Spring arrived a week or so ago, and much of the country has finally seen flowers start to bloom and things start to green up. I have kept track of spring in California, as vineyards in many areas saw early an early warm spell, which actually caused an early bud break for some white varietals in Napa Valley. This was followed by cold spells that had vineyard managers seeing sleepless nights as they monitored for frost. Then they got rain and clouds, that turned early spring breakers away from the coast. Now the warm temps are back and bud break has begun in many areas.
Now I am seeing beautiful photos on my Instagram feed of vineyards carpeted in green, dotted with flowers and the dormant vines spouting plumps ends, that are starting to open and leaf out. So it seems appropriate to dive into a little of what happens in spring in the vineyards.
Perfect spring conditions have the weather warming gradually. The barren vines become dotted with bright green buds. Bud break when the tiny buds of green burst forward with those vividly bright green leaves. The vines coming back to life after being dormant all winter is a time for celebration right?
Sadly, with spring comes spring frosts, and those are a nightmare for those who work in the vineyards.
Frost & frost protection
If you have ever driven by a citrus grove in winter, you might see the big barrels for fire (smudge pots) and fans to spread around the warm air. This can be used in vineyards also.
Large fans or wind machines are used in vineyards to move the air around. This directs the warmer air from above down toward the vines and displaces the colder air on the ground away from the vines. You need one of these machines for every 10 to 12 acres of vineyard.
Heaters or smudge pots can be used to heat the air in the vineyards. These heaters typically burn about a gallon of diesel oil per hour and give off a thick warm smoke that the vineyard fans then circulate to keep the vines from freezing. Mind you, this is not just about the heat from the smudge pots, it is also about the smoke, particulates, carbon dioxide and water vapor. This “smog” is a layer blocking out infrared light which prevents radiant cooling. This method requires about 25 smudge pots per acre, which are typically at the edges of the vineyard.
Now most vineyards now also have an overhead sprinkler system. When it gets to freezing a fine mist is turned on, it coats the buds and keeps them from freezing. Here’s the magic of this, as the water changes to ice, it releases a small amount of heat and that is what protects the vines. Of course this depends on the water continuing to flow and continuing to freeze and give off this latent heat. Of course this leaves you at the mercy of the amount of water in a vineyard. During times of drought this kind of frost protection becomes difficult.
Vineyards will also mow down the cover crops to allow for airflow down off of hillsides and into valleys. This protects the hillside vines. Also they do not till or cultivate the soil, because that would let out the heat in the soil.
What kind of damage can frost do?
It can completely wipe out the buds on a vine. Vines can re-sprout, they will do this if the primary buds are destroyed. The problem with this is that when your pruned, you set up for where the vine would sprout and the secondary sprouts may not be so conveniently located. It also will severely diminish the amount of grapes for harvest.
This is why many vineyard managers and winemakers spend endless sleepless nights in the spring worrying about frost. Nights are spent tracking temperature patterns hourly and if the temperature drops getting out there and turning on that frost protection equipment and hoping for the best. Okay…enough of the scary part…on to bud break.
This is the opening of the buds left behind by pruning. These fuzzy beady little things have all the stuff to grow leaves, shoots, tendrils and berries.
About a month after bud bread the flowers come out. These are tight bunches of tiny flowers, and each flower has the potential to become a grape.
Standby for more scary stuff. Wind and frost can wipe out the flowers and that would mean that those bunches of grapes would never form. There is the possibility of a re-sprout, but at this point in the vines season the yield will be considerably smaller.
This is when the flowers start to take the shape of grapes in the cluster. As the are pollinated the flowers drop their petals and tiny green sphere emerge.
Now things are warming up and we are moving into summer. When things really get rolling in the vineyard!
You can check out our pages on the seasons in the vineyard at “the seasons”