Carpinus cordata Seeds | Heart-leaved Hornbeam
LATIN NAME: Carpinus cordata
COMMON NAME: Heart-Leaved Hornbeam
Plant Profile
Heart-leaved hornbeam is a deciduous tree of the birch family, ten to fifteen metres in the wild and usually smaller in a garden, with a rounded crown, slender branches and smooth grey bark that develops shallow flutes and muscle-like ridges with age. It belongs to the same genus as the European hornbeam, and it shares that tree’s hard timber and its tolerance of clipping.
The leaves are the distinguishing feature, and they are the largest in the genus: up to fifteen centimetres long and eight wide, broadly heart-shaped at the base, with prominent parallel veins and a doubly toothed margin. They are deep green above, softer and slightly hairy beneath, and they turn a clean yellow in autumn. On a young tree the effect is almost tropical, which is not what most people expect from a hornbeam.
The flowers are catkins, as in the rest of the family. The male catkins are long and pendulous and appear before the leaves, the female ones are short and upright and develop into the hop-like clusters of bracts that hang through autumn, each bract enclosing a small nut. Those clusters are the second ornamental reason to grow the tree, and they last well into winter.
Its range covers Japan, Korea, northeastern China and the Russian Far East, in cool, moist, mixed broadleaf forest on rich, well-drained soil. It is a tree of the understorey and the forest edge rather than of the open landscape, and it tolerates more shade than most hornbeams.
Science & Biotechnology
The genus Carpinus is a familiar one to wood anatomists, because its timber is among the hardest and densest in the temperate flora. The wood has very small vessels, thick-walled fibres and a high density, which is why it was used for tool handles, mallets, cogwheels and piano actions before metal and plastic replaced it. Heart-leaved hornbeam shares that anatomy, though its timber is less exploited than that of the European species.
The species sits in the section of the genus with large leaves and few veins, close to Carpinus fangiana and Carpinus turczaninovii, and the group is centred in China and Japan. Molecular work has clarified the relationships within the genus but has also shown that hybridisation occurs where species meet, particularly in the Chinese mountains, which complicates the delimitation of the eastern taxa.
The seed is a small nut enclosed in a leafy bract, and the bract acts as a wing, so that the seed spins away from the parent tree in autumn. Dispersal is by wind and by gravity, and the seed requires cold, moist stratification to germinate, which is an adaptation to a climate with a long, cold winter and a short growing season.
Ecologically the tree is a component of the cool mixed forest, and its catkins are an early pollen source for bees, though the wind-pollinated flowers produce no nectar. The nuts are eaten by small rodents and birds, and the tree is one of the species that regenerates in the shade of larger trees and then waits for a gap.
Uses & Benefits
In the garden it is a specimen tree for a medium to large space, grown for its bold foliage and its autumn catkins rather than for flowers. It is a good substitute for the European hornbeam where a more dramatic leaf is wanted, and it can be clipped into a hedge, though the large leaves make a coarser hedge than Carpinus betulus. It is also a good tree for a woodland garden, since it tolerates shade.
The timber is hard, heavy and close-grained, and it is used locally for tool handles, furniture and turnery. It is not a commercial species in international trade, but it is valued in its native range for the same qualities that made European hornbeam a workshop standard.
The tree has no significant medicinal or culinary use. The nuts are small and not worth collecting, and the bark and leaves do not appear in the pharmacopoeias of the region. It is an ornamental and a timber tree, and that is the whole of its useful story.
Ecologically it is a useful species for a wildlife garden, since the catkins provide early pollen and the seed clusters provide cover and food for small birds through the winter. It is also a good host for lichens and mosses on its bark in humid climates, which is a small sign of clean air.
Growing from Seed
Seed needs cold, moist stratification: mix it with damp sand and keep at two to five degrees for twelve to sixteen weeks, then sow at one centimetre depth in a loose, humus-rich mix at fifteen to twenty degrees. Germination is usually four to eight weeks after the cold period, and it can be uneven, so keep the tray for a second spring.
Grow the seedlings in partial shade for the first two years, in a rich, moist but well-drained soil, and pot them on as they grow. Plant out into a sheltered site with deep soil, and water through the first two summers. The tree is slow to establish but long-lived, and it needs little pruning beyond the removal of low branches and the cutting out of any dead wood in winter.
Our Take
Heart-leaved hornbeam is the hornbeam for a gardener who wants something bolder than the usual hedge plant: bigger leaves, longer catkins and the same tough, hard-wooded constitution. Give it deep soil, some shade and room to spread, and it will reward you with a foliage effect that looks borrowed from a warmer place.
Related Reading
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