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Iron (Fe) is necessary for the
production of
chlorophyll in plant cells. So, it would
seem reasonable that a deficiency of Fe would result in
a loss of green coloration in the leaf. This yellowing
of the foliage is called chlorosis and it takes on a
characteristic form in Fe deficiency. In such
situations, the main part of the leaf is yellow but the
veins remain a dark green. The newer leaves on the plant
will be affected most.
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Iron deficiency in landscape plants may be present for
one or both of two reasons.
-
Lack of
Iron - In some cases, there is just a low
level of Fe in the soil and this will cause the
deficiency symptoms. In these cases, an application
of an iron compound called iron chelate will reverse
the symptoms.
-
Alkaline
Soil - Sometimes a plant is showing an iron
deficiency but the
soil test says that there is
plenty of Fe in the root zone. This is a situation
involving the availability of the nutrient. Iron is
one of those elements that can only be absorbed into
the root when it is in an acid solution. If the
pH
is too high i.e. alkaline, the root cannot take in
the iron even though it is in the soil.
This is a common problem when growing so-called acid
loving plants such as
Rhododendrons,
pin oak,
boxwood, heaths and heathers,
blueberries and
members of the
Ericaceae Family of plants.
The treatment for this cause of the deficiency is to
lower the pH of the soil in the root zone to about
5.0. This is not a simple process, especially on
established trees and shrubs. Various
sulfur
products may be applied into the root zone of the
plants but these may move very slowly down into the
soil and you cannot work it in since that will
destroy roots. If possible, the best approach is to
either only plant these plants in acid soils or
lower the pH prior to planting them.
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