Re: What effects does tea have on plants?

Irrigating plants with coffee, tea, soda, and other human beverages is a 
popular science fair project but the results are usually not easy to explain 
because there are many possible effects. If plant growth is reduced compared to 
a control it could be due to a toxic chemical, high salinity (low osomotic 
potential), or unfavorable pH. A boost in growth is most likely due to the 
mineral nutrient content of the beverage or maybe the pH. Tea is made from 
leaves, which contain mineral nutrients required by plants.

Tea contains high levels of fluoride, which can be toxic to plants. Fluorine is 
not an essential element for plants. In monocots with long, narrow leaves, such 
as the houseplant spider plant, the flouride is carried in the xylem with the 
transpiration stream and accumulates at the leaf tips. The leaf tips die as a 
result. A flouride level of 0.25 mg/liter is enough to damage the most 
sensitive species. One mg/liter is a typical level in drinking water to prevent 
tooth decay.

You might be able to obtain a nutritional analysis for tea from the 
manufacturer or find one in the literature which would give you a clue. The Tea 
FAQ website mentions that green tea contains human-nutritionally significant 
levels of magnesium, potassium and manganese, all of which are essential to 
plants.

Reference

Hershey, D.R. 1993. Evaluation of irrigation water quality. American Biology 
Teacher. 55:228-232.


Tea FAQ