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Podocarpus is the second largest genus of conifers after Pinus, with 107 species (Farjon 2001). Most are limited to the southern hemisphere: subgenus Podocarpus occurs in the temperate forests of New Zealand, Tasmania and Chile, extending into the tropical highlands of Africa, South America and New Caledonia; subgenus Folio latus occurs primarily in the Asian-Pacific tropics. Podocarpus species are dioecious (rarely monoecious) evergreen trees or shrubs. The leaves are spirally arranged to subopposite, though they often appear crowded or two-ranked; there are minimal differences between adult and juvenile forms, though juvenile leaves tend to be larger and/or wider. The leaves are flattened, linear, lanceolate or oblong, with a distinct midrib. Male strobili are sessile or stalked, solitary or grouped, and produced in the axils of the upper leaves. Female cones are axillary (rarely terminal) and solitary; composed of a single fertile scale bearing one to two (to three) ovules, subtended by several sterile scales, which are usually fused together to form a receptacle. The receptacle becomes fleshy or leathery, and brightly coloured in some species, while in others it is obsolete; the epimatium completely encloses the seed, and may also become fleshy and brightly coloured (Hill 1998, Fu et al. 1999b). A taxonomic revision of this large genus has been produced (de Laubenfels 1985), but many of the species are poorly known.
As generic concepts have developed, many species formerly in Podocarpus have been placed in distinct genera. Synonyms are given below where appropriate, but Farjon’s World Checklist and Bibliography of Conifers (2001) offers a more complete guide. A number of tropical species, including several in segregate genera, were described by Krüssmann (1985b), but have little if any chance of being hardy in our area.
For horticultural purposes Podocarpus falls into two broad groups: low shrubs, mostly from Australasia; and true trees, from forest areas around the southern hemisphere. The shrubby species should not be ignored as they are often very useful and attractive ground-covering plants. In recent years, largely through the efforts of Graham Hutchins of County Park Nursery, Hornchurch, Essex, a considerable range of selections from P. lawrencei, P. nivalis and hybrids between them (and, to a lesser extent, from P. cunninghamii (syn. P. hallii) and P. acutifolius) have been released into the horticultural trade. Among these, ‘County Park Fire’ (P. lawrencei P. nivalis) is widely available and offers a gamut of colours, from the yellow to salmon-pink of the new shoots to the purple-bronze of the foliage in winter (Hutchins 1996).
Podocarpus is a familiar and important constituent of the cooler, moister forests of the southern hemisphere, and can form large and magnificent timber trees of considerable significance in the forest ecosystem. In particular the swollen receptacle of the ripe fruit, which is often red and becomes sweet-tasting, is an important food source for many birds, which later disperse the seeds. On Kilimanjaro the big ‘podos’ P. milanjianus growing in the upper levels of the Afromontane forest are much favoured by Red-fronted Parrots (Poicephalus gulielmi), Hartlaub’s Turaco (Tauraco hartlaubii) and Olive Pigeons (Columba arquatrix) (JMG, pers. obs.). All follow the sequence of tree species coming into fruit around the mountain, and will migrate to other forest areas in search of food. This goes a long way towards explaining the wide distribution of many Afromontane trees, including P. milanjianus – found on mountains apparently isolated by vast tracts of lowlands, but no obstacle to a fast-flying pigeon.
In addition to the podocarps described below, hybrids between the frequently cultivated Chilean P. salignus and the New Zealand species P. totara and P. cunninghamii have occurred on several occasions where the parents are grown together in UK gardens (Allnutt et al. 1997).
Podocarpus nubigenus Lindl. has been introduced to the Royal Botanic Garden Edinburgh on several occasions in recent decades as a result of collaboration with Chilean institutions. It is a potentially large, columnar tree up to 30 m tall and provides excellent timber, to the extent that it is a subject of conservation concern (Near Threatened, according to Gardner et al. 2006, although categorised by the IUCN as Lower Risk). Seedlings have been raised at Edinburgh using an embryo excision technique that has given greatly enhanced results (Brownless et al. 1997). Resulting plants are now in cultivation in the Scottish botanical gardens and the Bedgebury National Pinetum in Kent. They grow slowly when young, but those at Benmore are now up to 2 m tall and growing steadily, appreciating the wet conditions there and proving fully hardy (M. Gardner, pers. comm. 2008).
The related Nageia Gaertn., of which N. nagi (Thunb.) Kuntze has long been cultivated under glass (see Bean and Krüssmann: B283, S387, K260), is a genus whose members might now be more successful outdoors in mild gardens. In addition to N. nagi, N. fleuryi (Hickel) de Laub. from southern China and Indochina, and the Taiwanese N. formosensis (Dümmer) C.N. Page are grown at the Royal Botanic Garden Edinburgh and elsewhere, and are candidates for planting outside in favoured sites (P. Thomas, pers. comm. 2007).
Propagation of Podocarpus is by seed, which can be slow and erratic to germinate when sown in a normal way (P. Thomas, pers. comm. 2007), but embryo excision, though requiring considerable care, can give much better results (Brownless et al. 1997). Cuttings from firm young shoots are usually successful but may be slow to root. As young plants Podocarpus should not be exposed to hot bright sunshine, as most start life as understorey plants in the wild. Trees can be slow to establish, but respond well to the application of slow-release fertilisers. A moist acidic soil is generally preferred, but the alpine shrubs seem not to be fussy and tolerate both lime and drier conditions.
A genus of about 100 evergreen trees and shrubs, with its main distribution in the warm-temperate and subtropical rain-forests of the southern hemisphere, but extending as far north as the Himalaya and Japan. Some species are important timber trees in their native countries. They are variable in their foliage, but all the main types are represented in the species described here. Male inflorescences cylindrical, catkin-like, usually in stalked or sessile axillary clusters, or solitary; or arranged in spikes (sect. Stachycarpus). The female inflorescence consists of a short axis, bearing a few scales of which only the upper one or two are fertile. The seed is much larger than the subtending scale, nut-like or drupe-like, coated by an excrescence of the carpel (epimatium). In the typical section (sect. Podocarpus) the inflorescences are borne in the leaf-axils, and the upper sterile scales become united with the stalk and develop into a fleshy, coloured receptacle on which the seed is borne; the seed is nut-like. To this group belong all the species treated, except those mentioned below. In the section Stachycarpus the female inflorescences are arranged in a spike; there is no fleshy receptacle, but the seed itself develops a more or less fleshy layer on the outside. To this section belong P. andinus, P. spicatus, and P. ferrugineus, though the last is anomalous in having usually solitary fruits. The section Nageia is distinguished mainly by its broad leaves. The female inflorescence and fruit resembles that of the typical section, though, as in P. nagi, the receptacle sometimes remains dry.
Propagation is by seed if procurable, or by cuttings taken in late summer.
The generic name comes from the Greek pous, foot, and karpos, fruit, in allusion to the fleshy receptacle mentioned above.
The family Podocarpaceae, though in part only, was reviewed by D. J. de Laubenfels in ‘A Revision of the Malesian and Pacific Rainforest Conifers …’, Journal of the Arnold Arboretum, Vol. 50, pp. 274-369 (1969). In this paper he gives generic rank to the section Nageia, publishing for it the new generic Decussocarpus, though it is surely arguable that the proposed genus already had a name – Nageia Gaertner.
It was not mentioned in the main work that P. dacrydioides (page 280) belongs to a group – section Dacrycarpus – which is distinct from the rest of the genus in the form of its fruits. In these the bract-scale (carpidium) is as long as the seed and fused with it on one side. In the other sections the bract-scale remains small, and the outer coating of the seed is formed only by the epimatium (ovuliferous scale). The foliage too is distinct from that of most other members of the genus, resembling that of Dacrydium in the species mentioned and in others not unlike that of Cryptomeria. This section too has been raised to generic rank by de Laubenfels as Dacrycarpus.
In another Paper (Blumea, Vol. 24, pp. 189-96 (1978)) de Laubenfels proposes the resurrection of the genus Prumnopitys, which is founded on the mainly Chilean species Podocarpus andinus. The group concerned constitutes (in Podocarpus) the section or subgenus Stachycarpus, with some other species in South America and the remainder in Australasia and the south-west Pacific.
There is no doubt that the Podocarpaceae are in need of reclassification. But it seems better to leave the present arrangement as it stands until the whole family has been studied and, where necessary, regrouped according to consistent taxonomic criteria. See also Dacrydium in this supplement.
The genus Podocarpus, with the exclusions mentioned above, is revised by de Laudenfels in Blumea, Vol. 30, pp. 251-78 (1985).