Lithocarpus polystachyus Seeds | Many-spiked Tanoak

Young reddish flush and leathery green leaves of many-spiked tanoak — Many-Spiked Tanoak (*Lithocarpus polystachyus*): Fagaceae, warm hill forests of southern China.

LATIN NAME: Lithocarpus polystachyus

COMMON NAME: Many-Spiked Tanoak

Plant Profile

Many-spiked tanoak is an evergreen oak relative of twenty metres whose young leaves are the reason it is grown: they are intensely sweet, and a handful dried makes a pale golden tea with no sugar at all. The tree has leathery, glossy leaves, dense clusters of small catkins in summer, and small acorns that ripen brown in the second autumn. It is a tree of the warm hills of southern China, and it is as much a crop as an ornamental in its home country. The crown is dense and low-branching, and old trees are often cut back to a stump and allowed to resprout for picking.

Science & Biotechnology

The sweetness comes from dihydrochalcone glycosides, principally trilobatin and phlorizin, compounds that are hundreds of times sweeter than sucrose and are not metabolised as sugar, which has made the leaves a subject in natural-sweetener research. The species produces these compounds in the young flush only, so the harvest is a spring event. It sits in Lithocarpus, the stone oaks, a genus of several hundred species in Fagaceae that is being reshaped by molecular work, and its relationships are still unsettled. Trials in Guangxi have measured both the sweetness yield and the regrowth of coppiced bushes, since the two are in tension. Leaf harvest trials show that coppiced bushes produce a sweeter flush than tall trees, which is why the tea gardens are kept low.

Uses & Benefits

The leaves are dried and sold as sweet tea, tian cha, in Guangxi, Hunan and Guizhou, where it is drunk as a cooling beverage and used in folk medicine for coughs and as a mild anti-diabetic. The wood is hard and used for fuel and small construction. In the garden it is a handsome evergreen shade tree, slower and denser than a true oak, and it can be kept as a large hedge. It is not a substitute for sugar in cooking, since the sweetness carries a liquorice-like aftertaste, and the tea is better drunk weak than strong. The wood also makes good charcoal, which is the other reason the tree is kept.

Growing from Seed

Sow fresh acorns in autumn, two centimetres deep, and leave the pots outside through winter; they lose viability if they dry. Germination is in early spring and can be uneven. Grow the seedling in light shade for its first year and full sun thereafter, in a deep, acid to neutral soil. It is slow to establish and then steady. If the leaves are wanted for tea, pick the young flush in April and dry it in shade, and prune after picking to keep the crown low and the shoots coming. Do not feed it nitrogen, since that softens the flush and reduces the sweetness.

Our Take

A tree that makes sweet tea from its spring leaves, and one of the more useful evergreens a warm garden can hold. Pick the flush, not the old leaves, and the sweetness is all there.

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