Blog 137: How Do Light, Heat and Water Content Affect Tea Plants?

The heathy growth of tea plants requires a set of conditions. In an ideal growing environment, tea plants can grow stronger, live longer, delivery better quality fresh leaves, and have a higher production output.

A common tea plant growing environment requires appropriate conditions of light, heat, water content, air quality, landform, and soil quality. Today, let’s discuss how light, heat, and water content affect tea plants. This blog will offer you a set of numbers and facts to help you better understand what makes a better tea mountain field.

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I. Light

Typical tea plants have a preference for sunlight and a good tolerance of sunless environments. Tea plants’ photosynthesis has a relatively low light saturation point and a high light compensation point.

The photosynthesis of tea plants strengthens when illumination intensity increases. When illumination intensity exceeds over 50,000lx, tea plant photosynthesis normally does not increase.

Too much or too little sunlight can be detrimental to tea plants. (click for more photos)

The illumination intensity is closely related to tea plant’s unit output and the quality of fresh leaves. When the intensity of light decreases a little, nitrogen compounds in small leaves increase and carbon compounds (such as tea polyphenols, reduced sugar) decrease. These changes enhance the taste of freshness and briskness of tea leaves.

The length of illumination time also greatly affects the growth of tea plants. It directly influences the flowering period. Depending on the illumination time, tea plants’ flowering period can be early, delayed, or nonexistent. The length of illumination time also plays a vital role in tea plants’ dormancy.

Visible light is the core of tea plant photosynthesis and organic matter generation. Chlorophyll A and B can absorb blue light, purple light, red light and orange light. Solar radiations that can be absorbed by chlorophylls are called physiological radiations. Under red and orange lights, tea plants can grow and develop at a faster pace.

Although infrared ray can not be directly absorbed by chlorophylls, it can deliver heat to soil, water, air, and tea plants. As a result, the infrared ray can boost seed germination and shoot growth.

Heat is essential in tea-making, and it's also crucial to tea field management. (click for more photos)

II. Heat

To all tea plants, there’re 3 basis temperatures: optimum temperature, lowest temperature, and highest temperature. Different cultivars at different growth stages have different basis temperatures.

When new tea leaves just sprout, most tea cultivars grow in an average temperature of 10℃/50℉. The optimum temperature for tea plant growth is between 20℃/68℉ to 30℃/86℉. When temperature goes over 35℃/95℉, the growth of new leaves stops or significantly slows down.

There’s always a limit to a tea plant’s temperature tolerance. When the growing environment exceeds this limitation, it’ll cause harm to tea plants. A temperature that is either too high or too low is detrimental to the health of tea plants.

There’re 2 categories of low temperature damages. Damages above the freezing point is called “cold damage”, and below the freezing point is called “frozen damage”. Tea plants’ tolerance varies depending on the cultivar, the age, the tea field maintenance, and the season etc.

In winter, tea plants can survive in very low temperatures. (click for more photos)

Commonly, the lowest temperature tea plants can withstand is between -10℃/4℉ to -5℃/23℉. But when tea plants are covered by snow, they can also withstand a low temperature of -15℃/5℉.

However, during the spring growth of tea plants, if a frostbite hits the tea field and the temperature suddenly drops to 1℃/34℉ to 2℃/36℉, new sprouts could be frozen to death. This is also one of the worst case scenario we face in spring.

Spring leaves, however, are afraid of sudden temperature drops. (click for more photos)

Of course, a high temperature will also cause damage to our tea plants. When the monthly average temperature rises above 30℃/86℉ and the highest temperature exceeds 40℃/104℉, tea plants could suffer from “heatstrokes”. Luckily, this rarely happens in our tea mountain fields.

III. Water Content

Water is vital in all organisms. Tea plants generally have a water content between 45% to 80% (young leaves and buds: 75%-80%, older leaves: 65%, branches: 45%-50%, roots: 50%).

Water is also the raw material for photosynthesis and the vehicle for nutrients transportation. The level of water content helps regulate a tea plant’s body temperature to prevent overheating.

Tea fields require a lot water to supply the demand of tea plants. (click for more photos)

A normal tea plant requires tea fields with precipitation between 1000mm/39in to 1300mm/51in. A mature tea fields has a daily water consumption of 1.3mm/0.05in in winter, 4mm/0.18in in spring, and 6mm/0.24in in summer. The water consumption moves positively with average temperature.

Only few places in the world can produce high quality tea leaves. (click for more photos)

The best quality tea requires the optimum growing environment. In the real world, there are only a handful locations that can meet all requirements. We hope this blog can help you better understand why the same tea plant behaves differently when they’re moved, as well as why tea cannot just be produced everywhere.

We hope you enjoyed today’s blog. As always, if you have questions or suggestions, please leave a comment, tweet us @valleybrooktea or email the author directly at zhang@valleybrooktea.com. Please also follow us on Instagram @valleybrooktea and join our mail list to get our daily tea updates and our latest promotions!

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