2012 Growing Season Update (Bloom, Petioles, Seasonal Comparisons)

Agriculturally speaking, our vineyard is probably the busiest that it’s been in a long time. We’re in the middle of bloom now, and I just took some petiole samples in for analysis. We’re also just finishing up the first section of our new trellis system for our two year old Pinot Gris and Gamay plants. What does all of this mean? Let me explain…

Bloom, as defied by Wikipedia, means one or more flowers on a flowering plant. While

25 Percent Bloom

25 Percent Bloom

we’ve been doing these vineyard tours, I get a lot of strange looks from people when I mention bloom as a growing stage in our vineyard. Weather you’ve ever been in a vineyard or not, most people are hard pressed to ever remember seeing flowers on a grapevine. I guarantee you they do exist as you can see here. It’s just not a really visually interesting part of the growing season. It is however one of the most important parts, and that is why everyone in the wine industry mentions it. As you can see in the photo here taken today at 25% bloom, the flowers are tiny and white in color. Before you have grapes, you must start with flowers. The unopened flower clusters on a grapevine look like little tiny grape clusters, and that’s why I’m getting some confused looks out in the vineyard.

Pre bloom flower cluster

Pre bloom flower cluster

As you get closer to bloom each flower puckers up with tiny red lines around it. Look closely at this macro view and you can see the flowers puckering up and getting ready to burst. As soon as you can see the tissue covering open, know as the calyptra in flowering plants, the pollen is freed and pollination occurs. Pollination via insects and wind can happen, but vitis vinifera are one of the few flowering plants with both the male stamen and female ovaries. Grapevines can and usually do self pollinate. Cross pollination between species is possible and has happened throughout history. Two of the most popular examples of this in wine history are Cabernet Sauvignon (parent vines are Cabernet Franc and Sauvignon Blanc) and Petit Sirah (parent vines are Syrah and Peloursin). Not every flower on a grapevine will get fertilized. In fact the average is about 30%, and that’s why it’s an important little flower. Low humidity, high temperatures, and water stress can all severely affect a vineyard during bloom. Based on our weather during bloom this year LaVelle Vineayrd, and I suspect most of the Willamette Valley, is looking at a relatively higher percentage this year. As compared to past vintage averages we are about one week behind for bloom on our site this year. However, compared to the 2010 and 2011 vintages, in which we were one month behind, we are more than happy to be one week behind this year.

Bloom lasts a relatively short period of time, and in a week or so we’ll be able to see our

Grapevine shoot, petioles, leaf, and flower cluster

Grapevine shoot, petioles, leaf, and flower cluster

fruitset. With fruitset comes our mid-season checkpoint. There are a few things that we can look at in the coming weeks, but the two most important are:

  1. Taking a look at our macro and micro nutrient levels in the plants
  2. and collecting data on how many fruit clusters we have

we can take a look at the nutrients in the plant by collecting a random sampling of petioles. A Petiole is the stalk of the leaf that attaches the blade to the shoot of the grapevine, as pictured here. By collecting petioles specifically located across from the flower clusters you can send them into the lab and have them analyzed for a nutrient report. There are macro and micro nutrients that grapevines need to produce high quality

Petiole and leaf blade in hand

Petiole and leaf blade in hand

wine grapes.

  • Macronutrients consist of Potassium, Phosphorus, Nitrogen, Magnesium, Calcium, and Sulphur
  • Micronutrients consist of Iron, Zinc, Manganese, Boron, Copper, and Molybdenum

Vines need large quantities of macro nutrients, and the opposite is true of micro nutrient needs. All of the nutrients are important though as they are used for different processes within the vines. By analyzing petioles during bloom we can have the equivalent of a mid-season checkup on our nutrients. You can take soil samples to find out what you have in the soil, but petioles are very important because they let you know what’s getting up into the plant and being used to ripen fruit. Analysis of nutrients varies by vineyard site depending on vigor.

Leaf petiole in hand

Leaf petiole in hand

LaVelle Vineyards is low vigor and therefore we read our numbers on the high side of average. Understanding the vigor of your site and balancing it with the proper plant spacing, rootstock, and nutrients is the key to more fruit concentrated, high quality grapes. It’s almost more art than science though, as debate continues over the subject. In my next installment I’ll go over a current once in a lifetime project now going on in the vineyard, our replanting project.

About Matthew LaVelle

My family and I live in Eugene, Oregon where I own and operate a winery, an estate vineyard, and two tasting rooms (one in Elmira, another in downtown Eugene). I make wine, love food, and spend so much time doing both, that I've decided to write about my experiences here.
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