Lew, I'll put up my hand as a tea agronomist amongst other things.

The subject of tea quality and stress is, as you suspect, not
straightforward. Neither is it with people some of whom thrive on it
while it destroys others - and react in different ways to any
particular type of stress. I left the safety of corporate Unilever
after 27 years because that sort of stress (lack of control over my own
decisions) gave me psoriasis. The stress of running my own, often
financially precarious, business has never affected me - in fact it is
often exhilerating. My initial Teacraft business partner couldn't
handle the financial insecurity and quit after a few years. Different
plants do well in different soils.

My observations with tea are that quality and stress is not a straight
line correlation. It's certain that too much of a good thing -
nitrogen, warmth, abundant water, will stimulate fast vigorous growth
that lacks quality - Rains teas in Assam and Darjeeling is a good
example - soft cups but high yields. Slow growth - due to cool weather
or drying winds combined with rocky soil tends to give a peak of
quality - the low yielding Uva quality season in Sri Lanka for
instance. Just to take one single variable - nitrogen fertilizer - one
certainly show a diminishing cup quality with increasing nitrogen BUT
the line will not start at zero. The response is quadratic. Reduce
nitrogen below a certain point and cup quality will again diminish.

I suspect the effect of rocky soils is the same - a degree of depletion
slows growth and improves quality - but deplete too far and it will
reduce quality.

Soil pH is possible the most obvious illustration of the effect. Tea
thrives at pH 5.0 but growth declines with increasing soil pH until
plants actually die at pH 7.0 Similarly, growth declines at reducing
pH and plants actually die at pH 3.0 Between 3 and 7 there is a
perfect quadratic response peaking at 5.0 I supect that the best pH
for cup quality is around pH 4 - below optimum for yield (pH 5) but
well above the plunge into the death zone.

The moral being that for optimum tea quality you must not spoil the
bushes with unlimited treats - deal with them firmly but not too hard -
lots think that effective child raising follows similar rules.

Nigel at Teacraft




Lewis Perin wrote:
> You've hit on a very interesting point. Probably none of us, except
> Nigel, could convincingly pose as an agronomist, but I do know that
> this isn't as simple as it seems. Sure, tea plants subjected to
> environmental stresses, e.g. poor nutrition, will yield less leaf, but
> for high quality, there are cases where we demand that the trees or
> shrubs be tortured:
>