The Crush - December 2019 - 2

[ FEATURE STORY ]
grafted large acreages for Central Valley and Coastal growers,
and also works in the Pacific Northwest and throughout the
U.S. Rodriguez suggested growers consider phenological
characteristics when choosing a new variety in relation to site
and vine vigor, and seasonal development (early, mid or late
season timing) to be compatible with site conditions.
While economic factors differ for each grower and site, Komar
believes top-working is a good decision if the grower can get
five or more years of production and sales with the new variety.
Grafting services can cost from $2 to $4 per vine depending on
volume, vineyard access and other factors. Top-working can
be successful in vineyards of any age, but is more common in
vineyards from about 5 to 20 years old. It is possible with larger
diameter vine trunks and with head-trained vines. Experienced
grafting crews achieve successful take rates ranging from 90 to 98
percent of the vines grafted.
When a grower contacts him about grafting service, Rodriguez
said, "We talk about vineyard access, desired varieties, soil
types and site conditions. We will do a site inspection to identify
possible issues in the field." He added, "The grower needs to
understand possible risks, have a good source of clean budwood,
and may want to do virus and disease testing. If the grower
is hesitant to convert the whole vineyard, they may want to
experiment with a couple rows and do more acreage later."
Budwood orders should be placed with nurseries early to obtain
desired variety and clonal selections and sufficient quantities.
"Let the nursery know the material is for field grafting and the
approximate age and diameter of the vines to be grafted," Komar
said. Since nurseries often collect dormant budwood for their
own bench grafts, not all buds are suitable for field grafting.
Komar suggests over ordering by 50 percent to have enough
useable buds.
Winter pruning in advance of grafting should include removal of
all vine material from trellis wires. If an old cordon is wrapped
around a trellis wire, it may be necessary to remove and replace
the wire. In some cases, changing varieties could also be a
good time to change the trellis and canopy structure to better
mechanize management. New stakes and trellis wires should be
installed prior to grafting to be ready for vine training.
GRAFTING AND POST-GRAFTING MANAGEMENT
Grafting timing and success is temperature related. Early spring
grafting is scheduled for warmer locations first, then progresses
to cooler sites later. The final trunk cut is commonly one to two
weeks prior to grafting. Depending on soil moisture and vine
water uptake, the trunk may need to "bleed" before grafting
to prevent saturation of the graft union and allow proper
callousing.

2 / DECEMBER 2019

Photo courtesy of Top-Notch Grafting

Graft types include T-budding (or chip budding) using a
dormant, mature bud, as well as whip grafting and cleft grafting.
Rodriguez said the graft type choice can be based on the time
of the season, the size of the vine, and grower preference. The
graft union is wrapped with a protective (non-sticky) stretch tape
and/or painted with Tree Seal.
Successful graft take can be over 90 percent, but a follow-up
pass is commonly done in late June or July (or sometimes the
following season) for vines that don't take. Extra budwood
should be kept in cold storage for follow-up work.
Komar cautioned, "Grafting may not be something to undertake
if the grower has serious labor issues." Suckers grow from
trunks, and three to four suckering passes may be needed. Once
grafted buds callous, vine growth can start in two weeks to one
month and can be rapid. Retraining and vine tying onto the
trellis requires hand labor. Vines can grow at different rates, and
a crew may have to go through the vineyard weekly. "If you
don't take care of the vines after grafting and train them properly,
you won't get good results," Komar said.
A GROWER'S PERSPECTIVE
In 30 years at Ridge Vineyards, David Gates, senior vice
president of vineyard operations, has overseen field grafting
at estate vineyards in the Santa Cruz Mountains and Sonoma
County. Variety changeovers have included riesling to cabernet
sauvignon, merlot to cabernet sauvignon, merlot to chardonnay,
zinfandel to carignane, and syrah to petite sirah.
His most important advice: "If you hire a professional grafting
crew, do exactly what they tell you to do in preparing the
vineyard and managing it after grafting. They know what's
necessary for a successful graft take." Gates prefers T-budding
and has had good success with it. "Make sure the vineyard is
healthy. The healthier the vine, the better the take."
Gates said, "Pay close attention to the vines and shoots after they
start growing. They can be delicate and are susceptible to wind
damage, so make sure they are tied up properly."
The Crush - December 2019

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