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Winter Blog 2017
Grapevine response to cold weather:
I am often asked how grapevines respond to winter weather. Especially given the crazy weather we’ve had the last couple of winters. In summer, it’s obvious if vines are stressed from drought or nutrient deficiencies. But in winter it’s not so obvious. So how do perennial plants like trees and grapevines respond to winter weather?
Grapevines, like all woody plants, take cues from the environment. During the long days of summer, the vines are growing and making grapes. They could not go dormant during that period if they had to. But as the days grow shorter toward the end of summer, the vines are able to detect that the change of seasons is coming and respond by storing starch reserves in their roots and trunks. They detect a change in the ratio of red light to far – red light that occurs as the days grow shorter. The green shoots that grew all summer begin to turn brown and woody so they can over - winter and carry next year’s crop. As the shoots turn brown or “lignify” they become tolerant of cold temperatures and can survive a frost. As the crop ripens the plant becomes more and more prepared for the cold winter months ahead. Finally, the leaves fall and the vine becomes dormant.
So what happens if there is warm weather during the winter? As it turns out, the vines do not achieve their maximum level of hardiness until there has been sub-freezing temperatures for several days. The vines become more tolerant of deep cold as they head into the coldest part of winter. During this time the vines are in what is called “enforced dormancy”. During this period they cannot begin to grow, no matter what the weather does. If you took a cutting of an over wintering cane into your house and put it in water it would not grow. This protects the plants from responding to warm temperatures and starting to grow in the middle of winter. As winter continues however, the vines are able to measure the passing of time so they “know” when to begin growing. The actual mechanism is not fully understood but the plants need a certain amount of time at temperatures between freezing and 40⁰ F to complete what is called their “chilling” requirement. This mechanism gives the plants a way to measure time during winter and allows them to begin coming out of dormancy once the chilling requirement is met.
The period when enforced dormancy ends is called “eco-dormancy” because now the vines depend on cool temperatures to keep them dormant. Once the temperatures warm the vines begin to grow again.
Understanding that plants have a way to measure time while dormant is fascinating and it helps us understand when plants might become vulnerable to environmental damage like winter injury or frost injury in spring.
Let’s look at our current weather for an example. The weather turned cold in December and stayed cold for several weeks. When the temperature stays below the freezing point the plant gets no chilling time. Now, in January, we are having a thaw and the temperatures are forecast to be above freezing for a week or more. During this time the vines are fulfilling their chilling requirements and are moving closer to being able to begin their climb out of deep dormancy toward bud burst in spring. What we don’t want right now is too much of this mild weather. If that were to happen the vines might begin to come out of deep dormancy before the coldest part of winter has passed which might lead to winter injury. Additionally, the more chilling the vines get now the sooner they will be likely to come out of dormancy. This sets the stage for early growth and then frost damage in spring. That’s what happened in 2012 when we had 10 days of 80⁰ weather in March. All of the fruit trees started to grow and bloomed. Then there were a series of frosts in April that killed the blossoms and there was virtually no tree fruit in Michigan that year.
So even in the middle of winter, the woody plants are alive and sensing the environment around them. They are measuring the passing of time and getting ready to start growing in spring so they can make another crop and complete another growth cycle. It is truly an amazing process and we have the privilege to watch it happen – if we just take the time to slow down and look.
17 January 2017
Welcome to White Pine Winery!
White Pine Winery showcases Southwest Michigan’s finest wines and warm hospitality in our lakeshore destination in the charming town of St. Joseph. We produce a range of delicious red and white wines and specialize in aromatic whites like Riesling and Pinot Gris and fruit driven reds like Syrah and Merlot. These varieties grow particularly well here given the lake effect which brings warm days and cool evenings to the vines during the important spring and fall growing seasons. Owner and winemaker, Dr. David Miller, is a noted winemaker and viticulturist with over 30 years of experience. Named after our state tree, White Pine characterizes Michigan’s natural beauty. We invite you to visit our tasting room at 317 State Street.
Winter is the slow season in wine country but that doesn't mean there is nothing to do. Michigan is a winter wonderland with snow, ice, frost and amazing sunsets over the Big Lake that seem to last forever. And, you can catch sunset before dinner time! The tasting room is less crowded so you can have time to savor wines and talk about them with our staff or, visit on Thursday's when Dr. Dave, our winemaker, works. He can share with you some of the nuance of producing fine wines and talk about the new wines he made last fall. There are some great wines in the tanks that will be available this spring and summer. Stay tuned for special tastings!
Wine Tasting at White Pine Winery:
Wine tasting is $6 to taste 6 wines. There is no charge for the tasting with the purchase of 4 or more bottles of wine. Groups of 7 or more should call ahead to reserve a time for tasting.
Spring hours (March through May): Sunday through Thursday: noon to 5pm; Friday noon to 6pm; Saturday noon to 5pm. Closed Easter Sunday
Summer Hours (Memorial Day through Labor Day): Monday - Thursday 11am - 6pm; Friday and Saturday: 11am to 7pm; Sunday noon to 5pm.
Fall Hours (September and October): Sunday through Thursday: noon to 5pm; Friday noon to 6pm; Saturday 11am to 6pm. Closed Thanksgiving Day
Holiday Hours (November and December): Sunday through Thursday: noon to 5pm; Friday noon to 6pm; Saturday noon to 5pm. Closed Christmas Day and New Years Day.
Winter Hours (January and February): Thursday: noon to 5pm; Friday noon to 6pm; Saturday and Sunday noon to 5pm. Closed Monday, Tuesday and Wednesday.
From the time we prune the vines in March until the last fermenters are racked, the vineyard and winery are busy…. Very busy places. The vines require regular attention during summer as do the new must and wine following harvest. But winter is a time to slow down and recharge. It is a time of rest for all – the vines, the wines and the people involved. During this time in the wine cellar, it may not look like much is happening but it is really a magical time.
The wines cold stabilize with the drop in temperature. This simply means they won’t develop a tartrate sediment in the bottle when you chill them in your fridge but there is also a drop in acidity which softens the wine and takes off some of the sharp acidity of the new wine. Carbon dioxide from the fermentation comes out of solution during storage which further softens the new wine. The wines also clear as particulate matter slowly drops out of the wines during the months of rest. Other things are happening in the wine now that can’t be seen but can be tasted and felt on the palate. There is a chemical change in the wine as new flavors develop from the interaction of various wine components and the alcohol that developed during fermentation. The changes produce aromas and flavors that begin to make the wine more complex and interesting. In red wines there is a change in the pigments and tannins (compounds that contribute to astringency on the palate) that softens the wines and enhances the color. Wines aging in barrels extract flavor from the wood that also interacts chemically with flavors, aromas and pigments in the wines, further contributing to the complexity in aroma and on the palate.
As we taste the wines from tanks and barrels we can begin to gain a better understanding of what is to come and what the wine might be like when it “grows up”. It’s an exciting time because some of the wines are really good! There is not much to be done by the winemaker at this point, just make sure tanks and barrels are topped and that there is no activity by unwanted spoilage bacteria or oxidation due to headspace in a tank. If we did a good job in the vineyard, had a bit of luck with weather during the fall, and paid attention to winemaking fundamentals, then we know the wines will be special when they are bottled and will only improve over the next couple of years or more, depending on the wine. It really does seem magical to observe the changes occurring to the tasted and feel of the wine.
Then there is the natural beauty of our winter wonderland! Come see for yourself. We'll have some wine to share.