Pittosporum dallii Seeds | Pittosporum
LATIN NAME: Pittosporum dallii
COMMON NAME: Pittosporum
Plant Profile
Bullate leaves come from uneven expansion of the blade: the tissue between the veins grows faster than the veins themselves, so the surface is pushed into blisters and the leaf keeps its shape even when it dries. In this species the effect is combined with a finely toothed margin and a thick, glossy cuticle, giving a leaf that survives mountain wind and high ultraviolet while looking like something from a wetter forest. The shrub is compact and rounded rather than upright, branching densely from low down. Old leaves stiffen and darken, and the shrub carries several seasons of foliage at once, so the quilted texture stays visible on the lower branches as well as at the tips.
The wild populations are few, scattered and confined to one mountain district, which places the species among the threatened plants of New Zealand and makes garden material a genuine conservation resource rather than a curiosity. Seed is short-lived, so work away from the wild leans on fresh sowings, on a small number of nursery lines, and on the seed banking that New Zealand applies to its threatened flora. A grower holding a plant holds something with a provenance worth recording. Cuttings taken from semi-hard wood in late summer strike slowly but root dependably in a cool, humid frame, and they carry that provenance with them.
Science & Biotechnology
The family Pittosporaceae is characterised by triterpenoid saponins and by volatile oils in the flowers, and the genus has been screened mainly in its Australian and Asian species. For this New Zealand endemic the published chemical work is thin, and there is no honest case for claiming medicinal virtues: it is a rare mountain shrub with a distinctive leaf and a sticky seed. Treat any stronger claim with suspicion.
Uses & Benefits
Flowers are small, cream to white and held in loose clusters, carrying the honey scent that runs through the genus. The fruit is a woody capsule that splits into two valves, and the seeds inside wear a sticky, resinous film: pitta for pitch and spora for seed, exactly what the genus name describes. That gum is the dispersal mechanism, because seeds adhere to the feet and feathers of visiting birds, so the plant travels short distances without wind or a fleshy reward. The same stickiness makes the seed awkward to handle and short-lived.
Growing from Seed
Where summers are cool and moist, this shrub makes a slow, dark specimen for a rock garden or the front of a shrub border, and it is frost hardy provided drainage is sharp and the site is not scoured by drying wind. It dislikes the heat and humidity that suit the coastal pittosporums, so it belongs with other southern highland shrubs rather than in a warm courtyard. Site it where the bullate foliage is seen from above, on a slope or in a raised bed. Shelter young plants from drying wind for their first two winters, and the reward is a shrub that looks better in its fifth year than in its first.
Sow as soon as the seed is cleaned, because the resinous coat deteriorates in storage. Rub the film off in a little damp sand, sow into a gritty blend of loam, leaf mould and sharp grit, cover lightly with the same mix, and keep the pan in a cool, shaded frame. Prick the seedlings out when they show two true leaves, using a deep pot, and handle the roots carefully because the young plant resents disturbance. Plant out when the top growth reaches about fifteen centimetres.
The main danger is a warm, wet root zone, where collar rot moves quickly and a plant can collapse without warning; free drainage and a gravel collar around the stem are the whole of the prevention. Scale insects and whitefly settle on the sheltered leaf undersides under glass, and in New Zealand gardens possums and deer browse young shoots, so protect the plant while it establishes. Mulch with coarse bark rather than compost to keep the collar dry.
Our Take
Grow this one for the leaf and for the fact that it is rare: a plant that asks for cool air, sharp drainage and nothing else. Gardeners who admire the genus for its hedging and scent should look at Pittosporum tobira, and the southern-hemisphere theme is carried further by the kauri page on Agathis australis and by the dove tree entry for Davidia involucrata.
Related Reading
Gardeners who grow Pittosporum often pair it with these related subjects: