Agriculture Reference
In-Depth Information
Heading.
This involves cutting a stem between branching points and is often
done on 1-year-old wood just above a strong bud. Heading shortens and
stiffens the limbs. It eliminates apical dominance for a time and usually
causes a strong growth response at buds several inches below the cut. Apical
dominance is caused by hormone-like chemicals produced in the tip of a
trunk leader or shoot and results in straight, unbranched growth. The more
wood that is cut off, the greater is the growth response. You normally see
less regrowth when horizontal limbs are cut than when upright branches or
shoots are headed. Stiff branches are desirable for many training systems,
especially for freestanding trees. If the branches become too stiff, however,
they can become more susceptible to breaking due to heavy crop and snow
loads.
Hedging is a type of heading cut that is sometimes used for fruit trees,
grapes, and berries. Beginning in the late 1900s, hedging became a popular
means of reducing labor costs in commercial orchards and vineyards.
Tractor-mounted, sickle bar-type implements were used to cut the sides and
tops of trees and vines to remove unwanted vegetative growth and main-
tain desired shapes. Hedging cuts are indiscriminate, however, and typically
produce a thin layer of densely branched, twiggy growth immediately be-
low the cuts, leaving a barren, woody interior. This dense outer layer can re-
duce the amount of light that penetrates to the center of an individual plant
or canopy, and orchard hedging should be followed up with more detailed
hand pruning. Hedging can be used with newer, high-density training sys-
tems, but it requires a substantial amount of skill and careful follow-up cor-
rective pruning.
Thinning.
In this type of pruning, cuts are made at the junctions of branches.
These cuts result in less growth than with heading, and in a stronger, more
natural structure. Thinning is important for selecting scaffold limbs and
keeping a plant open, which allows light to penetrate throughout the canopy
and ensures healthy and fruitful growth on the lower and internal parts of a
plant.
