By Mercy Olmstead, University of Florida and
Markus Keller, Washington State University
Chip Budding for Grapes
Chip bud grafting is a convenient method for changing varieties or
top-working grapevines in a vineyard. This may be conducted to allow
growers to change the cultivar to meet increased consumer demand, adapt
to changing market conditions, and garner increased economic gains.
Chip bud grafting is a form of field grafting, conducted on vines
already planted in a vineyard.
This is different from bench grafting,
which is conducted on dormant plant materials (Table 1; Figure 1).
Table 1. Different grafting techniques used in producing grapevines
with a rootstock.
Figure 1. Omega bench grafting of grapevines
Grafting combines two plant portions--the scion and rootstock (Figure
2). The graft union is covered with grafting tape to protect the new
graft union and ensure that the scion and rootstock have enough contact
to form callus. Callus is formed during the grafting process that
connects the two plant parts, creating one cohesive stem with
continuous transport tissues (xylem and phloem). Xylem and phloem are
differentiated within the graft union from callus cells.
Figure 2. Grafting brings two different parts
of a vine (scion and rootstock) together
Scion Wood Preparation
Top-working a vineyard requires advanced planning of at least one year.
Scion wood should be collected when dormant in late fall (November) or
early winter (December) to ensure there is optimum carbohydrate storage
in the wood for viability of the wood for future grafting and growth.
Collect scion wood from healthy grapevines known to be "clean" (free of
virus--preferably tested to be virus-free) and avoid grapevines that
show symptoms of disease or insect damage. Selection of scion budwood
should be pencil-thick in diameter (9/16-inch to 3/8-inch), straight,
uniformly round, and well-lignified (Figure 3). The internode length
should be approximately 2.5 inches to avoid selecting wood that grew
too vigorously or weak, and can serve as an indicator of wood
carbohydrates and/or bud viability. Cuttings of scion wood should
include four to five buds for a total of 12 to 16 inches to facilitate
Figure 3. Scion wood bundled for storage
after collection in late autumn
Once collected, scion wood can be bundled with 50 to 100
cuttings/bundle and treated to reduce the incidence of certain pests
and diseases while in storage (e.g., pathogenic fungi, crown gall
bacteria and certain phytoplasmas). This can be done by placing the
wood in a water bath at 122ºF (50ºC) for 30 minutes.
After the heat treatment, rinse the wood in cool water to prevent
tissue damage. Heat treatments can damage grapevine buds if scion wood
is collected late (early spring); therefore, it is important that scion
wood is collected in the late fall. If hot water treatments are not
possible, fungicidal drenches/dips can be used, such as hydrogen
peroxide type products (ZeroTol).
Preparing Grapevines for Chip Budding
Grapevines should be prepared for chip budding during the normal time
period of dormant pruning by cutting back the existing grapevine trunk
to encourage the growth of suckers. In the spring, the strongest two
suckers should be trained up to the cordon wire and attached with
string or vinyl tape. These will become the new rootstock for the new
As the suckers grow, disbud all but the top two leaves to provide
transpiration for the new shoot (Figure 4). This will allow water and
nutrients to flow up the shoot and through the new graft union after
budding. Prevent any additional lateral growth from buds on the sucker,
as these will only serve to draw carbohydrates away from the new shoot
Figure 4. Leave two leaves on the top of each sucker when
preparing vine for chip budding to provide transpiration.
Chip Budding Process
Preparation of the bud: To begin the chip budding process, scion wood
can be removed from cold storage and unwrapped from bundles. Soak the
scion wood for one to two days to rehydrate the tissue. Chip buds
should be made with two cuts with the initial cut being made with the
knife perpendicular to the wood surface, approximately 1/8-inch (1 mm)
from the base of the bud. The second cut should be made with the knife
placed approximately 1/4-inch (3 mm) above the cut, drawing the knife
smoothly to the first cut around the back of the bud (Figure 5). Be
sure to cut buds on the day of grafting or just before grafting
in-field to avoid dehydration. Cut buds cannot be stored, so cut only
enough buds for the grafting activities for that day.
Figure 5. Cutting buds from scion wood the day of grafting,
and cut buds (inset).
Preparation of the Rootstock: To prepare the trained sucker in the
field, make cuts in the sucker to mirror chip buds previously cut from
scion wood. Chip buds are most successful if the diameter of the chip
bud and the recipient stock are matched carefully. Insert the chip buds
onto the new rootstock, and wrap tightly with grafting tape to ensure a
tight connection. Buds must have a tight connection to form callus and
strongly develop the graft union. White or transparent grafting tape
will help to reflect solar radiation.
The location of the graft union is very important in areas that are
prone to fall and spring frosts. Graft unions made lower to the ground
where radiation freezes are common are prone to failure, compared to
those made higher on the rootstock. Chip buds that are placed higher on
the rootstock are also much easier to train to the cordon wire than
those placed lower.
New growth should emerge from the newly grafted bud approximately one
to two weeks after budding (Figure 6). Growth from the existing
rootstock will tend to grow more quickly than that from the new bud, so
remove this growth quickly to encourage growth of the new scion. Keep
the two existing leaves on the rootstock until there is 6 inches (~15
cm) of new scion growth. At this point, the existing rootstock can be
removed to about 1 inch (2.5 cm) above the graft union.
Caring for the Grafted Vines
Newly grafted grapevines should be cared for in the same manner as
newly planted vines. Irrigate, fertilize, and control weeds as
appropriate for a young vineyard in your region. With the removal of a
large portion of the canopy, the much larger root system can cause
vigorous canopy growth for the first two years. Buds that break from
the rootstock should be removed to direct growth to the scion.
Encourage hardening off in the autumn by slowly reducing irrigation and
fertilization, as this new graft union is particularly sensitive to
Figure 6. A successful graft union three weeks
after chip budding
Encourage growth to develop the new training system. To prevent vine
stress, remove any crop that sets the year after grafting. In the
second year after grafting, a small crop can be harvested, and full
crop potential can be achieved in the third year.
Advantages and Disadvantages of Chip Budding Grapevines
|Ability to change cultivars to meet market demands without removal and
replanting of vineyard blocks.|
Ability to return to original cultivar, particularly in areas where
varieties can be grown own-rooted.
Easier and faster than other methods of field grafting.
Significant yield can be realized in third year, compared to fifth year in complete vineyard replanting.
|Requires experienced grafting crews for best results.|
Graft success can be variable, depending upon experience of grafting
Chip bud grafting during summer months requires adequate storage of
scion wood until use.
Chip Bud Grafting in Washington State Vineyards, Washington State
University pdf 4 pages
1 Olmstead, Mercy and Keller, Markus.
"Chip Budding." extension.org.
University of Florida and Washington State University. 30 apr. 2014.
Web. 23 May 2014.
Fig. 1,2,3,4,5,6 Olmstead, Mercy. Chip Budding. 2014.
University of Florida. extension.org.
Web. 23 May 2014.
Published 23 May 2014 LR