Beauty, they say, lies in the eyes of the beholder. In the eyes of landscape architects and garden designers beauty often lies in the shape of trees. Broad spreading trees can give shade and a fine tracery of foliage. More compact crown shapes may provide a formal architectural element to planting schemes.

Tightly columnar trees are particularly useful for offering focal points in landscape designs and also in providing greenery in planting sites of limited width. In Singapore there has been a recent resurgence of interest in columnar varieties because of the need to grow trees in ever-narrower parcels of land and the appearance of some new species suited for this use.

MENINJAU
A columnar tree, possibly native to Singapore but cultivated here for many centuries, is the meninjau (Gnetum gnemom). The gnetums are a botanical oddity. They are gymnosperms, like conifers and cycads, but vegetatively seem much more similar to typical flowering plants particularly in possessing ‘normal’ leaves rather than needles or fronds. It is still not clear whether the gnetums are the linking group between the angiosperms and the gymnosperms, or whether superficially similar plants arose on two different evolutionary lines. Gnetum gnemom is cultivated in kampongs throughout Southeast Asia not for its ornamental but for its economic value, particularly for its edible leafy shoots and ‘fruits.’ The latter can be made into a sort of flour most famously used to prepare the fried crackers known as keropok or embing. Meninjau trees are naturally columnar, with short side branches coming out almost horizontally from the main trunk. The glossy foliage and strong shape of the tree make it suitable for use in landscaping. Several roads in Singapore are successfully planted as meninjau avenues. Male trees (meninjau trees come in separate sexes) are better for roadside planting as they do not drop squashy seeds.

TEMPLE PIKA
The ashoka tree has been planted in Singapore since the 1960s. It is a columnar form of Polyalthia longifolia – a tree native to southern India and Sri Lanka. In its common or typical form, Polyalthia longifolia is quite a spreading tree and is to be found as an ornamental in many tropical locations. Ashoka seems to differ from the typical form purely in its branching. The branches are short and pendulous resulting in a very tight pillar of foliage. A well-grown tree can exceed 10m in height and provide a beautifully straight and narrow column of green. Unfortunately, the ashoka has a tendency to bend and buckle which probably explains its decline in popularity over recent years. However, if well maintained, it is probably superior to the others.

CARALLIA BRACHIATA ‘HONIARA’
Another recent addition, also from the western Pacific region, is Carallia brachiata ‘Honiara’. Introduced to Singapore from the Solomon Islands in 1986, it is a weeping form of a widespread forest tree Carallia brachiata. Not quite as narrow or regular as the other three, it has a certain grace to its weeping branches and provides a much-needed softening touch when planted next to high-rise buildings.

GARCINIA
The newest columnar tree around is Garcinia cymosa forma pendula, generally referred to under the name Tripetalum cymosum. As the only notable difference between Tripeatalum and Garcinia is a flower with 3 petals instead of 4 or 5, the former is best included in the latter. Garcinia cymosa forma pendula has traditionally been grown in villages in its native New Guinea. It is another example of a crown-form mutation being favoured in cultivation. The columnar form has weeping, pendulous branches that produce an almost untapered pillar of foliage. The bright red fruits are also attractive.

A BOTANICAL NAME FOR THE ASHOKA TREE
The ashoka tree lacks a botanical name. A number of books refer to it as Polyalthia longifolia var. pendula, but this name has never been validly published. A cultivar name is most appropriate as the plant only seems to be known from cultivation. Therefore I here provide a name and diagnosis of the columnar form.

POLYALTHIA LONGIFOLIA (SONN.) THWAITES ‘TEMPLE PILLAR’
A tightly columnar form apparently indistinguishable from the typical form except in branching. The side branches remain relatively short (about 1m long), branch little, and are held about 45o below the horizontal. The photographs accompanying this article are designated as the standard for ‘Temple Pillar’ as a herbarium specimen gives limited information on crown form. The cultivar name chosen reflects the frequently reported practice of growing this tree near temple in Southern India.

Ian Turner
Horticulture Branch
(From Gardenwise-The Newsletter of the Singapore Botanic Gardens Vol XV, July 2000 ISSN 12-1688)