How to grow strawberries in northern Thailand

Good morning

The first morning of 2011 began nicely, 19°C at 08, a cup of coffee and soft birdsong. I checked the statistics of the Dokmai Dogma blog, summarising that since we began in March 2010, we have had 10800 views, and a 68% increase in viewing frequency in just one month. In December Dokmai Dogma surpassed 2000 views a month. On New Year’s Eve somebody posted two weird links on our blog, and somebody tried to change our password earlier, so we have now changed the password to prevent highjacking. We let WordPress investigate who did that to us.

The origin of the strawberry

The strawberry (Fragaria x ananassa, Rosaceae) is not natural. It is a man-made piece of art, originally composed of a hybrid of the two American wild strawberries  Fragaria chiloensis and F. virginiana. F. chiloensis grows along the American west coast, I have seen it as far north as coastal Oregon. The first strawberry appeared as a mistake, i.e. the two species mentioned above were grown near each other in a botanical garden in Brittany, France, and they spontaneously hybridised around 1740.

Five plants of F. chiloensis had been brought from Chile to Europe already in 1714, after a six months long journey at sea. The French gentleman who loved plants so much was a certain Amédée-François Frézier, whose surname was derived from ‘fraise’, i.e. the French word for wild strawberry. His family had used this name since the 10th century, so him being the accidental father of the strawberry had nothing to do with his name.

Most gardeners in the temperate region have had experience from growing strawberries, and we know it is very easy to propagate them by cloning. Simply detach the baby plants formed on the runners (stolons) and plant them in new areas. To make new varieties, one needs to make new crossings, or look for spontaneous mutants. This is art!

How to grow strawberries in Thailand

Currently strawberries hardly thrive here in the Chiang Mai valley, due to the combination of heat and moisture in the rainy season. At around 1000 meters the climate is much cooler and therefore more suitable. Still, in the tropics the solar intensity is very strong at zenith, so to prevent evaporation one can cover the soil with plastic to suppress weeds and maintain moisture. However, the plastic breaks down into ugly fragments after one season, and the airtight system may make fungi thrive, so then the grower needs to fumigate.

A better organic way is to make raised beds of soil in order to break up the flatness of the surface which lose water more easily. The raised beds should then be covered with Dipterocarpus tuberculatus leaves which has the benefits of the plastic but also allows gas exchange reducing the problem with fungus. A mountain is not only preferred for a cooler climate, but also for the wind which reduces dampness. For watering, the commercial Thai growers do not use sprinklers, as water on the leaves may cause fungal infection. Instead they let a long plastic hose with holes water the roots of each individual plants. This also reduces the need for water and the costs for running pumps.

Many Thai strawberries are quite tasteless. This may be due to premature harvesting, as this is still a fairly new crop. It may also be due to restricted use of tasty cultivars. In the tropics, we can only use day-neutral cultivars, i.e. plants which make flowers and subsequently fruits spontaneously. Many tasty cultivars either need increased or decreased day-lengths (photoperiods) to stimulate the formation of flowers. Research indicate that compost is important for the development of aromas, so a production based on artificial fertilizers might be plain. With proper plant selection I am sure that in the future there will be local Thai cultivars with full-bodied flavours. The western strawberries have had 250 years of improvement efforts.

Eric Danell, Dokmai Garden

Using Dipterocarpus leaves is similar to using straw in the west. In addition to the benefits mentioned above, the fruits do not touch ground where they may rot quickly. One strawberry flower carries many female organs (pistils), and the result from fertilization is an aggregate fruit with many seeds (achenes). The edible part is the enlarged and juicy flowering stem (receptacle). In pineapple and jackfruit, many flowers mature into fruits which fuse with each other, making a multiple fruit.

Raised strawberry beds with irrigation hoses and Dipterocarpus leaves. Growing strawberries in the mountains demands terraces. To prevent erosion Vetiver grass (Chrysopogon (Vetiveria) zizanioides, Poaceae) is planted along the terrace edges (behind the blue parasol).