Peter Cargasacchi: Frost Elementals and Blind Buds.
On the California Central Coast, early Pinot Noir vines began the 2009 bud break near the middle of March. Since then, depending on actual budbreak, we have been dodging and even getting slightly singed by several light frost events in late March and early April, from up and down the coast.
So far there has been little damage, a few singed leaves here and there for the most part. It’s still a little early to tell the full extent, but generally so far so good.
Since last year’s very significantly frost affected season, (the worst frost/freeze in 25 years,) Adam Lee of Siduri Winery, Brian Loring of Loring Wine Company and I have been having a worried discussion as to the effect the 2008 frosts might have on the 2009 crop. We are and have been looking at 2009’s new shoots to project potential fertility by the number of flowers on each new, growing cane as they emerge.
The flowers, tendrils and leaves that are currently growing were actually created last year during the growing season. As many of you know, cell primordia in the nodes (new buds on the previous year’s growing cane from which this year’s canes grow,) differentiate into flowers, tendrils and leaves for the subsequent year, based on heat and light during that previous year’s growing season.
Understanding this phenomena is one of the keys to growing grapes. It requires us to look all the way back to the ancient environment from which grapevines evolved. Fortunately this is fairly easily understood with simple intuition and observation and the understanding that YES! grapevines are vines!!! They evolved in forested conditions, hence the ability to climb trees in order to reach the sunlight…
This influence is visible in viticulture because we know that in vigorous shaded canopies the buds are not very fruitful and there are few flowers. This is because in the evolution of the vine in terms of selection and fitness for the environment, it is not an advantage for the vine to waste energy and reproduce seeds in the shaded environment of the forest floor. There is very little solar energy in the forest shade. This is one of the observations that gave rise to modern vineyard canopy management techniques such as the vertical shoot positioned trellis (VSP) as well as shoot and leaf thinning.
In shaded environments the new cells that are differentiating into future canes are influenced by the shaded conditions. Instead of flowers these cells express genes that produce climbing tendrils which help the vine to climb to the top of the trees. In shaded environments the vines do not waste energy by producing fruit.
Once the vine has reached the top of the forest canopy and sunlight, the cell primordia begin to differentiate more flowers in order to produce future seeds, rather than tendrils, because of the availability of light and energy. This is a great example of basic plant evolution and selection within an environment.
The question Adam, Brian, myself and others have been contemplating is whether the effects of the 2008 frosts has carried over into the 2009 canes. This has been a nagging worry after two previous years of very small amounts of fruit on the vines.
So far we are seeing what appear to be normal amounts of flowers on the emerging canes. In most cases there appear to be two flowers on each cane, and the buds seem to be pushing evenly and uniformly.
It does not appear that there is any carryover effect from last year’s frost events so far. That seems to make sense given that the buds that are pushing now, were developed after the early spring frosts of 2008.
However, there are still some later emerging blocks that had not been harvested last year when we were struck by a early frost in mid October. Some of these blocks that were in the midst of being harvested were struck by frost while still carrying fruit. A secondary mechanism for bud fruitfulness is how much energy the vines carry over into winter. The question here is whether these vines had sufficient carbohydrate reserves stored away for the winter. These vines did not have much of a post harvest opportunity to store carbohydrates. This could affect the size and number of flowers on the 2009 canes.
It is still to early to tell on these late harvested blocks how significant an effect the mid fall frost events had. On the positive side for 2009 fruitfulness, both the 2007 and 2008 vintages were marked by very small crops. Generally after small yields, the vines because of greater energy reserves generally, will tend to have good fruitfulness.
Unfortunately this spring, like last year, we are still in a cold phase (”La Nina” phase) of the ”El Nino-Southern Oscillation.” (This is a Pacific Ocean cycle that largely drives the weather patterns of the West Coast.) Ocean temperatures in the Pacific region are colder than normal during La Nina conditons. Subsequently, there is still a good chance of further frost in 2009.
We are not out of the woods yet…!
