherical in form.
of the fruits are said to be edible. Nearly all of the trees of these species are tall
Some species of Beilschmedia also become large trees and bear large size fruit.
diameter. The seven species of Beilschmedia are described as large trees and with
various sized fruits none of which are said to be edible. The 12 species of Cryptocarya
are commonly known as "laurels." Some of these trees are very large, up to 70 or more
feet tall. They provide woods of excellent quality which are used in furniture and interior
finishing. The black fruits are small, ½ to ¾ inches long, and are eaten only by animals.
One species of Litsea is described as a tree reaching 80 feet. The fruits of Litsea
leefeana commonly known as "Bollywood," are inedible, small oval, and purple black,
about one inch long and seated in a cup. Still another large tree in the rain forest is
Among the other member of Lauraceae found in the rain forest is the woe-vine,
common dodders (Cuscuta spp.-Convolulaceae) which are found throughout many
parts of the world.
The above brief descriptions of some of the more prominent botanical relatives of
avocado found in the Australian rain forest are given to call attention to investigators
and others of some comparatively newly described species of Lauraceae which could
be of potential value in research programs on the avocado. Some of the materials could
prove of use as attractive ornamental specimens. The use of such species could be of
especial value in investigations on rootstocks and possibly for some of the breeding
programs in avocado research. Some reports have indicated that Endriandra has been
tried as a rootstock for avocado, but has not been successful
of Endriandra should be included in grafting or budding trials, using a wider range of
materials or repeating the trials under various conditions. An example of drawing false
conclusions from limited experiences is that noted when Persea scheideana was first
tried as a rootstock for avocado. Wilson Popenoe reported in a personal letter that the
coyo (Persea scheideana) tested as a rootstock in Honduras, "lacked compatibility' and
that "eventually the trees failed to develop satisfactorily." Later, this same species was
found to make excellent rootstock for several cultivars of avocado when tested in South
rootstock in fruit cultivars is found in the citrus group. A major and important rootstock
for cultivars of the evergreen species of sweet orange (Citrus sinensis), grapefruit (C.
paradisi), mandarins (C. reticulata) and other edible citrus selections, is the deciduous
species Poncirus trifoliata, which itself produces fruits which are generally considered
as inedible. One might not expect this combination of an evergreen species grafted on a
deciduous form to be successful or of particular advantage to the citrus grower. The
highly beneficial effects of the dwarfing effects of the trifoliate rootstock in this case is
definitely of value. Another example of graft compatibility between species apparently
widely separated in respect to botanical characters is the family Rosaceae. It is a
common practice to propagate cultivars of the evergreen loquat (Eriobotrya japnica) on
rootstocks of the deciduous species the quince (Cydonia oblonga). This combination
results in a comparatively dwarfed, yet very fruitful and valuable tree for the grower.
Thus, one should not reach conclusions on problems of grafting compatibility between
any two species of woody plants without considering trials using a wide range of
constant challenge of seeking new avocado rootstocks which exhibit disease
resistance; adaptability to adverse soil conditions such as high salinity, poor drainage;
or other soil limitations, requires that all possible botanical relatives of the avocado be
explored in respect to their budding and grafting affinity and long time compatibility.
Some of the recently described rain forest species of Lauraceae must be considered for
1. Baker, R.T. 1919. The Hardwoods of Australia,. Dept. Educ., N.S.W.
2. Cooper, W., and W.T. Cooper. 1994. Fruits of the Rain Forest. R D Press, Australia
3. Schroeder, C.A. 1990. Useful fruits of avocado relatives. Calif. Avocado. Soc.
4. Schroeder, C.A. 1987. Avocados in Australia. Calif. Avocado Soc. Yearbook 72:145-
5. Schroeder, C.A., and M. Schroeder. 1981. Some historical aspects of the avocado in
6. Fister. D. 1949. The coyo: a rootstock for the avocado. Calif. Avocado Soc.
7. Usher, G. 1974. A Dictionary of Plants Used by Man. Macmillan, N.Y.