Pinus pumila Seeds | Japanese Stone Pine
LATIN NAME: Pinus pumila
COMMON NAME: Japanese Stone Pine
Plant Profile
Japanese stone pine is a shrub, not a tree, and it is one of the very few pines that has committed entirely to a creeping, mounded habit. The stems lie along the ground and root where they touch, rising at the tips into short, dense, blue-green tufts of five-needle bundles, so that a single plant becomes a low dome two to four metres across and rarely more than a metre and a half high.
The cones are small, oval and purple-brown, four to six centimetres long, and they sit among the needles rather than on long stalks. The seed inside is large, wingless and edible, and it is harvested in Japan and Korea, where it is sold as a delicacy and used in confectionery. The nuts are produced irregularly, and a good crop is a event that animals and people both notice.
Its range is the alpine and subalpine zone of Japan, Korea, northeastern China and eastern Siberia, where it forms the treeline scrub that marks the upper limit of tree growth. It grows in wind-blasted, snow-covered, rocky ground, and it survives there by staying low, by rooting as it spreads, and by tolerating burial under snow for eight months of the year.
For gardeners, the appeal is the combination of a genuinely dwarf pine, a blue-green colour that holds through winter, and a constitution that laughs at cold and wind. It is one of the best conifers for a rock garden, a large container or a windswept bank.
Science & Biotechnology
The creeping habit is an adaptation to the treeline, and it works on several levels. Staying below the snow surface protects the buds from ice-blasting and from desiccation, rooting at the nodes allows the plant to spread laterally and to colonise ground that is too exposed for a seedling, and the dense needle cover reduces water loss. The same strategy is used by dwarf willows and birches at the same altitude, which is why the treeline scrub of East Asia looks the way it does.
The species is a five-needle pine, in the same group as the stone pines and the whitebark pine, and it is closely related to Pinus cembra and Pinus sibirica. The group is characterised by wingless or nearly wingless seed, which is dispersed by animals rather than by wind, and by a tolerance of severe cold that few other pines can match.
The seed is dispersed by nutcrackers and by rodents, which cache it in the ground and forget a proportion, and that caching is what allows the pine to colonise new ground above the treeline. The relationship is a classic example of scatter-hoarding mutualism, and it has been studied in Japan and in Siberia for decades.
The timber is small and shrubby and of no commercial value, but the species is important ecologically as a stabiliser of alpine soils and as a nurse plant for tree seedlings. In Japan it is also a cultural plant, appearing in the planting of alpine gardens and in the bonsai tradition, where its tight needles and slow growth are highly valued.
Uses & Benefits
In the garden it is a specimen for a rock garden, a raised bed, a large container or a windswept slope, where its low dome and blue-green needles can be seen at close range. It is extremely hardy, tolerant of wind and poor soil, and it needs no pruning to keep its shape. It is slower than most garden conifers, which is exactly what makes it useful in a small space.
The seed is edible and is collected in Japan and Korea, where it is known as a delicacy and used in sweets and in rice dishes. The harvest is small-scale and irregular, and it is one of the traditional autumn foods of the mountain villages. The nuts are oily and sweet, similar to those of the Siberian pine but smaller.
It is also a bonsai subject of high quality, and it has been cultivated in pots in Japan for centuries. The tight needle arrangement, the short internodes and the natural mounding habit make it one of the easiest pines to train, and old specimens are highly prized.
Ecologically the shrub is a treeline engineer: it holds soil on steep slopes, it shelters seedlings of other species, and its seed feeds birds and rodents through the winter. In the mountains of Japan it is also the habitat of several rare insects and lichens, which depend on the stable, long-lived scrub that the pine creates.
Growing from Seed
Seed needs cold, moist stratification for eight to twelve weeks, followed by sowing one centimetre deep in a gritty, acidic, free-draining mix at fifteen to twenty degrees. Germination is usually four to eight weeks and can be uneven. Fresh seed germinates far better than stored seed, and the empty seeds are difficult to detect, so sow more than you need.
Grow the seedlings on in full sun, in a deep pot with sharp drainage, and do not overwater. Plant out into a raised bed or a rock garden with gritty, acid soil, and mulch with gravel to keep the collar dry. The plant is slow, so buy or raise a specimen large enough to be seen, and give it a site where it will not be shaded out by faster neighbours.
Our Take
Japanese stone pine is the conifer for a small, cold, exposed garden where a tree would be wrong and a shrub would be dull. It is slow, blue-green, indestructible in the right place and genuinely dwarf, and it will still be the same size in twenty years, which is more than can be said for most things sold as dwarf.
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