Fall colors: Grapes turn red, yellow

Late summer brings veraison to Colorado’s vineyards.

This is the time when grapes change from green to red or yellow and develop their characteristic mature colors.

It’s also the time when a grapevine changes its focus, if you will, going from producing the heavy mass of leaf canopy and root system and devoting the summer’s worth of stored energy into producing ripe fruit.

Whether it’s the golden-green of Chardonnay, the dark blueberry hues of the thin-skinned merlot or the almost-black thick skins of syrah, the changing berries are a key sign to grape growers of how well their efforts are paying off.

If you’ve ever wandered a vineyard in late August or early September, you would have noticed veraison isn’t consistent and doesn’t occur simultaneously in the same row or even on the same vine.

You might find grapes at 50 percent veraison at one end of the row, and halfway down the row the grapes might be 100 percent veraison.

Or opposites sides of the same vine, depending on their shading from the sunlight and heat, might be drastically different.

Winemakers always look for consistency, and if there are some bunches too lagging in development, the less-developed bunches might be dropped (also called green-cropping) since they probably won’t ripen in time for harvest.

They might turn color in time for harvest, but they still will be far behind in ripeness and those under-ripe grapes can affect the taste of the finished wine.

Red grapes that aren’t fully ripe have low sugar levels, lack flavor and color and are high in acid.

They give wine a tart, herbaceous flavor, often described as green bean or bell pepper, although some winemakers prefer a little “green” taste in their wines.

Less-than-ripe grapes also don’t have the color, which comes from the skins.

There always are exceptions, of course. pinot noir can be fully ripe and still the wine might be light red, barely opaque and yet quite delicious.

Dropping the unripe bunches also forces the vines to send more energy into the remaining clusters.

Which is why, if you walk a vineyard this week, you’ll see more bunches than you might see in a month or so.

If you cut back by a third, the vines send that much more resources into the remaining grapes and, theoretically, this should produce more intense flavors.

As the grapes continue to ripen from beginning of veraison to harvest, the berries increase in volume, weight and sugar content, which commonly is measured in brix.

Veraison isn’t a sign that harvest is pending, although it does offer some hints to grape growers how long they have until harvest.

While one rule says it’s 45 days from veraison to harvest, there’s really no way to tell because so much depends on Mother Nature.

Veraison also marks the end of the vine’s growing season. Instead of putting its energy into new growth, the vine expends its resources on producing ripe fruit.

It used to be the seed getting all the vine’s attention, but now the entire berry starts to ripen.

Winemakers follow the process by measuring grape sugars, development of the grape skins and, perhaps the most traditional method of all, biting into a seed to determine its ripeness.

A still-green seed is full of bitter tannins while ripe seed is brown, with softer tannins and almost a nut-like taste.

But it’s not sweet. A wine’s tannins, those mouth-puckering factors that add to a red wine’s longevity, come from the skins, stems and seeds, so chewing a grape seed can be a startling experience.

Another product of veraison is the arrival of aerial predators.

Grapes originally depended on the digestive systems of birds and animals to spread their seeds, and the darkening grapes are a siren call to the flocks of robins, starling and blackbirds you’ll see wheeling around the valley in late summer.

One winemaker said he’s lost nearly an entire vineyard to a flock of blackbirds, whose appetites belie their tiny size.

That’s why you see the miles of bird-proof netting covering the vines, saving the ripe fruit for the human pickers.

Initially, the netting simply was draped over the vines but it didn’t take long for some birds to figure out how to fly under the netting and up into the vines, where they could eat undisturbed.

Now, either the netting reaches the ground or is tied under the vines, another step in the winemaker’s battle against Mother Nature.

Ironically, the word “merlot” is thought to have come from the Old French word for young blackbird.

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