Tea trees grow over long periods of time in certain special natural environments. Ecological factors influence and constrain the course of a tea tree's life and, thus, give rise to the optimum growing conditions of tea, including: sunlight, temperature, humidity, climate, soil, and vegetation cover. The growth and development of a tea tree is entirely dependent on how well these external conditions are satisfied. When environmental factors are satisfied, tea trees are able to exhibit optimal growth. Consequently, selection of tea tree material is greatly influenced by the factors affecting tea leaf quality. The ecological conditions of the tea growing area are decisively important in determining whether the tea leaves are good or bad. By exploring climate, soil, vegetation, and topography, we learn that historical tribute tea, traditional famous teas, and even today's high-grade teas virtually all come from high mountain growing areas.
Tea was conceived under moist and rainy conditions in primeval rain forests of southwest China's border regions; consequently, tea trees have evolved over time to favor moist, humid conditions. However, differences in the elevation, soil, climate, and ecology in which tea is grown give some tea advantages and others disadvantages.
1. Temperature: Tea trees love warmth and grow best at temperatures between 20 and 30C. Higher environmental temperatures may be beneficial to tea tree growth, but such temperatures do not produce tea of ideal quality. For instance, tea trees in tropical regions exhibit exuberant growth and have high yield, but the resulting tea is of low quality. Although its aroma is strong, it lacks purity. If the temperature can be reduced to a certain limit (approximately 10C), although tea tree growth is comparatively slower, the quality of the tea leaves is higher. Environmental temperature roughly follows changes in elevation, and temperature affects the vitality of the tea, thereby influencing the transformation and accumulation of chemical substances in the tea leaves. Consequently, tea leaves from trees growing at different altitudes differ in terms of quality. For example, tea polyphenols and catechins are found at lower concentration as the growing elevation increases, while amino acid concentration increases as the elevation increases. This provides the chemical foundation for the refreshing, sweet, and mellow flavor of tea. In addition, the aromatic substances in tea leaves increase at higher elevations. These fragrant substances undergo complex chemical transformations during the tea production process to produce different types of fragrance.
2. Rainfall: Tea trees are moisture loving plants of the tropics and subtropics, which require approximately 100mm of rainfall per month. Generally speaking, rainfall amounts increase at higher altitudes. When growing conditions provide ample moisture, photosynthesis contributes to difficulty in condensing sugar compounds, and cellulose is not easily formed. This can cause fresh leaves to maintain their tenderness and avoid becoming coarse. Abundant rainfall also promotes nitrogen metabolism, which increases the total nitrogen content and amino acid levels in the fresh tea leaves. These factors are beneficial to the flavor of the tea.
3. Sunlight: The duration of sunlight exposure is directly related to temperature and moisture. As the amount sunlight increases, the temperature rises and the level of evaporation from the tea leaf surface increases. Exposure to ultraviolet radiation is also greater. To protect themselves, young tea leaves must produce large quantities of anthocyanins and anthoxanthins. Levels of tea polyphenol also increase correspondingly, and, finally, cellulose content increases, which results in tough and coarse tea leaves. The sunlight that we perceive is composed of different parts of the solar spectrum, including high frequency, microwave, ultraviolet, visible, and infrared light. The visible spectrum is the main source of illumination for creating organic material in tea trees through photosynthesis. According to a survey of solar radiation patterns and variation conducted by the Yunnan Provincial Tea Institute and Yunnan Astronomical Observatory, Chinese Academy of Science, higher altitudes not only receive higher total solar radiation but also receive abundant quantities of blue and violet light, which assists tea trees in nitrogen metabolism. At moderate elevations, on the other hand, red and yellow light is relatively abundant, which benefits the carbon metabolism and the formation of tea polyphenols and contributes to rapid tea tree growth. Of this light, infrared is not directly absorbed by the chlorophyll of the trees but is a source of heat in the soil and thus provides essential temperature preconditions for tree growth. Ultraviolet light, with its relatively short wavelength, serves to suppress tea tree growth; however, relatively high levels of nitrogen compounds are found in the leaves of tea trees bathed in ultraviolet light, which benefits the formation of fragrant substances in the tea.
High mountain tea growing areas lie among dense forests with frequent clouds and mist. Tea trees grow in the shade of surrounding trees. In such conditions, the tea trees enjoy relatively high amounts of diffused light. This often allows the trees to develop with fine quality. In particular, it increases levels of nitrogen compounds in the tea, which is extremely advantageous in improving the quality of the tea.
A comparison of the soil of high mountain tea plantations with that of low-lying (Taidi) tea plantations shows significantly different levels of physical composition (soil particles) and chemical composition (soil fertility). In general high mountain tea plantations are found in mountainous areas with more severe climates. Thousands of years of exposure results in relatively complete weathering of the soil. Gravel is abundant and soil permeability is high. These areas often have reddish brown or yellowish brown soil. In addition, vegetation in such mountainous growing areas is allowed to run its natural course, and the biological content of the soil is high with a complete food chain in place. The soil contains abundant organic substances, various minerals and rare elements, and high levels of fertility. All of these factors contribute to healthy and strong tea tree growth. Low lying tea plantations, on the other hand, largely contain red soil. The weathering of the soil is relatively incomplete with weak soil composition and low levels of organic and biological material. As a result, tea tree growth is often relatively poor, and the aroma and flavor of the tea is far beneath that of high mountain tea.
Comparing the amount of vegetation of low-lying tea plantations and high mountain tea growing areas, we see that high mountain tea growing areas are characterized by flourishing vegetation. This provides moderate regulation of sunlight, which is beneficial in producing diffuse light and increasing the quality of the tea leaves. In addition, the high degree of vegetation cover regulates the humidity in the air, and thereby improves humidity conditions and soil fertility.
In comparing high-mountain and low-lying tea plantations, another factor that influences tea quality is topography. High mountain tea growing areas are dominated by towering mountains. Exposed rocks receive strong sunlight. Mechanical disintegration and denudation effects are strong, leaving behind large amounts of residual soil. As a result, the mountain top soil layer is thick and frequently composed of acidic reddish brown or yellowish brown soil. Mountain tea growing areas are dominated by precipitous topography with good drainage characteristics. If an advantageous orientation can be selected, it is also possible to avoid cold wind and ensure moderate air temperature. Consequently, tea plantation topography can affect the chemical composition of the tea leaves. As a result, high mountain and plantation teas have different characteristics, as follows:
High mountain tea - Tea leaves: robust and strong, long leaf sections, green color, and abundant fine hair; processed tea: tightly tied strips, large and fleshy, visible white fuzz, strong fragrance, and intense flavor.
Plantation tea - Tea leaves: small leaves and buds, firm and thin leaf bottoms, open and flat leaves, and yellowish color; processed tea: thin and small strips of tea, light body, slightly weaker aroma, and ordinary flavor.
Based on the above comparison of high-mountain and plantation tea, we can see that mountain tea is somewhat superior. Mountain tea growing areas produce quality tea due to the influence of the tea tree growing ecology, which encompasses climactic conditions, soil factors, plantation cover, and topographical conditions. Such growing conditions allow for stable tea tree development and higher overall quality. Due to these factors, high mountain tea plantations have supported flourishing tea tree growth over the past several thousand years even without artificial fertilization.
Because tea trees are restricted by the ecological conditions of their growing environment, a tea tree's development and the composition of its fresh leaves differ under different growing conditions. Good fresh tea leaves are an essential prerequisite for good quality tea. We now understand that tea leaf quality is absolutely related to its natural environment as well as climactic factors. Besides these factors, tea leaf quality is also closely tied to tea tree variety, cultivation method, ecological conditions, agricultural technology, and harvesting methods employed. In particular, the quality and quantity of tea grown on a lowland tea plantation is inseparably linked to fertilization, pruning, breeding, and cultivation methods as well as the growing density. In the discussion below, let's consider these factors to further understand the differences between human-cultivated plantation bush tea and naturally growing high mountain large tree tea.
Tea tree varieties:
Plantation tea is mainly comprised of artificially bred improved tea varieties. To preserve the integrity of the tea varieties, plantation tea is primarily cultivated through asexual reproduction. The scope of tea tree variation is relatively minor, with the leaf quality of a tea tree closely resembling that of its parent. However, such trees have relatively weak resistance, and insecticides must be applied each year to ensure the trees are able to resist diseases and pests. Light dosage of insecticides is insufficient, while heavy application may cause issues related to pesticide residue. This results in a difficult balancing act. High mountain big tree tea, on the other hand, is generally made up of local community varieties with substantial variability within a breed and relatively strong resistance. The trees grow scattered within the forest, making application of insecticides difficult. As a result, insecticides are almost never applied to these tea trees and there is no need to worry about pesticide residue.
In low-lying tea plantations, a certain number of tea trees per square meter are planted. Because a given amount of soil is only able to provide limited nourishment, the tea trees within a small area fiercely compete for nutrients. Plantation tea trees grown through asexual reproduction contain no main roots, but instead consist of only lateral roots with relatively shallow root systems. Even though older plantation tea trees grown through sexual reproduction contain primary roots, the growth of the trees is artificially stunted to prevent them from becoming too tall. The extent of a tree's root system is directly proportional to the growth of its crown, and thus they too possess limited root systems. Shallow roots prevent the trees from absorbing the nutrients of deeper layers of soil. In theory, it is therefore always necessary to supply plantation tea trees with fertilizer to ensure they receive ample nutrients. Tree fertilizer can generally be categorized as organic and inorganic fertilizer. Ordinary tea. plantations primarily rely on inorganic fertilizers. These are mostly ammonium nitrate fertilizers. If used long term in large quantities, such fertilizer can cause the soil to harden and lose its physical properties. This results in widespread deterioration of the soil quality of the tea plantation. Its ability to supply essential nutrients to the tea trees gradually decreases, thereby reducing the quality of the tea.
Organic tea plantations, on the other hand, rely on organic fertilizer. Use of natural organic fertilizer can reduce the amount of coarse fiber in a tea tree's new growth and thereby delay the maturing and hardening of new leaf tips, which increases the tenderness of the tea leaves. Although organic fertilizer can increase the quality of tea leaves, it is slower to take effect. Most of the nitrogen stored in tea trees takes the form of arginine in the tree trunk, but the growth process follows the maturing of new buds and amino acid requirements arise accordingly. This inability to provide sufficient nutrients where they are needed is a common shortcoming of nitrous fertilizer.
Unlike plantation tea trees, high mountain large tea trees generally have several square meters of land per tree. They have a guaranteed supply of nutrients and grow relatively tall. They possess correspondingly deep root systems, which are able to fully absorb the nutrients provided by various layers of soil. In addition, the organic food chain of the soil is relatively complete, which allows it to supply the various factors needed for growth as well as necessary rare elements. Because the natural environment is able to provide ample and balanced nutrients, there is no need to apply fertilizer.
Low-lying tea plantations have virtually no call plant growth to provide the tea trees with shade, which causes the trees to be exposed to direct §un-light. Although this increases production, the intense sunlight causes rapid leaf growth and can lead to coarse and tough leaves with high cellulose content. It has a very negative effect on tea quality. In addition, when young tea leaves arc exposed to intense ultraviolet radiation, they are forced to produce large amounts of anthoxanthins and anthocyanins to protect their ability to develop normally (high levels of anthocyanins results on so-called purple buds). Large quantities of tea polyphenol compounds are also produced, which gives the tea a rough and astringent flavor. Large tree tea, on the other hand, grows within forests surrounded by many larger trees, which give the tea trees shade and allow them to receive diffuse sunlight. Growing in these shaded conditions, the amino acids and fragrant substances in the tea leaves greatly increase. In addition, the leaves maintain their tenderness longer, contain lower cellulose contents, and do not suffer from excessive levels of tea polyphenols. The various substances in the fresh tea leaves are both abundant and balanced. The tea is mellow and thick with reduced bitterness and astringency.
Plantation tea is pruned to counter the apical dominance of the tea trees and thereby allow the side branches to fully develop. This expands the area that can be picked to increase production. Pruning also controls tea tree height to facilitate tea harvesting. However, the nutrients that can be stored by a tea tree are limited. When the germination ratio suddenly increases, the nutrients originally supporting the growth of a single bud now need to support the growth of multiple buds, which naturally results in lower quality tea leaves. In comparison, mountain large tree tea grows naturally and is picked rather than clipped. The apical dominance is pronounced and nutrient supply is ample. The fresh tea leaves are naturally thick and strong and of high quality.
Selection and breeding of improved varieties is primarily carried out in order to increase production and increase economic productivity. An important index of increased production is the rate of germination. Thus the rate of germination of improved variety plantation tea is much higher than that of local variety large tree tea. Chemicals are also applied to accelerate germination of plantation tea trees. As a result, the germination period of plantation tea trees is long, while the resting period is brief. This deprives the trees of suitable time to accumulate theine. The tea leaves appear plump and thick, but have weak substance. If tea trees do not have reasonable time to recover, tree growth and future tea quality will be greatly affected. Although high mountain large tree tea trees produce small volumes of tea, they have short germination periods and long resting periods. New growth benefits from a relatively long time to accumulate nutrients, which results in tender tea leaves with abundant internal substances.
Based on all of the factors described above, we see that lowland plantation tea is characterized by its high yield and close planting. Its advantages are its high production volumes. Although it falls short of perfect tea quality, plantation tea provides economic benefits and is easy to manage and harvest. It offers strong appeal in the commodity economy of the general market. High mountain large tree tea, on the other hand, is produced in relatively small units, but its appeal lies in the natural ecology, lack of chemicals, and organic status. Its advantage over plantation tea is primarily due to its superior quality, and today this large tree tea is widely praised by tea experts and industry.
Development of large tree tea requires a certain level of protection and care. Although agricultural advancements have increased tea production and quality with varying degrees of success, these benefits are accompanied by corresponding disadvantages. In particular, if these methods are blindly applied when the disadvantages are not fully understood, the drawbacks outweigh the benefits. In certain cases, practices with well-known disadvantages such over-harvesting, blindly stimulating production, or applying chemicals in violation of a ban are carried out in pursuit of short-term benefits. These short-sighted acts not only lower the quality of the resulting tea products, but also gravely harm the natural environment. So looking forward, addressing the question of how to promote ethical tea growing and strengthen agricultural education is key. We can establish a tea market with proper understanding of tea production techniques and carry forth the fine traditional culture of Puerh tea.