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The genus Ensete - an annotated list of species
by Gerda Rossel and David Constantine
or straight to the plants
The genus Ensete.
The
genus Ensete was first described by Paul (Paulo or Paulus) Fedorowitsch Horaninow
(or Horaninov) (1796 - 1865) in his Prodromus Monographiae Scitaminarum of 1862
in which he created a single species, Ensete edule. However, the genus did
not receive general recognition until 1947 when it was revived by E. E. Cheesman in the
first of a series of papers in the Kew Bulletin on the classification of the bananas.
Taxonomically, the genus Ensete has been getting smaller and smaller since
Cheesman revived the genus with 25 species. Cheesman acknowledged that field study
might reveal synonymy and the most recent review of the genus by Simmonds (1960) listed
just 6. Recently the number has increased to 7 as the Flora of China has re-instated
Ensete wilsonii. The species currently recognised (September 2000) are as
follows:
E.
gilletii
E. glaucum
E. homblei
E. perrieri
E. superbum
E. ventricosum
E. wilsonii
The composition of the genus Ensete is not settled definitively. For
example, Simmonds (1960) comments that he can see no consistent differences between E.ventricosum
and E. glaucum and that it might ultimately prove necessary to reduce the former
to the latter. Simmonds also treats E. wilsonii as E. glaucum.
Lock 1993 comments that E.gilletii may be no more than a subspecies of Ensete
ventricosum.
Cheesman (1947) and Simmonds (1960) mention one or two undescribed Ensete species
in Thailand which have still not been described but one is now in cultivation. Musa
martinii Noter from Vietnam might possibly be an Ensete. The Flora of
China mentions in passing that there are 10 species of Ensete. It
will be some time before anything like a complete picture emerges of Ensete or
indeed the Musaceae in south-east Asia.
Characteristics of Ensete.
The
genus has the following characteristics (Moore 1957, Simmonds 1960: 208 - 211; Champion
1967: 9):
| Habit |
Large
monocarpic herb. |
| Leaves |
Large,
oblong, gradual transition of the upper leaves into bracts. |
| Petioles |
Variable
in length, the lower ones sometimes shortest, giving the plant a rosette-like appearance;
when they are longer the plant has a more Musa-like appearance. |
| Leaf sheaths |
Lax,
loosely clasping the pseudostem. |
| Pseudostem |
Formed
by the leaf sheaths, somewhat swollen at the base, especially in E. homblei and E.
gilletii, but less so in E. ventricosum and E. glaucum. |
| Bracts |
Persistent,
covering 2 rows of flowers. |
| Bract insertion |
Flowers
and bracts are integrated at the base and with the floral axis; they have no abscission
layer (contrary to Musa) and the flowers and bracts persist on the axis although
they may shrivel as the inflorescence matures. |
| Inflorescence |
Drooping
at maturity; gradual transition in flower type from basal hermaphrodite (sometimes female)
to distal male flowers. Perfect stamens have been sometimes seen in basal flowers of
E. ventricosum, E. homblei and E. glaucum. |
| Flowers |
Outer
perianth (compound tepal) and inner perianth (free tepal). |
| Outer perianth |
3
linear lobes which are coherent at the two adjacent margins but are not fused or fused at
the base only; two small accessory lobes may or may not be attached at the middle of the
edges of the central lobe. |
| Inner perianth |
A three-lobed structure, about as broad as long (sometimes
replaced by three separate lobes in E. ventricosum), with a narrow central
segment which is acute or long-apiculate at the tip and which contains the midvein of the
tepal; two suborbicular ragged-dentate lateral lobes enfolding the filaments. |
| Fruits |
Leathery
and dry with big seeds and scanty, whitish or orange-coloured pulp. |
| Seed |
Blackish,
spherical, with irregular and depressed hilum, T-shaped embryo, mean diameter; E.
glaucum 9 - 12 mm., E. superbum 8 - 12 mm., E. ventricosum 12 - 18
mm., E. gilletii 7 - 9 mm., E. homblei 6-7 mm. |
| Pollen |
Granulose-papillose,
with a thin exine. |
Differences between Ensete species.
Ensete
species can be divided into two geographic groups, African and Asian. The three
African species (E. gilletii, E. homblei and E. ventricosum)
differ mainly in the size of the plants and the seeds, as well as in the orientation of
the leaves. The two Asian species (E. superbum and E. glaucum)
differ in the circumference of the lower pseudostem and the colour of the bracts (Simmonds
1960: 212; Baker & Simmonds 1953: 407-408, 414). [The Madagascan E.
perrieri is too little known to be included in this discussion].
Simmonds has drawn attention to similarities between Asian E. glaucum and African
E. ventricosum for instance in waxiness, structure of the bracts and flowers,
colour of the sap and in seed characters. The only constant difference between the
two seems to be the pigmentation of the male flowers, which are all-white in E.
glaucum, while those of E. ventricosum have an orange-yellow tipped
perianth, violet or purple anthers and yellow or greyish pollen. Both have wide
geographic ranges but E. glaucum reportedly varies little whereas E.
ventricosum is highly variable.
Differences
from Musa.
The differences Cheesman highlighted to separate Ensete from Musa can be
summarised as follows:
Ensete |
Musa |
| Single
stemmed monocarpic herbs with pseudostems dilated at the base. |
Stooling
perennial herbs with cylindrical pseudostems. |
| Fruit
with a small number of large seeds (usually > 10mm) irregularly globose and smooth. |
Fruit
with a large number of small seeds (usually < 6mm) often irregularly and sharply
angular, rarely globose and smooth and, if so, then much smaller than Ensete and
easily distinguished. |
| Mainly
African in distribution but overlaps with Musa in Asia. |
No
native African species with an exclusively Asian distribution |
| Found
sometimes in grassy and rocky places at altitudes where the climate is cool |
The
commonest habitat is rain-forest country. |
| Haploid
chromosome number 9 |
Haploid
chromosome number 10 or more.
(This is no longer true; there are Musa sp. with haploid
chromosome numbers of 7 and 9.) |
Horticultural differences.
In
northern climes it is very unusual to see a flowering Ensete and the most useful
distinguishing characteristic horticulturally is that Ensete do not normally
produce suckers whereas all Musa do. But it is by no means impossible for Ensete
to produce suckers.
There
are reports of Ensete suckering in the wild. E. homblei possibly
suckers spontaneously although there is some question whether naturally suckering plants
may simply be colonies of seedlings. There are clones of E. ventricosum in
Ethiopia that do sucker spontaneously and this has also been noted in E. glaucum
in Vietnam. Ensete ventricosum will readily produce suckers if the growing
point is damaged artificially. This has been practised in Ethiopia for hundreds of
years as a means of propagating desirable clones and has recently been
"re-discovered" by nurserymen.
"Sucker" is not a very precise horticultural term and is defined as "a
shoot arising from a plant's roots or underground stem" (Griffiths 1994). The definition does not prescribe
the origin of the sucker shoot. Thus while the term sucker can be applied to both Ensete
and Musa there seems to be a fundamental difference between Musa and Ensete
suckers. In Musa, suckers arise from pre-existing lateral buds whereas, in
my experience, Ensete suckers seem only to develop adventitiously in response to
wounding. Thus in E. ventricosum, removal of the growing point does not
release previously inhibited lateral buds but results in the development of a callus mass
from which shoots spontaneously regenerate. The mechanisms by which suckers arise in
Musa and Ensete seem quite distinct. Musella seems to be
intermediate in the sense that suckers usually develop from lateral buds but can also
arise adventitiously from wound tissue at the base of detached suckers.
At
present (2002) only one Ensete is commonly propagated vegetatively, E.
ventricosum 'Maurelii'. It is increasingly common to find plants of this for
sale with suckers. This seems to be a by-product of the micropropagation process now
used in the commercial propagation of these plants.
A
much less certain method of separating Ensete from Musa is the length of
the petiole. Ensete tend to have short, indistinct petioles whereas in Musa
petioles tend to be long and obvious. However, like leaf shape and colouration,
petiole length is heavily influenced by light intensity. Ensete grown under
low intensity light have abnormally long petioles, narrow leaves and poor colouration.
This can cause some confusion for example when looking at plants in glasshouses at
botanical gardens.
Needs
revision
Distinguishing
Ensete species in cultivation based on foliage characters alone is likely to be
very difficult. At present the problem effectively does not exist since there is
only one Ensete species likely to be met with in cultivation or available
commercially, E. ventricosum and its red-leaved cultivar 'Maurelii'. The
status of another cultivar 'Montbeliardii' is not quite clear but it is probably no longer
extant. This situation however is changing. E. superbum
seed has been available for some time and seed of E. glaucum has just
become available. Seed of "Musa wilsonii" (= Ensete wilsonii)
from two collections at high altitude in China have also been offered commercially but
these seedlots are Musa not Ensete. It seems that these
two collections of "Musa wilsonii" are different plants, one looks like
Musa basjoo and the other may be Musa balbisiana but their identities
are currently not confirmed.
E. ventricosum is a very variable plant in nature and also in
cultivation as an ornamental. This is due partly to natural seedling variation but
also to seed of difference provenances being offered commercially. E. glaucum
has a very wide range but is reported not to vary much phenotypically. Its behaviour
in cultivation in temperate regions as an ornamental is not yet known. It may be
that different provenances will be significantly different in cold hardiness.
Ensete agharkarii
Ensete arnoldianum
Ensete bagshawei
Ensete buchanani
Ensete calospermum
Ensete davyae
Ensete edule
Ensete elephantorum
Ensete fecundum
Ensete gigantea
Ensete gilletii
Ensete glaucum
Ensete holstii
Ensete homblei
Ensete lasiocarpum
Ensete laurentii
Ensete livingstonianum
Ensete maurelii
Ensete nepalensis
Ensete perrieri
Ensete proboscideum
Ensete religiosum
Ensete ruandense
Ensete rubronervatum
Ensete schweinfurthii
Ensete sp. Thailand
Ensete superbum
Ensete ulugurense
Ensete ventricosum
Ensete ventricosum 'Atropurpureum'
Ensete ventricosum 'Green Stripe'
Ensete ventricosum 'Maurelii'
Ensete ventricosum 'Montbeliardii'
Ensete ventricosum 'Red Stripe'
Ensete ventricosum 'Rubrum'
Ensete ventricosum var. maurelii
Ensete ventricosum var.
montbeliardii
Ensete wilsonii
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