How Climate & Geography influence Tea
Even if the first country to discover and grow tea was China around 5000 years ago, today the tea plant is grown in over 60 countries and manufactured on nearly every continent on Earth. The total regions under cultivation continues to grow and there is an expected increase in consumption mainly due to its medicinal use benefits.
The tea plant is highly adaptable to a wide range of growing conditions and its inherent resilience to the environment in which it is grown is part of tea’s appeal. Variations in climate and geography are some of the most important natural elements that affect flavour and other qualities of tea, creating unique properties and an extensive variety of teas. Specific climatic influences are expressed in the tea and this is referred to as terroir.
Generally, tea grows in tropical and subtropical regions. The ideal temperature varies between 18 – 28 degrees, which means that it requires cool to warm temperatures with at least 5 hours of sunlight per day. Even so, tea plants can handle light snow or frost, but not prolonged cold winters or heavy frost.
In addition, seasonal precipitation is relevant in influencing the characteristics of tea. Plenty of rain (1500 – 2500 mm per year) and a high relative humidity of 75% - 85% leads to development of abundant foliage and well established roots. Most of the well-known tea producing regions have defined seasonal climates, such as Sri Lanka and Kenya.
Moderate fluctuations in climate help to develop particular flavours. The stresses caused by a rise or drop in temperature or a short period without rain, stimulate a chemical reaction in the plant in order to retain chlorophyll, concentrating particular flavours. In spite of this, tea does not tolerate drought nor withstand stagnant water. This is the reason why most commercially managed tea operations are located on hill slopes in the highlands, where drainage is adequate.
Soil has a strong influence on tea flavour and quality. Tea compounds differ considerably depending on regional soil type and management. Soil needs to support the roots and provide appropriate levels of nutrients, minerals and moisture required to support the tea plant.
The most important feature is soil pH, which should be within the range of 4.5-5.6. At this acidic pH level, the absorption of nutrients is balanced. The optimum soil moisture is between 70% - 90%. Moreover, well-aerated soil with more than 2% organic matter contributes to a healthy soil, as a result, healthy plants able to defend themselves from pests and diseases.
The latitude of a tea plantation controls the amount of sunlight a plant receives every day. In equatorial areas such as Kenya, sunlight is a constant 12 hours a day, meaning tea can be produced almost all year round. As the distance from the equator increases, the amount and strength of daily sunlight starts to vary considerably, according to the time of the year.
A scientific research published by the Polish Society of Horticultural Science points out that “Tea can be grown in a wide range of climatic conditions and soils from Mediterranean to warm, humid tropics, from countries such as Russia in the northern latitudes to Argentina and Australia in the southern latitudes.” Hajiboland, R. (2017). (1).
Many of the plantations producing the best tea are found at high altitude. Despite this, it is not easy to grow tea at high elevations. As elevation increases, crop yields reduce because temperatures are colder, the soil is rockier, and rainwater flows increase downhill, reducing the available water for plants at the top. Thus, it can be challenging to grow tea plants at all in these conditions.
The elevation of the plant impacts almost every phase of its growing process, from flavour development to pest control. At high altitudes, colder temperatures naturally protect tea plants from insects. This does not only reduce the need for pesticides but also it reduces the bitterness in the leaf. Overall, high mountain teas are recognized as having more complexity to the flavour, less bitterness, and a creamier texture to the finish such as Taiwanese Oolongs. Moreover, organic practices are not only preferred, but necessary, as fast-growing fertilized plants do not develop a strong enough root system to withstand the cold winters and regular soil erosion.
At heights above 1000 metres, days may start with mist followed by changing sunlight levels due to varying cloud cover and cool air, and then cold nights. This creates stress to the plant which is beneficial to the flavour. As an example of how altitude affects flavour is Sri Lanka. The black Ceylon tea grown there is divided into categories:
- Low grown (up to 600 metres): used for tea bags
- Mid grown (600 – 1200 metres): excellent strength for strong loose leaf
- High grown (1200 – 1800 metres): most delicate aromatic black teas
Finally, the rocky soil and natural drainage reduce the amount of water in the leaves, leading to concentrated and intensified flavour compounds.
A remarkable advantage of mountainous regions is that as they are located in rural areas, pollution from industrialized regions is far enough to keep tea fresh and contaminant-free. These rural villages still operate much the same as they have for centuries.
Owing to the multiple growing conditions that a tea plant can adapt itself to, it is worth mentioning that not all teas can be adapted to any climate or geographical circumstance. And every small fluctuation in the environment can positively or negatively affect the final product. Therefore, even if farming methods continue operating as usual for every tea plantation, there is the expectation of increased variability in tea quality year on year due to today’s unpredictable weather.
Regarding geography, high-grown teas often have many desirable characteristics which contribute to a better tea and sometimes reach a higher price than lower-altitude teas. However, this does not mean elevation is the best or only determinant of quality for all teas. There are several variables to analyse when considering tea quality.
- Hajiboland, R. (29/02/2017) “Environmental and nutritional requirements for tea cultivation”. Folia Horticulturae.