𝘊𝘢𝘴𝘵𝘢𝘯𝘦𝘢 𝘮𝘰𝘭𝘭𝘪𝘴𝘴𝘪𝘮𝘢 Blume is a plant belonging to the Fagaceae family, known to have adult trees reaching up to 18 m, which is a medium-size for trees. If you want to recognise it, have a look for a tree with relatively low branches and with long, pointed, wavy-edged leaves. Better to look for leaves during the summer or early autumn seasons as the tree is deciduous, meaning it is losing its leaves during the bad season (winter). No worries if you missed it this year, as you’ll have plenty of time to look for those as individuals can live up to 150 years, although their lifespan varies. This chestnut species is native to mainland China, Taiwan, and the Korean Peninsula, where it can be found in forests and mountains up to 2740 m . Humans also plant and grow Chinese chestnuts, for their appearance and shade as well as for the consumption of their delicious nuts, which they start producing 3 to 4 years after planting.
Chinese chestnuts prefer moist, well-drained, gravelly and mildly acidic soil with a pH of 5.5 to 6.5 under full sun; but they are quite hardy and can survive periods of drought, cold and even frost. They are also resistant to chestnut blight, a fungal disease which manifests as orange bark cankers (lesions) caused by 𝘊𝘳𝘺𝘱𝘩𝘰𝘯𝘦𝘤𝘵𝘳𝘪𝘢 𝘱𝘢𝘳𝘢𝘴𝘪𝘵𝘪𝘤𝘢. This disease provokes the death of up to 4 billion American chestnuts (𝘊𝘢𝘴𝘵𝘢𝘯𝘦𝘢 𝘥𝘦𝘯𝘵𝘢𝘵𝘢) when it spread from East Asia in the first half of the 20th century . In Europe, the impact of this spread on the European chestnut (𝘊𝘢𝘴𝘵𝘢𝘯𝘦𝘢 𝘴𝘢𝘵𝘪𝘷𝘢), although still significant, was much less devastating than that seen in America, as the European species was protected by a hypovirus, a strain of virus that infects the fungus and therefore defends the tree from its full damage. The Chinese chestnut, as it evolved alongside the fungal parasite to begin with, is less susceptible to its damage, but it can still carry the disease and spread their fungal spores, including to other tree species such as oaks and maples .
Chinese chestnut trees blossom in summer between May and August. They are monoecious, which means both female and male reproductive organs are present on the same plant. The flowers don’t look much like flowers: they are called “catkins”, which are long, cylindrical hanging spikes covered in tiny flowers and are mainly wind-pollinated. A few tiny female flowers are located at the base of each catkin while the rest is constituted of male flowers. For efficient pollination, however, individuals must be cross-pollinated - meaning that each plant cannot reproduce with itself but instead that one tree’s female flowers must receive pollen from another tree.
After successful pollination, chestnut kernels develop inside burrs, which are the thick, spiny coatings (ouch!) that protect them. These grow for 12-14 weeks and then, when they are ripe, fall onto the ground, between September and November. The spiny burrs protect the chestnuts from curious predators. Other than being very tasty, chestnuts also have lots of nutrients and vitamins, and their consumption can provide us with many health benefits, including antioxidant, antimicrobial, anti-inflammatory, anticancer, hypolipidemic, hypoglycemic and neuroprotective effects. Even the shell, the thin layer of skin stuck onto the nut ( don’t eat the burr!) has important nutrients. For animals, chestnuts are an important source of energy during the fall and winter seasons, allowing them to better survive in approaching cold weather. Moreover, dried chestnut leaves can be used as bedding for livestock during winter.
You can try to find Chinese chestnuts in Hong Kong (it is the right season to see the fruits drop!), but at the Hong Kong Biodiversity Museum you are sure to see a nice spiky burr and kernel up close.
Text: Alan Tsoi
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