the ability to quite accurately predict when bloom
will occur for grapevines. This work is based on the
accumulation of degree-days from bud break to bloom.
The time of bud break depends on the grape growing
area, the specific variety and rootstock.
The number of accumulated degree-days from bud
break to reach bloom is variety dependent. For
Thompson Seedless, 650 to 700 degree-days are
required. For most wine grape varieties, 500 to 600
degree-days are needed.
For the areas listed above, we have recorded the
dates of bud break for this season for a "typical vineyard".
The predictions of peak bloom time are based on actual temperatures to date then normal temperatures
until the degree-day total is reached for each variety
listed in each area. Bloom projections are updated weekly.
