There’s a common adage that floats around when people discuss viticulture that the vines must be stressed during the season to produce wonderful grapes for the harvest. Those of us that know little about horticulture, take a sip of wine so we don’t have to talk, nod politely and associate this with the romanticism or mysticism surrounding wine. I’ve come to discover that most of the people who state this adage emphatically, have no idea what they are actually talking about. When you press these people for more on the topic, they mumble things about poor soil quality, restricting water and maybe add the word terroir randomly before quickly changing the subject (worked for me!). To relieve the suspense up front, it isn’t that this old saying is wrong, it is very right. But I try not to go around saying things when I don’t know what they mean.
While the title of this post may seem a bit cheeky, I promise I’m not misleading you (too much anyway). Without further delay to your knowledge gratification, let’s get down to the dirty business of stressing the vines. I’ll try not to let too much hot vine on vine action get in the way of what I’m trying to say.
Plants generally reproduce in two ways: one is called vegetative reproduction which can be thought of as plant growth or self-replication and the other is good ol’ sexual reproduction. Concerning our beloved grape vines, vegetative reproduction is when the vine puts the energy it is generating into growing the vine and its roots. Sexual reproduction is where the vine puts the energy into making seeds so it can further its genetic line elsewhere. Jamie Goode puts is wonderfully in his Science of Wine book:
Generally (and simplistically) speaking, if conditions are good and a plant is doing well, then, if it can, it opts for vegetative reproduction or just grows larger – after all, there’s clearly a good match between the plant genes and the environment and it wants to keep things that way. On the other hand, if conditions are bad, plants will more often choose to reproduce sexually (the “I’m outta here” option), which requires fruit production.
Let’s talk about the Birds and the Bees, shall we? A vine may reach a certain point in its life where it gets that “funny feeling”. Of course, in this instance, the feeling is the realization that the vine’s current home, terroir if you will, just isn’t working out and it needs to sow its seeds elsewhere (literally speaking) to continue the genetic line. Through the course of evolution, the vine has developed symbiotic relationships with certain insects (i.e. bees) as well as animals (mostly birds). Never one to go it alone (seriously, they’re so dependent), when the vine decides it needs to reproduce, it grows flowers which signal the bees to do their thing on itself or with other vines. Come to think of it though, domestic vines are mostly hermaphrodites so I guess there is really just a lot of “self-pollination” going on.
After the bees do their part and the grapes start to grow, the vine cues the birds. [Birds enter, stage right and all aflutter] The “cue” in this case is when the grapes turn from small and hard grapes, to fat and juicy ones. In the viticulture world, they call this point veraison. Now, grape growers wait a bit after this to pick the grapes because they develop a little more after this point, but this is the dinner bell for the birds to swoop down and eat the calorie-filled tasty treats while swallowing the seeds whole. As one would assume, birds and farmers generally do not get a long very well. I don’t need to describe the seed extraction process from the bird in detail, but the hope is that the bird does that elsewhere and in a lovely new home for a future vine.
Which brings us back to stressing the vines. For the best possible grapes, we need a good strong vine that puts a lot of energy into producing fruit. If everything is dandy in the vine’s world, it won’t feel the need to spread its seeds which means little or no fruit. On the other hand, if things are absolutely horrible, the vine won’t spend anytime doing personal development, it will just be in eject mode which means a weak vine. Therefore, you have to give your vine everything it wants (adequate amounts of water and sunlight and maybe some supplemental minerals) to get it nice and strong and then “stress” it or deny it some of its needs just enough to get it to feel the need to produce fruit.
How you do that is both an art and a science, depends a lot on the terroir (geography, climate, weather, etc.) and what grapes you are growing. Because the weather changes every year, there is a level of unpredictability in what the vine will need each year to get to that balance of ideal vine and fruit growth. A great season weather-wise will do most of the work, but this doesn’t always happen. This is why there is much ado about vintages, but that is a subject for another post.
OK, so this post really should have been titled: “Stressing the Vines” Is All About Sex(ual Reproduction)! But hopefully I threw in enough hot vine on vine action to keep you satisfied. Whatever you do with this information, please, please, pleeeeaaase do not tell those vines that we are stealing their children and using them to make a heady beverage. Let them think their seeds are settling in greener pastures and leading a better life than they ever could have had. Perhaps, it is best to keep them in the dark about this one. For our sake’s anyway. They may end up coming after ours.