Weather, Soil and Climate for growing teas

Background

Climate / weather and the soil are considered as main factors for the growth of tea plants. All Tea types are coming from the same plant species namely, Camellia sinensis. This special plant is currently grown in all 7 continents in the world and produces various types of teas. While the processing or the manufacturing of the leaves is what decides what kind of tea leaves will turn into Black, Green, White, Oolong, etc., the growing region also plays a big role in the sensory profile of the tea. 

Terroir 

Soil, altitude, rainfall, and climate are collectively named as ‘terroir’ in tea cultivation. Terroir is the main reason why you can have many different sips of the same tea type which taste clearly different. That determines the sensory profile of the tea. Terroir explains various environmental factors which contribute to the sensory profile of tea. This term was first used by French winemakers and derived from the French word “Terre” meaning land. Later on this term has been adopted into other industries like tea, coffee, cheese, and chocolate etc. Now let’s look at some key terroir factors affecting the growth of tea.

Climate 

The main factor which affects the tea taste is the climate. Tea bushes can only be grown in places with warmer and humid climates. In sub-tropical or temperate regions, tea flushes start to emerge from the spring and the bush provides few flushes until mid-autumn. If there isn’t a variation in weather conditions, the made tea will taste too light and flat. Climatic variations are important for the development of complex tasting notes which make each tea unique. Because, due to climatic stress secondary metabolites are released inside leaves, and those metabolites create unique and unmatchable sensory characters.

Temperature: The average annual temperature for the perfect growth of tea bushes is in the range of 60 – 75°F. Tea bushes should ideally have a total annual temperature of 6,300 – 7,200°F. Temperatures which are higher or lower compared to above affect the accumulation of tannins (Polyphenols) in tea. When the temperature exceeds 95°F, the process of tannin accumulation is halted. If the temperature is higher than 95°F continuously for a prolonged time period, it will result in burning tea flushes.

At the same time, when the temperature is too low, that will change in the physiological and chemical composition of tea flushes. This badly affects the bush growth and the quality of tea flushes. Tea grown at high temperatures has lower levels of the compounds like caffeine, L-theanine, polyphenols etc. than at lower temperatures. 

When the temperature is low, the made tea is lower in strength, but the flavor and aroma is much better. When the temperature is at the higher side, shoot growth is faster, so more active compounds are synthesized inside the leaf. As a result, tea is stronger and has a rich cup color. 

Rainfall: The average total annual rainfall for optimal tea bush growth is about 59 inches and the rainfall should be evenly distributed throughout the year. The minimum annual rainfall for tea should be 39 inches, monthly 2 inches. This is the ideal condition for better tea flush growth. The average monthly rainfall during the tea-growing period (First 2 years after planting) should be higher than or equal to 4 inch. If it’s less than 4 inch, the tea plant will not grow properly.

Humidity: Tea plants need high air humidity during growth period. The ideal air humidity is around 85%. Higher humidity, heavy dew and morning fog are ideal for the growth of tea flushes. Humidity lower than 70% will affect the growth and ultimately the tea yield in a great deal.

Elevation / Altitude 

Elevation or altitude plays a key role in deciding the sensory profile of tea. That is because higher elevations are exposed to higher UV radiation amounts, and more dramatic changes in temperature, which forces the synthesis of secondary metabolic compounds in tea. For instance, high grown Ceylon Dimbula or Indian Nilgiri tea is grown in the hills, almost 6,500 feet above the sea level.  These high grown teas have got flavors which are said to be more subtle and refined thanks to colder temperatures and slow growth rate of the tea bush.

On the other hand, in Ceylon Ruhuna or Indian Assam, tea grows below 2,000 ft above sea level. But you need to keep in mind that low grown teas are not lower in quality. These low elevational regions have the tropical climate, sufficient rainfall, and rich, fertile soil, that provides the tea brisk and denser flavor profile. 

Soil 

The soil which tea is cultivated in can differ dramatically and depends on the bedrock beneath the land. The soil mineral content is reflected in the tea, and minerality in tea is a characteristic which is sought after. The soil nutrients are also absorbed directly by the tea bush through the roots, therefore bushes grown in nutrient-rich soils generally produce healthier tea flushes. 

Tea bush is grown well in sandy and acidic soil with a pH between 5.5 and 6.5. If your soil doesn’t make that pH, planters / farmers add pine needles or sulfur to make it more acidic. The soil for tea should be well drained, fertile and tea bushes should have sufficient space to spread apart by at least three feet. The depth of the soil is also important for better growth of tea. The soil depth from the growing surface to the bedrock should ideally at least be one and half meters or more. Shallow soil limits the root growth. Tea bushes cultivated in shallow soil are more susceptible for droughts and extreme conditions. Tea soils should not be too sandy or too clayey. Sandy loam to silty loam soils are ideal for the growth of tea. 

Latitude 

The latitude (distance from the equator) decides the number of flushes emerge in a year. Teas grown close to the equator can be harvested throughout the year because the weather is very consistent. Tea grown in sub-tropical and temperate regions can go through a dormant period specially during the winter. This results in a lot of secondary metabolites. The teas which are produced soon after the dormant period in early spring are called first flush teas and can be the most coveted and most priced teas in the world!