On 23 Nov 2004 it was written:

Theo,

The answer is not simple. However... I do not grow tropicals, only temperate
climate hardy plants in zone 6.5 If one uses a soiless mix (e.g. 80% Turface
or similar), Micronutrients are important although more so for some species
than others. Micro nutrients are not essential throughout the year. Bonsai
use different things at different times of their annual cycle. I use a
commercial product called Micromax once per year, in the early spring just as
the buds are opening. 1/2 level teaspoon per gallon of soil in the pot gives
near miraculous results in the color, quality, and substance of leaves on the
bonsai. My observation is taht the trace elements provided are most needed
when the new leaves are forming but are of very limited use after the leaves
have hardened off. At that point regular fertilizers seem to have enough stuff
in them to keep the juices flowing properly. Regular use of micro
nutrientscould actually be toxic to some plants.



Oh my. I must disagree here. I must. With everything except
the first sentence, which is true: The answer is not simple.

The chemical life of plants also is not simple and cannot be
simplified in one or several brief e-mails -- at least not by me
in MY limited understanding.

But plants grow ALL year -- even when we say they're dormant
they grow a little -- somewhere. And as they do, they use the
nutrients they find in the soil to help them grow. Most native
soils are well-enough stocked with macro- and micro-nutrients
that trees and shrubs almost never need fertilizing, despite the
claims of the home-garden-oriented fertilizer manufacturers!

Bonsai soil on the other hand, is deficient in nutrients --
almost sterile in many cases. And bonsai soil drains so quickly
that any chemicals we add are quickly leached away by our
frequent watering. This is why we fertilize at weekly or twice-
weekly intervals -- to replace the nutrients that the soil lacks
and loses.

So bonsai need regular feeding to thrive -- both in macro- and
micronutrients. They need NPK, & S generally to grow roots,
stems and leaves (not necessarily in that order ;-). The
micronutrients (Fe, Mn, Zn, Cu, B, S (tho it usually is
considered a macronutrient), and Mo take care of the minutiae of
plant life. And they do it all year long!

Try withholding iron (Fe, a micronutrient) from a bonsai at
any time of year and you will almost immediately begin seeing
signs of chlorosis (grow azaleas in alkaline conditions, which
prevent uptake of Fe, and see how pale the leaves immediately
become). Ditto Manganese, Mn. Lack of other micronutrients
affects things you don't see as easily, such things as the
thickness of cell walls, the production of enzymes and hormones,
and a host of other vital processes in plants.

But who am I to argue with "the way it's been done." However,
_I_ won't give my plants a jolt of micronutrients once or twice
a year; they get them in small doses every time I feed (or
*almost* every time, I use fish emulsion sometimes and it lacks
many/most? micronutrients) -- which is throughout the year, but
less frequently in winter.

But as they say: Different strokes.

Jim Lewis - - Tallahassee, FL - Nature
encourages no looseness, pardons no errors. Ralph Waldo Emerson

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