Lab I. Top Wedge Grafting
text and image version only
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Top Wedge Grafting Flash Card for concise summary of this method.
For information about the use and commercial
applications of Top Wedge Grafting, including links to several Web sites that
describe it in detail, go to Top Wedge Grafting under the List
of Grafting and Budding Methods.
B. Top Wedge Grafting Exercise Check List
- Before beginning this section, you should read over the
Lab Introduction and Overview. Then, review the steps involved in Top Wedge grafting
below, including the videos.
- Is your knife very sharp? Remember, a dull knife is
more dangerous than a sharp one, when it comes to grafting. If you need instruction
on knife sharpening go to Lab Introduction and Overview .
- Potted hibiscus plants
- Grafting knife
- Budding rubbers
- Twist ties
- Small plastic bag
- Water spray bottle
1. Rootstock preparation.
- Choose a hibiscus stock plant with an actively
growing shoot tip, that is at least 0.5 cm, but
preferably less than
1.0 cm in diameter at the point at
which you will cut off the top section and insert a new scion. This graft
can be placed at any height along the stem, from approximately ten cm from
the top to ten cm from the base. If you are planning to insert one or more
T-buds and/or Chip buds on the same plant, the Top Wedge Graft should be placed
up towards the top of the main shoot, at least 25 or 30 cm from the base.
2. Cutting the stock plant
- Using pruning shears or grafting knife, remove
larger leaves and flowers from the portion of the shoot where you plan to
place the scion.
- Make a horizontal, clean cut with your pruning
shears, removing at least the top 4 - 6 cm of the shoot, so that the stem
diameter across this cut is at least 5 mm (approx 1/4 inch).
- With a sharp grafting knife, split the understock
vertically, down the
center, from the horizontal cut to
a point approx. 3 - 4 cm down the stem. Depending on the hardness of the wood,
a gentle rocking motion of the knife may be useful to start the downward cut.
- In Uganda, Passion fruit is top wedge grafted
to a fusarium resistant rootstock. The top of the rootstock is removed with
a horizontal cut. Note minimal stock plant diameter, approx. 0.5 cm.
3. Cutting the scion
- Scion selection: It is possible
to cut the scion from the top of the scion donor plant where the shoot is
still green or only partially woody, so that the scion growing point will
be the actively growing shoot
tip from the scion donor plant. Alternatively,
the scion many be cut from
a lower, woodier section of the
shoot where new growth from the scion will arise from a more or less dormant
lateral bud. The former is preferable, since an actively growing terminal
scion is more likely to form a successful graft union and new growth from
the scion begins sooner. However, the latter may be necessary if a terminal
scion is not available from your scion donor plant.
- Cut the scion from the scion donor plant with
pruning shears or a sharp grafting knife, in the same way that the top of
the stock plant was removed. The scion should be at least 3 cm long to as
much as 6 cm long, and include as few as one node in the case of a non terminal
scion, or as many as several closely spaced nodes, in the case of the preferred
teminal scion. A scion longer than about 6 cm
is more likely to be dislodged (knocked over)
later on, and it has a greater surface area for desiccation.
- Trim off any leaves from the scion, except
very small ones (<1 cm long) at the growing shoot tip.
- Cut the base of the scion into a "V" shape
by making two straight tapering cuts about 2
to 3 cm long. A single long cut on each side is preferable to making several
passes with the knife to trim the "V", since the former is more likely to
be straight and even. The diameter of the scion should be approximately the
same as that of the upper, cut end of the stock.
Note: If you are not using the top portion of
the stock plant which you just removed as the scion for a different stock plant,
it is good to use it to practice making the "V" cut, before proceeding to the
- Insert the scion into
the split upper end of the stock plant by sliding the tapered ("V") tip of the scion
downwards with gentle pressure, until the top of the "V" cut is even with
the top, horizontal surface of the stock. If both are equal in diameter, the
vascular cambia of the scion should be aligned with that of stock, but if
the scion is slightly smaller in diameter than the stock, the scion should
be placed to one side of the stock (rather than centered), as for cleft grafting,
so that the cambia align at least on one side.
4. Tying and covering the graft
The scion and understock are first tied firmly
in place with a budding rubber to create pressure between the cut surfaces.
This is followed by wrapping the union with Parafilm to further prevent desiccation,
and finally the entire scion and upper portion of the stock junction is covered
with a plastic bag "tent" to create a humid environment as a third barrier to
water loss from the scion.
- The budding rubber
is wrapped tightly around the graft, from the
base upwards, about 1 cm below the graft union, by holding one end of the
rubber band against the stock with the thumb of the left hand while wrapping
with the right hand. If the scion tends to "pop out" as you tie from the base
upwards, try tying from top downwards, to trap the scion in place. To secure
the end of the rubber band, the first turn with the right hand should cross
over this end, "trapping" the end under the first turn. The band should be stretched
as it is wrapped around the stem to create
pressure. Terminate the wrapping about 1 cm above the horizontal top cut of
the stock by pulling out a "loop" with the right hand and tucking the
end of the rubber band through this loop before releasing it and trapping
it in place.
- Cut a piece of Parafilm
about 2 inches wide and 3 inches long. The
paper backing is divided into 2 inch sections, so cut it along that line.
Remove the paper backing, and fold this 2 x 3 inch piece in half long ways
so it measures about 1 x 3 inches. To adhere firmly, the Parafilm should be
stretched slightly before it is wrapped in place. Hold one end of the Parafilm
just below the bottom end of the budding rubber wrapping, and wrap upwards,
just as you did with the budding rubber, until the rubber is entirely covered.
Remember to stretch the Parafilm as you wrap. At the upper end, fix the Parafilm
in place so it will not unwrap by running your thumbnail across it, which
tends to stick it to the layer of Parafilm below it.
- Create a humidity tent
over the graft by placing a small plastic bag upside down over the scion and
upper portion of the stock and tie it firmly with a twist tie near the bottom
(open end) of the bag, approx. 2 cm below the graft union. Before placing
the bag you may wish to lightly spray water inside the bag, with the
- Top wedge grafting is occasionally practiced
in breeding of fruit tree rootstocks. In this case, top wedge grafting is
being used to bulk up a rootstock selection (the scions shown here) which
is available in limited quantity. Shoots of the rootstock genotype grown from
these scions will be layered to get them on their own roots, and then lined
out in the field to establish a stool bed for propagation of the rootstock
genotype in greater quantities. In this case the top wedge grafted plants
are placed in a fog chamber to minimize
desiccation, rather than covering each with a plastic tent.
5. Post budding management of the Top
Wedge grafted plant
- Place the grafted hibiscus under shade in
the greenhouse for several weeks. It is especially important to keep your
grafted plant out of the sun since the plastic "tent," that maintains
a high humidity around the scion, can over-heat very rapidly and kill the
- Active growth of the scion after one to several
weeks is a good sign that the graft is "taking" properly.
- After about 3 weeks cut one or two slits,
about one inch long, anywhere in the bag so that the humidity will be gradually
reduced and the scion will become acclimated to the lower ambient humidity.
- One week later, remove the bag entirely.
- At this point you should inspect the graft
union for signs of callusing by removing the Parafilm and budding rubber temporarily.
A healthy graft union will exhibit a thin line of whitish callus all along
the exposed edge of the stock scion junction. At this point, you should tie
the stock and scion back together, for several more weeks, before their final