Etymology: not known, but the name was given to the Series
Alveolatae by JH Maiden in his Critical Revision of the Genus Eucalyptus (1929); Brooker has elevated that series to the status of subgenus. There is only one species, which is common in the Eastern Highlands of Zimbabwe, but is known to have been planted (and failed) only at the Forest Research Centre in Harare. This species was planted quite commonly at one time, and it is possible that there are some specimens within the city limits (see Appendix 1).
Etymology: from the Latin cuboideus, alluding to the shape of the seeds. This subgenus was formerly included in Gaubaea by Pryor and Johnson. The single species has not been introduced into Zimbabwe.
Etymology: from the Greek idiogenes (peculiar, unusual), in reference to the distinctive features of the only species.
It is a plantation tree of major economic importance in the warmer parts of the Eastern Highlands, but the only known planting in Harare was at the Forest Research Centre, where it failed (see Appendix 1).
Etymology: from the Latin primitivus (primitive), alluding to the developmentally primitive nature of the single species
compared with the advanced sister subgenus, Eucalyptus. The species is a relatively recent discovery, and has not been introduced into Zimbabwe.
Etymology: from the Greek eu (well), and kalyptos (covered), in reference to the operculum, which covers the reproductive parts of the flower. All species have only one (calycine) operculum, which is shed at flowering. There seems to be no evidence of even a vestigial corolla. This subgenus, which was formerly named Monocalyptus by Pryor and Johnson, is the second largest in the whole genus, and comprises 11 sections, 3 subsections, 24 series, 10 subseries, and 110 species. The subgenus Eucalyptus is economically the most important in Australia, containing some of the most extensive forests, with the largest trees, and the best-quality timbers. But this group has provided few really successful introductions into other parts of the world. Some species, like E. marginata (jarrah), are simply not adaptable outside of Western Austr- alia, and many others perform inconsistently as exotics. It seems that the species of subgenus Eucalyptus suffer nutrit-ional disorders in exotic environments, possibly associated with the absence of suitable mycorrhizal fungi, but this has not yet been proven experimentally. A total of 37 species of this subgenus have been introduced into Zimbabwe, and about six of these have done well in some experimental plots, but not in others. Perhaps the most notable successes have been
E. regnans (mountain ash) and E. pilularis (blackbutt), but they have not done consistently well. Only seven species of subgenus Eucalyptus are known to have been planted in Harare,
but none of these has survived, although there is no climatic reason why some of them should not have been successful.
COMMON NAMES OF THE EUCALYPTS
The common names of the eucalypts in Australia probably run into thousands, since any one species may have several common names, especially if it has a wide natural distribution. As a whole group the eucalypts are known as gums, but the name gum is usually reserved for those species that have a smooth bark, because some of them tend to exude a dark reddish kino (wrongly called gum) from injuries to the bark. Some other common names are:
bloodwood - timber often has pockets of kino;
stringybark - bark is very fibrous and can be pulled off in long strings;
blackbutt - rougher bark on lower part of bole usually charred by fire;
ash - pale-coloured and easily split wood reminded early loggers of the wood of European ash (Fraxinus excelsior);
box - wood bears a superficial resemblance to European box, (Buxus sempervirens);
peppermint - leaves contain oil that smells like peppermint;
ironbark - bark is dark coloured, deeply furrowed, and extremely hard;
red gum - has a reddish timber;
blue gum - has bluish-coloured bark or juvenile leaves;
tallowwood - wood has a greasy feel;
karri, coolibah, etc - Aboriginal names.
In southern Africa the widespread use of the name blue gum (or bluegum) for all eucalypts probably dates back to the first introduction of eucalypts into South Africa in 1828. The species was E. globulus, and it came in under the common name blue gum, although in Australia it is better known as Tasmanian blue gum or southern blue gum. By the turn of the century this species was being widely planted in the Cape Province and Natal, and the name blue gum must have been firmly fixed. Another blue gum was introduced into South Africa towards the end of the last century, which would have further entrenched the use of the common name: this was the Sydney blue gum, E. saligna. In actual fact the seed that had been imported was a mixture of Sydney blue gum and flooded gum, E. grandis, mostly the latter, but at that time Australian botanists did not recognize E. grandis as a distinct species.
E. grandis was introduced into Zimbabwe as E. saligna in 1892, and the common name blue gum came with it. Although condit- ions here are very suitable for true E. saligna, little has been planted in the country other than in research trials. The other blue gum, E. globulus, has not done well in our summer-rainfall climate, and hardly any of it has survived outside of the Nyanga National Park. The name blue gum, therefore, has practically no validity in Zimbabwe, but it is widely and indiscriminately used for any eucalypt.
In the species descriptions that follow technical terms will be kept to a minimum, but it will not be possible to avoid them altogether. Terms that will appear in the notes are listed and explained below:
alternate (leaves) - leaves scattered on the stem, not opposite
amplexicaul - stem-clasping; base of leaf embracing stem
anther - pollen-bearing organ at tip of stamen
apiculate - ending abruptly in a short point
ascending - when the disc is convex or raised between the staminophore and the valves
axillary (inflorescence) - borne in the upper angle between leaf and stem
beaked - the operculum is contracted to form a beak
bole - the trunk or stem of a tree
calyx (adj. calycine) - outer whorl of floral "leaves", composed of free or united sepals
capsule - dry, dehiscent, seed vessel; in eucalypts this is partially or wholly submerged in the hypanthium
compound (inflorescence) - the inflorescence is branched, and not simple (qv)
concolorous - when leaves are the same colour on both sides
cordate - heart-shaped; particularly the indented base of a leaf
corolla - inner whorl of floral "leaves", composed of free or united petals
corymb (adj. corymbose) - inflorescence in which the lower flowers have longer pedicels than the upper ones, thus tending to bring them all to the same level
crenulate - scalloped or toothed with small rounded notches on the margin of a leaf
crown - the leafy head of a tree
decorticating - shedding of bark from a tree
dehiscent - splitting or rupturing at maturity, usually referring to the spontanbeous opening of seed capsules when ripe
deltoid - triangular, or D-shaped
descending - when the disc slopes downwards towards the valves
disc - band or ring of tissue between the ovary and the base of the stamens
discolorous - when the leaf surfaces differ in colour
endemic (of plants) - confined to a particular region
falcate - curved like the blade of a sickle
family - a group of allied genera
fibrous - when the bark is non-decorticating and is held in short or long fibres, usually dense, but often held loosely on old branches, or towards the base of the trunk
fruit - in a eucalypt a composite structure of the seed- bearing capsule held within a woody hypanthium, opening at the top where the seeds are shed after dehiscence
genus (plur. genera) - a unit of classification in living organisms, comprising one or many related species
glaucous - covered with an ashy or greyish bloom
gland - in eucalypts small or minute oil-containing structures seen in the leaves and other parts of the plant
globose (of the fruit) - somewhat globular in form
hypanthium (plur. -ia) - in eucalypts the broadened invaginated structure at the top of the pedicel, partly or wholly enclos- ing the ovary
inflorescence - the flower-bearing portion of a plant, includ- ing the flowers themselves; the arrangement of flowers on an axis; may be simple or compound
intramarginal vein - the vein running more or less parallel to the edge of a leaf
kino - a dark reddish exudate that often impregnates the dead bark; incorrectly called gum
lanceolate (of leaves) - lance-shaped; broader towards the base and tapering to a point
lignotuber - a woody structure developed from swellings assoc- iated with leaf nodes at the base of a plant; common in eucalypts, becoming massive in mature trees and mallees
mallee - a type of eucalypt in which several stems arise from an underground lignotuber
obconical - conical but inverted, with the narrow end to the point of attachment
oblique (of leaves) - when the two sides of the leaf base meet at different points on the midrib or petiole
operculum - the cap of a flower bud formed by the fusion of sepals or petals, and covering the stamens; it is shed at maturity to expose the reproductive organs
ovate (of leaves) - egg-shaped, with the broadest part towards the petiole
ovoid - egg-shaped (of solids)
panicle - a branched inflorescence
pedicel (adj. pedicellate) - the stalk of an individual bud, flower, or fruit
peduncle (adj. pedunculate) - the common stalk of a cluster of flower buds, flowers, or fruits
peltate - when the petiole of a leaf is attached on the underside within the margin
petiole (adj. petiolate) - the stalk of a leaf
reticulation - network of veins in a leaf
rim (of eucalypt fruits) - the upper edge of the mature fruit
scar (on buds) - the narrow band left on the bud by the shedding of the outer operculum
sessile - of a leaf, bud, or fruit lacking a stalk
simple (of inflorescence) - when it is unbranched
species - the basic unit of classification, which usually refers to one or several groups of plants (or other living organisms) that interbreed and maintain their distinctive identity through successive generations
stamen - the pollen-bearing organ of a flower, comprising a filament surmounted by an anther
staminal ring - in eucalypts, the narrow ring-like structure to which the stamens are attached; also called a staminophore
staminode - a sterile stamen, one without an anther, or with a reduced, non-functional anther
staminophore - see staminal ring
stigma - pollen-collecting structure at the tip of the style
style - the filament surmounting the ovary, through which the pollen tube travels from the stigma
subgenus - a natural group between genus and section, used in the classification of plants
subspecies - a form of a species having a minor but distinct- ive morphological identity (compared with the typical form of the species), and which occupies a particular habitat or region, geographically or altitudinally, for example, apart from the typical form
terete - round in cross-section
terminal (of inflorescence) - occurring at the end of a branchlet
tessellated (of bark) - surface marked into squares, or oblong scales or blocks
truncate - cut off, as in a truncate-globose fruit, that is, spherical minus a small section
valve - a sector of the roof of the capsule, which is formed in dehiscence and is usually raised to allow the escape of seed and chaff
venation - the pattern of the veins of the leaves
During the compilation of the notes above, and the species digests below, the following publications were consulted extensively:
BLAKELY, WF. (1955). A Key to the Eucalypts. Forestry and Timber Bureau, Canberra.
BOLAND,DJ, BROOKER,MIH, and TURNBULL,JW. (1980). Eucalyptus Seed. CSIRO, Canberra.
BOLAND,DJ, BROOKER,MIH, CHIPPENDALE,GM, HALL,N, HYLAND,BPM, JOHNSTON,RD, KLEINIG,DA, and TURNER,JD. (1984). Forest
Trees of Australia. CSIRO, Canberra.
BROOKER,MIH, and KLEINIG,DA. (1990). Field Guide to Eucalypts.
Volume 1 (Revised) and Volume 2. Inkata Press, Melbourne,
BROOKER,MIH, and KLEINIG,DA. (1994). Field Guide to Eucalypts.
Volume 3. Inkata Press, Sydney.
BROOKER,MIH. (in press). A New Classification of the Genus
FLORENCE,RG. (1983). A Perspective of the Eucalypt Forests:
Their Characteristics and Role in Wood Production. New
Zealand Journal of Forestry, 28(3): 372-393.
HALL,N, JOHNSTON,RD, and CHIPPENDALE,GM. (1970). Forest Trees
of Australia. Australian Government Publishing Service,
MULLIN,LJ. (1996). Eucalyptus in Zimbabwe. Kirkia 16(1): 95- 107.
PRYOR,LD. (1976). Biology of the Eucalypts. Studies in Biology No. 61. Edward Arnold, London.
PRYOR,LD, and JOHNSON,LAS. (1971). A Classification of the
Eucalypts. The Australian National University, Canberra.
The idea of describing the eucalypts of Harare was first suggested to me by Tom Muller in about mid-1994. Records show that 75 species have definitely been planted within greater Harare and its immediate environs, and there is reason to believe two other species may have been planted in the past, making 77 in all. One species, E. camaldulensis, is repres-ented by two subspecies, to make a total of 78 taxa known or believed to have been planted within the city environs (see Appendix 1). Many of the plantings are known to have failed, but 27 species are definitely present within the city limits, or within easy access of the city, and these are described in the notes following. I include 10 other species that I feel are probably present in Harare, and it is simply a matter of finding them. The 37 species described in the following pages are dealt with in taxonomic order, and any additional species that may come to light as time goes on will be described with notes indicating where they fit in.
In order to keep the species digests reasonably brief I omit notes on seedling, juvenile, and intermediate leaves; even though these stages in leaf development have good diagnostic value in identifying species, they are generally unlikely to be seen by members of the Tree Society. However, in the case of E. cinerea the juvenile and intermediate leaves are described because the species usually reaches maturity in the juvenile-leaf stage.
The arrangement of stamens in the flower bud, before the operculum is shed, varies between groups of species, and is of considerable diagnostic value, but, here again, most members of the Tree Society are unlikely to spend time disecting flower buds to examine the stamens, and so for the sake of brevity notes on these characters are omitted.
The taxonomy and relationships of each species described here follows MIH Brooker's classification, but only a brief outline is included to provide some idea of how the huge genus Eucalyptus has been fitted together by a leading taxonomist. The outline is only the briefest glimpse, for Brooker's draft classification runs to 55 (A4) pages, plus 21 pages of introduction, references, appendixes and index.
The general notes on each species are largely confined to its natural distribution and economic importance in Australia, and its introduction into Zimbabwe. Notes on wood properties are omitted for most species even though eucalypts were brought into Zimbabwe to provide plantation-grown timber; wood properties do not assist in the identification of a living tree, and notes on them would simply add to the length of a species' description.
EUCALYPTUS CALOPHYLLA R. Br. ex Lindley Marri
Habit: occasionally mallee on very infertile sites, but usually medium-sized to tall tree with dense, heavily branched crown; bole up to one-third of tree height.
Bark: grey-brown to dark brown, rough, tessellated, short-fibred, persistent to smaller branches (ie not shed), often stained in patches to reddish hue by exudation of kino.
Adult leaves: petiolate, alternate, ovate to broad-lanceolate, 90-140 x 25-40 mm, strongly discolorous, glossy dark green above, paler below, thick; venation fine, with regular parallel veins at 50-70 degrees to midrib, reticulation very dense; small round oil glands, one gland per smallest unveined area of leaf; intramarginal vein close to margin.
Inflorescences: large terminal corymbose panicles, 7-flowered (3-7); peduncles terete to angular, 13-45 mm long; buds pear-shaped to globose or club-shaped, 8-15 x 5-9 mm, no scar; operculum hemispherical, often with small conical protuberance in middle, sometimes slightly beaked; flower clusters large, white to creamy white, rarely pink, January-March.
Fruits: pedicellate, urn-shaped, 26-50 x 22-40 mm, thick, woody; rim thin; disc broad, descending; valves 4, deeply enclosed; seed black, no wing.
Derivation of names: botanical - from Greek calos (beautiful), plus phyllon (leaf); common - of Aboriginal origin.
Taxonomy: Subgenus Corymbia - woody fruited bloodwoods.
Section Notiales - bark rough throughout, tessellated; leaves strongly discolorous; outer operculum persisting to flowering; of southwestern and southeastern distribution only [Latin notialis (southern) refers to species distribution].
Series Cymbaliformes - seeds lacking a wing, boat-shaped; bark regularly tessellated; leaf oil glands present or lacking; filaments white or pink.
Related species: 3 species in series, the other two being
E. gummifera and E. haematoxylon; last-named very closely related to E. calophylla, but not quite at supraspecies level.
General: widely distributed in southwestern Australia in winter-rainfall zone; its range slightly overlaps that of
E. ficifolia. Grown ornamentally in Harare, one specimen known in Belvedere. There is a fine specimen at Rhodes Nyanga Hotel, between car park and hotel verandah. E. calophylla is distinguished from all other woody-fruited bloodwoods by its very large buds and fruits, and from E. ficifolia by its white or creamy white flowers, and the oil glands in the leaves.
EUCALYPTUS FICIFOLIA F. Muell. Red-flowering gum
Habit: usually small straggly tree, poorly formed and heavily branched from near ground level, often without distinct trunk.
Bark: grey, brown, or red-brown, yellowish beneath surface, longitudinally furrowed, persistent to smaller branches.
Adult leaves : petiolate, alternate, broadly lanceolate, 70-140 mm x 20-60 mm, strongly discolorous, dull or glossy green above, paler below, thick, almost leathery; venation fine, regular, parallel, at wide angle to prominent midrib, densely reticulate, intramarginal vein close to margin, no gland dots.
Inflorescences: terminal panicles, usually 7-flowered (3-7); peduncles 20-33 mm long, terete or angular; pedicels 17-36 mm long, slender; buds ovoid to club-shaped, 12-16 x 6-8 mm, no scar; operculum conical to slightly beaked; flowers in spec-tacular clusters of red, scarlet, or orange, December-March.
Fruits: pedicellate, barrel-shaped, or slightly urn-shaped, 20-42 x 20-31 mm, thick, woody; rim thin; disc wide, descend-ing; valves 4-5, deeply enclosed; seed yellow-brown, winged.
Derivation of names: botanical - from superficial resemblance of the dark green leaves, with their prominent midribs, to those of some species of fig, Ficus; common - from colour of flowers.
Taxonomy: Subgenus Corymbia - woody-fruited bloodwoods.
Section Notiales - (see E. calophylla).
Series Disjunctae - seeds with terminal wing; bark fibrous or somewhat tessellated; leaves lacking oil glands; filaments orange or red, rarely white; Latin disjunctus (disjunct) refers to distribution being distant from species with similar seeds.
Related species: somewhat isolated taxonomically; the only species in its series, therefore no close relatives. It will hybridize with E. calophylla, however, to produce plants that have rose-coloured or pale yellowish pink flowers.
General: a winter-rainfall species of very restricted natural distribution near Albany on southwest coast of Australia, but a widely cultivated ornamental outside Australia. Occasional specimens seen in and around Harare, and there is a plot at the Forest Research Centre off Orange Grove Drive. Better-developed trees occur in Nyanga National Park, near Warden's office; outstanding specimen at old homestead on Magakooshla Estate near Shurugwi. When not actually in flower it may be confused with E. calophylla, but the latter is a larger tree with gland-dotted leaves, and larger and more urn-shaped
EUCALYPTUS TORELLIANA F. Muell. Cadaga, Cadaghi
Habit: medium-sized to tall forest tree, usually with well-formed bole up to two-thirds of tree height; branching generally thick and heavy.
Bark: grey to black, scaly, sub-tessellated on lower part of bole, decorticating above to leave a slaty green or slightly shiny green surface.
Adult leaves: petiolate, alternate, broadly lanceolate to lanceolate, 100-140 x 17-35 mm, glabrous, green, slightly discolorous; venation distinct, at 45-55 degrees to midrib, densely reticulate; numerous small oil glands. Adult leaves comparatively rare, many trees having only juvenile and intermediate leaves (juvenile leaves peltate, broadly ovate, 120-220 x 80-140 mm, green, discolorous, petioles and leaf veins with many simple hairs; intermediate leaves ovate to broadly lanceolate, 90-160 x 35-65 mm, only slightly hairy, becoming glabrous, green, discolorous).
Inflorescences: large terminal corymbose panicles, 3-7- flowered; peduncles terete, 5-20 mm long; pedicels absent or only up to 3 mm long; buds ovoid, 8-9 x 5-6 mm, scar present; operculum hemispherical-apiculate, dark brown, contrasting with lighter brown of hypanthium; flowers white or creamy white, August-October.