Apples and pears
Recently I got a question about the pear-like (apple-like?) fruits you see in Thai markets, what they are and whether or not they can be grown here in the Chiang Mai valley in northern Thailand.
To the right is an ordinary apple (Malus x domestica, Rosaceae) and to the left is ‘Asian pear’ or ‘nashi pear’ or ‘apple pear’ or ‘sand pear’ or ‘Chinese pear’ just to name a few English vernacular names (Pyrus pyrifolia, Rosaceae). ‘Nashi’ means ‘pear’ in Japanese. The Thai name for this species is ‘sali’. The Chinese pear prefers a wet climate, and is native to central and southern China. Smitinand treats it as a species exotic to Thailand.
Like with citruses, all wild pear ‘species’ can hybridize and so it is a matter of definition what you call a species. The wild pear we know from northern Europe is Pyrus communis. However, the pear genus contains many species in temperate Eurasia. Flora of China treats fourteen native species including Pyrus pyrifolia, and estimates the worldwide number to be 25. At least one Yunnanese species is also known from the Thai highlands (Pyrus pashia). Pyrus laosensis is reported from Laos and might be found in Thailand, but is now treated as an apple (Malus doumeri) which is also found in China. This ‘apple’ has been used in crosses to make new pear cultivars. The ordinary apple (Malus x domestica) and European pear (Pyrus communis) have the same chromosome number and can be crossed too (6th Rosaceus genomics conference 30th September-4th October 2012), so even the distinction between apples (Malus) and pears (Pyrus) seem artificial and similar to the Citrus/Fortunella dilemma.
Originally, in Linnaeus Species Plantarum from 1753, apple was Pyrus malus and pear was Pyrus communis. The Latin word ‘pyrus’ means ‘pear tree’ and ‘malus’ means ‘apple’. The Latin word for pear fruit is ‘pirum’. To make things more complicated, some consider Linnaeus’ Pyrus malus to be modern Malus pumila (paradise apple), not ordinary apple (Malus x domestica). Claiming that Linnaeus did not know plain apple may seem outrageous, but even so he probably gave a scientific name to a ‘hybrid’ since the common apple contains genes of Asian Malus sieversii and European Malus sylvestris. On the other hand, if they all hybridize, one might argue that all apples are local adaptations or cultivars of Pyrus malus.
Leaving the tricky nomenclature we may want to explore if it is possible to cultivate Chinese pear here in Thailand? At high elevation the climate may offer cold shocks to trigger flowering and subsequent fruit formation. It seems unlikely though that today’s Chinese and Japanese cultivars would survive the six month’s long dry season of the Chiang Mai valley. Even if they did, temperatures may not be sufficient to trigger flowering since Chiang Mai minimum temperatures during the cold season in December-January rarely go below +10°C and afternoon temperatures often reach 30-32°C (warmer than Swedish summer). From our experience here at Dokmai Garden other temperate Asian species such as ginkgo, wasabi, wisteria, paulownia and ginseng will not or just barely survive, while Thai highland cherry (Prunus cerasioides) grows but it does not bloom.
Ongoing hybridizations and selections may eventually result in man-made pears flowering in a hot and dry climate. Since pears and apples generally demand cross-pollination of different varieties (individuals) to make fruits, you actually need to develop two cultivars flowering simultaneously.
Being unable to grow pear in the Chiang Mai valley does not make me sad. I am perfectly happy with the multitude of other delicious fruits you can grow here.
The sliced Chinese pear in the foreground oxidizes (turns brown) more slowly than the apple slices seen in the background. The grainy structure of the Chinese pear is due to the gritty sclerenchymatic cells embedded in the flesh, a characteristic of the entire pear genus and used to separate it from the apple genus.
Since there are thousands of man-made cultivars of apples and pears, preference is highly subjective. I believe the cultivar of Chinese pear (Pyrus pyraster) shown here, which is commonly sold in Chiang Mai, has a weak flavour compared to many aromatic European pears (Pyrus communis). Still, its crispy and gritty texture and watery content is most refreshing on a hot day. Future crosses between the Chinese pear and the European pear, spiced with genes of lesser known wild ‘species’, may take flavours and textures to new levels (papples).
Text & Photo: Eric Danell