Upon further research, A phosphorus deficiency some times causes
a "purpling" of young shoots and leaf veins. According to the source,
the problem is not usually a lack of Phosphorus in the soil b/ a lack
of nitrogen that limits the uptake of the element. A lack of nitrogen
will definatley cause a lack of vigor in the plant.
There is also a condition called "Red Cane" and is the result of
over cropping.





--- In ampelography@y..., "Jeff Jernegan" <jeff@j...> wrote:
> Does anyone know what nutritional deficiency might cause a generally
> vigorous variety (Madeline Angevine growing on its own roots) to be
less
> vigorous than MA vines in other vineyards, set irregularly
(different size
> berries, many small), and have petioles, young stems and young
leaves that
> are substantially red? Other vines of different varieties in
adjacent rows
> 10' away show no effect or devigoration. Pinot Noir is on one side,
> Siegerebbe on the other. All the vines are 10-15 years old and
have had no
> fertilization or other supplements in the past decade. The soil is
deep
> sandy loam with some tendency to be short in magnesium and possibly
boron.
> Other younger MA vines grown in other vineyards, or even planted
recently a
> few hundred feet away show none of the weak growth, reddish color
on the
> petioles & stems. I'm fairly certain we are not looking at any
disease
> here, rather some shortage in nutrients.
>
>
>
> ------------------------
> Jeff Jernegan
> ------------------------
> Maury Island Vineyards
> Puget Sound, WA
>
> jeff@j...