Agriculture Reference
In-Depth Information
on to an established rootstock in the nursery row so as to obtain a
mm
interstock. The first graft may be made some weeks before the second. An even
simpler way is double shield budding. A small budless shield of the interstock
cultivar is slipped into the T-cut on the rootstock and a bud of the upper scion
cultivar put on the upper and outer cut surface of the budless shield and both
are slid home (Garner,
-
,
).
Effects of temperature on grafting
and budding
The temperatures used in controlled conditions, e.g. in bench grafting, and
the choice of season for budding and grafting in the nursery or orchard reflect
the temperature requirements for three separate processes.
Bark-lifting (slipping): this is a requirement for those grafting and bud-
ding techniques in which scion material is inserted under bark which is
parted from the wood. This is the case in crown grafting (rind graft-
ing) in which pieces of scion graftwood with long sloping cut surfaces
are pushed down between the rind and the wood around the perimeter
of the decapitated trunk of a tree which it is desired to 'top-work' to a
new cultivar. It is also the case for T-budding in which a scion bud is
added to a complete rootstock stem by sliding it under the bark through
an incision. In England the bark does not readily part from the wood
until April and the best time for T-budding is from the end of June to
mid-August.
Callus growth and union formation: the complete range of temperatures
permitting the formation of callus from apple scion and rootstock cuttings
and grafts was found by Shippy (
◦
C and
◦
C. At
) to lie between
◦
C only a small amount of callus developed over several months and
between
-
◦
C the rate of callus formation increased with rise in
temperature. At temperatures above
◦
C and
◦
C injury usually resulted and at
◦
C death of tissues occurred within a few days. In general, temperatures
below
◦
C are most satisfactory. Depending on temperature, apple grafts
may therefore be callused over a period of several months or within a few
days. As a consequence, even when there is no need for bark-lifting, as
in chip budding where a piece of rootstock tissue including outer bark,
phloem, cambium and some xylem is removed and a similar shaped piece
of scion stem carrying a bud substituted, temperatures have to be high
enough for active rootstock growth. In England this is from April to early
September (Howard,
). Under subtropical conditions in Turkey, chip
