Agriculture Reference
In-Depth Information
that you want to keep. In a vicious cycle, heavy pruning stimulates more vig-
orous, vertical growth.
Fruit color and size.
Overly vigorous, upright fruit trees are slow to come
into bearing and typically bear light crops of large, soft, poorly colored fruit.
There are far greater pest and disease pressures on an excessively vigorous
tree than on a healthy tree exhibiting moderate growth. In such a case, your
approach might be to stop applying nitrogen, bend branches down to form
45- to 90-degree angles with the trunks, and prune as little as possible, but
enough to keep the canopy open and allow light exposure to the trunk and
interior branches.
Leaf color.
Normally, leaves on most fruit trees should be green, exceptions
being ornamental varieties selected for purple or other exotic leaf colors.
Leaves on nitrogen-deficient trees are yellowish or pale green and may be
smaller than normal. Nitrogen is mobile in plants and deficiencies often show
up first in older leaves. Very dark green leaves usually indicate too much ni-
trogen. Sulfur deficiency also causes leaf yellowing, but it is much less com-
mon than nitrogen deficiency.
Potassium-deficient leaves show browning (scorching) around the leaf
margins, with the leaf margins on stone fruits often curling upward.
Magnesium-deficient leaves show yellowing between the veins of older
leaves, forming a herringbone pattern on the leaves. Iron chlorosis shows up
as yellow to white areas between dark green veins and is often associated
with stunted shoot growth. Iron chlorosis is more often due to high soil pH
and/or excessive soil moisture.
Leaf size.
Leaves should be of normal size for that particular variety. Very
large leaves might suggest too much nitrogen and/or shading caused by a
canopy that is too dense. Very small, elongated leaves, especially when they
are clustered at the tips of branches (rosetting) often indicate zinc or copper
