Small tree usually to <5 m, exceptionally to 10 m. Crown spreading, irregular. Bark scaly on largest stems, greenish on young wood. Branchlets spreading to assurgent, with leaves clustered on shaded shoots, more evenly spaced on young shoots. Terminal buds ovoid, abruptly narrowing at the apex to a slender point, or somewhat truncate, 2–4 × 3–4 mm, with free triangular scales. Leaves on juvenile plants linear-lanceolate, straight, to 9 × 1–1.3 cm, apex acute to rounded. Leaves on adult plants oblong to linear, (2–)3–5(–7) × 0.5–0.8(–1) cm, spreading or assurgent, very densely set, base short-petiolate and twisted, apex obtuse to rounded, margins somewhat revolute, midrib acutely raised on upper surface, obtsusely raised below forming a ridge c. 1 mm wide; undersides with irregular narrow bands on stomata. Pollen cones solitary, sessile, short-cylindrical, 8–30(–35) × 6–8 mm at maturity. Seed cones borne near the end of foliage branchlets, pedunculate; receptacle 10–14 mm, subtended by 2 bracts 1–1.5 mm long, reddish-purple ripening dark pruinose-purple. Seeds ovoid, covered in a greenish or pruinose epimatium, dark blue at maturity, 8–10 × 6–7 mm. (Farjon 2017; Fu, Li & Mill 1999).
Distribution Philippines Bucas Islands to the Batan Islands, possibly NE Luzon Taiwan Lanyu Island (off SE coast)
Habitat Lowland forests and coastal scrub, often on karst limestone including sea stacks; 0–300 m asl.
USDA Hardiness Zone 8b-9a
RHS Hardiness Rating H3
Conservation status Endangered (EN)
From its natural distribution it might seem improbable that Podocarpus costalis could grow even on the most forgiving fringes of our study area of the northern temperate zone, but grow it does, to c. 1 m at Tregrehan (Cornwall, UK) after 15 years (pers. obs. 2022). These plants are traceable to one of several sporadic distributions of Index Seminum seed by the Taiwan Forestry Research Institute, distributions which have seen the species become established in collections in the more conducive climate of Australia. Plants were raised from the most recent Taiwan distribution in 2008, under IS item number 50, by several collections in our area, including Logan Botanic Garden in SW Scotland, but young plants in propagation there could not be located during a research visit in late 2022 (pers. obs). It is represented at the Montgomery Botanical Center in Florida by plants of uncertain provenance (Royal Botanic Garden Edinburgh 2023).
This is a rare plant in the wild, limited to only a few localities and very specific habitat. Its decline is largely due to the removal of plants from the wild for gardens, mainly in the Philippines and in Taiwan, where it is valued as an ornamental (Carter & Farjon 2019).
According to Farjon (2017) several authors have assigned plants from Taiwan to this species, but it does not occur there. Plants from Taiwan labelled P. polystachyus probably belong to P. costalis (Fu, Li & Mill 1999). This is probably the case for any plants grown in our area under P. polystachyus, except perhaps a few under glass in major collections.