Tilia amurensis Seeds | Amur Linden
LATIN NAME: Tilia amurensis
COMMON NAME: Amur Linden
Plant Profile
The Amur linden is a tall, straight forest tree, fifteen to twenty metres in the open and taller in competition, with a dense, rounded crown and a trunk that stays clean for a good half of its height. The leaves are the classic linden shape: heart-shaped to broadly ovate, five to ten centimetres long, sharply toothed, dark green above and paler beneath, with small tufts of white hair in the angles of the veins, a character that separates it from its relatives at a glance. The bark is grey, smooth on young trees and furrowed into narrow ridges with age.
Flowering comes in July, later than the European lindens, and it is the reason the tree is valued. The flowers are small, pale yellow and strongly fragrant, held in drooping clusters of five to fifteen on a stalk that is fused for half its length to a long, pale green bract, so that the whole inflorescence acts as a single winged unit when it falls. Bees work the flowers heavily for two or three weeks, and the fruit is a small, hard, grey nutlet that ripens in autumn and is dispersed with the bract by wind. The species is native to the Amur basin and the mixed forests of northeastern China, Korea and the Russian Far East, where it grows on deep, moist, well-drained soils in company with Korean pine, Mongolian oak and Manchurian ash.
Science & Biotechnology
The nectar and the honey it produces have been studied closely, because linden honey is one of the most distinctive monofloral honeys of the temperate world. The flowers secrete large volumes of nectar with a high sucrose-to-hexose ratio, and the honey carries a strong, minty, balsamic aroma that comes from a complex of terpenoid and phenolic volatiles, including derivatives of p-menthane and linden ether. Work on the genus has also mapped the sugar composition, the amino acid profile and the pollen content of linden honey, which is used to authenticate origin. The species is an important nectar source in the Russian Far East and northeastern China, and honey from these forests commands a premium.
Tilia is also a genus with a complicated evolutionary history. Molecular work has shown extensive chloroplast capture, where one species carries the chloroplast genome of another as a result of ancient hybridisation, and the Amur linden sits in the middle of that tangle, closely related to Tilia mandshurica and Tilia taquetii and hybridising where their ranges meet. For growers, the practical problem is the seed. It combines a hard, impermeable pericarp with an immature embryo, so it needs both scarification and a long stratification, and germination is spread over two seasons. Work on the species has also examined its bast fibre, which runs in long, strong strands under the bark and was one of the principal cordage materials of the region.
Uses & Benefits
The wood is soft, light, close-grained, easy to carve and remarkably stable, which is why linden is the classic material for spoons, bowls, toys, icons, hat forms and the turned figures that made the craft tradition of central Russia famous. It is also used for drawing boards, for the cores of veneered furniture, and for the internal parts of musical instruments. The bast fibre yields rope, matting and a coarse cloth, and the leaves have been used as fodder and as a tea. Linden flower tea is the standard European remedy for colds, taken hot with honey to bring on a sweat, and the Amur species is used locally in the same way.
In the landscape the tree is planted for shade, for avenues and for honey. It is hardy to at least minus thirty-five degrees, tolerates air pollution and poor urban soil better than most broadleaves, and it transplants well when small. It is also one of the best trees for bees in a cold climate, flowering in the gap between the early summer blossoms and the late summer flow. The one caution worth knowing is that linden nectar is not universally benign: some species, notably the silver linden, have been linked to bumblebee mortality, and the effect varies with the sugar chemistry of the individual tree.
Growing from Seed
The seed needs work before it will germinate. Scarify the hard coat by soaking in concentrated sulphuric acid for twenty to thirty minutes, or by nicking each seed with a file, then rinse thoroughly. Follow with a warm, moist period of two to three months at twenty degrees and a cold period of three months at four degrees. Alternatively, sow fresh seed in autumn in a frame and leave it outdoors for two winters, which is slower but reliable. Expect germination to be spread over several weeks and to be incomplete even in a good batch.
Prick the seedlings out into deep pots, since the root goes down quickly, and grow them on in a cool frame with good light. Plant out in autumn into deep, moist, well-drained soil, in sun or light shade, and stake for the first three years. Keep the ground mulched and clear of grass, and water in the first two dry summers. The tree is slow for its first five years and then accelerates, adding half a metre or more a year. It coppices vigorously, so it can be cut for bast or foliage on a rotation if space is short.
Our Take
A linden is a long-term investment in shade, scent and honey, and the Amur species is the one to choose where winters are severe. Treat the seed properly and the rest is patience.
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