Rain, at least at this time of year, is a four-letter word for winemakers. Once harvest begins, they don't even like to look up. (They can be superstitious that way.) Bad things sometimes happen to good grapes, and while there's no reason for consumers to have sleepless nights over thunderstorms and heat waves, the occasionally nasty whims of Mother Nature can certainly affect how a wine tastes.
What follows is a consumer-friendly guide to the pitfalls and heartaches that sometimes come with harvest, and what they all mean to wine drinkers.
Temperature has everything to do with how grapes mature, and therefore how a wine tastes. It's all about ripeness.
Think of it this way. Burgundy is cooler than California, and that's one reason that Chardonnays from both regions taste different, with white Burgundies generally showing more tart apple and citrus flavors, and less of the ripe tropical fruit typical of California wines.
Even warm climates can have unusually cool growing seasons, but whatever the climate, if it's too cold for too long, grapes suffer. The same is true of strawberries: If they're not ripe, they taste overly tart and have less flavor, but as strawberries ripen and their flavors mature, they taste sweet, juicy and rich.
Acidity is key. As grapes ripen, they lose acidity, and the juice from the grapes goes from tart to sweet. Of course, wines needs acid to make them taste vibrant, but if temperatures are too cool for too long, the grapes won't fully ripen, and the resulting wines will taste aggressively tart or even sour.
Unripe grapes also produce wines with undesirable "green" qualities. Cabernet Sauvignon might smell like bell peppers or Sauvignon Blanc might taste like asparagus.
Sure, it takes heat to ripen grapes, but sometimes it gets too hot for grapes to handle. If the growing season is extremely warm, all sorts of problems can occur. The grapes can dry out and become overripe. Instead of a Zinfandel smelling like fresh raspberry or cherry, it may have a not-so-lovely raisin bouquet.
Since fermentation involves the conversion of sugar to alcohol, grapes that are overly ripe and high in sugar become wines that have an alcoholic burn and often taste unbalanced and one-dimensionally sweet.
If there's one thing that winemakers hate at harvest, it's a cloudy sky for days on end. Overcast and soggy weather isn't the automatic disaster it used to be, thanks to technology and lessons learned from a few "harvests from hell," but it still makes for long days and sleepless nights in wine country.
Too much rain in the spring can be a problem as well. A hard rain while the vines are flowering will knock the blooms off the plant and reduce the size of the crop. And damp conditions during the growing season may lead to mildew and other diseases. (See below for more.)
A wet growing season or harvest can affect the taste of a wine in subtle and not-so-subtle ways. Overcast skies mean a lack of sunlight, which causes grapes to struggle to ripen. Also, grapes actually bloat (and sometimes burst) with water during rainy weather, and without an additional dose of sun and heat, the resulting wines might taste thin and diluted.
Too much of a good thing
Even a perfect growing season has its pitfalls, such as overproduction. If the weather is favorable and the crop gets too big, the quality of the wine may suffer. Winemakers are convinced, for a number of reasons, that a vineyard growing 3 tons of grapes to the acre produces more flavorful and complex wines than a vineyard that grows 6 tons an acre. So when a crop is too large, growers may trim off extra grape bunches, doing what's called a "green harvest," before the grapes ripen -- as many have done in California this year.
And the rest ...
Frost is a concern in many regions, particularly if it hits when the vines are budding with new young shoots or later on when the vines are flowering. Frost damage won't affect the taste of a wine, but it may cut the size of the crop and translate into fewer wines on the shelf for consumers. Growers often go to great lengths to protect the vines from frost damage. Sometimes growers light smudge pots in hopes of blanketing the field with protective smoke and turn on giant fans in the field to keep the frost from settling on the vines. Ironically, if the field is irrigated, one of the best ways to protect a vineyard is to coat it with water, insulating it from damage.
Flooding typically occurs in the winter, when vines are dormant, so they suffer little or no damage. But, as happened this summer, floods occasionally strike in Europe during the growing season, swamping cities and fields. Austria's wine regions are still drying out and trying to assess the damage. Floods during the growing season leave waterlogged grapes that can burst and spread mildew and other diseases, potentially ruining a crop.
Hail devastated many vineyards in Northern Italy earlier this month, particularly in Valpolicella, Soave and Bardolino. At its worst, hail shreds the leaf canopy (if the leaf loss is severe, the vines can no longer grow properly) and batters and breaks the grapes, damaging and reducing the size of the crop. Hail storms are often localized, wreaking havoc in one vineyard, while leaving neighboring sites untouched.
Pests and such
We aren't the only ones with a taste for grapes. Any number of bugs, creatures, fungi and bacteria like to nosh on vines and grapes, and some of those spread or cause diseases that are deadly to the plants. Consumers will feel the effects more in their pocketbooks than on their palates, as growers spend millions a year keeping vineyards healthy.
Mildew, rot and other fungi are easily dealt with by growers, except under extremely wet weather conditions, with the help of fungicide and severe thinning of diseased fruit. Still, consumers may come across the occasional wine that has off-flavors and moldy aromas. But rot isn't always a bad thing, particularly if it's Botrytis cinerea, the so-called noble rot, which help make Château d'Yquem and other famous dessert wines possible. It attacks grapes under certain climatic conditions and causes them to shrivel, deeply concentrating the flavors, sugar and acid.
Anyone who tends a garden knows that birds can be a headache -- they've been known to pick a vineyard clean. If you tour a wine region, you'll occasionally see vineyards covered in netting to keep the birds off, and if you've ever noticed the metallic streamers glimmering in the vineyard like Christmas tree icicles, those are thought to ward of birds as well. Deer -- and even the occasional bear and wild boar on the West Coast -- enjoy a meal of grapes now and then too.
While consumers haven't noticed a difference in the bottle -- except perhaps for a higher price tag -- two little bugs have continued to panic the wine industry, particularly in California over the past few decades.
Phylloxera is a tiny aphid that feeds on the roots of a vine and kills it over the course of several years. In the 1990s in California, thousands of acres of vineyards -- once thought immune to the pest -- had to be replanted with resistant rootstock at a staggering cost. For now, phylloxera seems in check.
The glassy-winged sharpshooter is getting most of the attention in California these days. The insect spreads Pierce's disease, which kills a vine in five years or less and can't be cured. So far, only vineyards in Southern California have been widely infected, but glassy-winged sharpshooters are occasionally spotted in Sonoma, Santa Cruz and other Northern California regions. Prior to the arrival of the glassy-winged sharpshooter, California had already faced sporadic outbreaks of Pierce's disease spread by the less-vigorous blue-green sharpshooter, which breeds around rivers and streams.