#6: The Sex Life of Grapes. (PG-13)! Journey to Harvest…and Beyond!

Grapes Have a Sex Life????

Yep!  Amazing as it may seem (and one way or another), all plants and animals, in order to reproduce, have a sex life.  And not only do our wine grapes have a sex life, they are truly hermaphrodites!  Before you burn this seemingly R-Rated column, a hermaphrodite, in the world of botany, is simply a plant that possesses both male and female reproductive organs and doesn’t need another plant to reproduce.  Magically, that is the way almost all grapevines self-pollinate and self-reproduce!

 In The Plant World, Is It Better To Be a Hermaphrodite?

It surely is!  The survival of any plant species depends on its ability to easily reproduce.  If a plant only requires itself to reproduce, the chances of successfully creating and duplicating the next generation are greatly increased.  The fruit that is created each and every year tends to be less erratic.  And the wine made from that fruit tends to be consistently “better”.  What a huge advantage it is if the plant is not dependent on insects or birds to carry pollen from one plant to another.  Our wine grapevines have evolved so much that, in botany, a plant that has both reproductive parts is called a “perfect” plant, and it produces “perfect flowers”.  (Further argument that while wine grapevines are “perfect”, we humans are “imperfect”) 

 Don’t Grapevines Need Honeybees to Pollinate?

Nope.  Our present-day, European-originating wine grape varieties (Vitus Vinifera) are plants that have evolved over the Millennia so that both genders are contained within each grapevine.  Thus, they are “perfect”.  All those grapevines that produce the wines we are familiar with (Syrah to Semillon, Pinot Noir to Pinot Gris, Cabernet Sauvignon to Chardonnay) do not need another grapevine to complete pollination and reproduce. Each of those hermaphrodite grapevines produces its own “perfect flowers” that have both male and female reproductive organs.  (Isn’t that just “perfect”?) 

 What About Those Honeybee Boxes Around the Vineyards?

Many grape farmers (particularly bio-dynamic farmers) do have honeybee boxes near and around their vineyards, but that isn’t for grapevine pollination.  The bees (and birds) are responsible for taking pollen from one “imperfect” plant to another for cross-pollination.  Why do that?  Because those other plants around the vineyards, from cover crops to rose bushes at the ends of vineyard rows, attract  beneficial insects to combat other insects that may endanger the grape crop.  Those “imperfect” plants need honeybees for their successful pollination.

 How Do Grapevines Self-Pollinate?

After the leaves fall off in the Winter and the vines go dormant, we severely prune back our grapevines, leaving only the essential numbers of buds. In the ensuing Winter months, the grapevine rests to store its energy, patiently awaiting Spring when the temperatures will rise and those buds begin to think about producing offspring.  Finally, the warmth of the Spring growing season will cause those tender young buds to swell up and green tissue begins to emerge and begin the reproductive cycle.  In grape growing, we call that moment “bud break” or “bud burst”.

After a month or so of growth (seemingly overnight), each of those buds will magically produce small, tight bunches of tiny flowers, and every single one of those flowers has the potential to produce one grape berry.  This is where the alchemy of self-pollination begins!  Each and every tiny, newly-formed “perfect” flower in those mini-clusters has a female reproductive organ (ovary and pistil) along with the male portion (stamen) and on each stamen is an upright portion (anthers) that contains the pollen needed for fertilization.  Self-pollination is a complex process but, in a perfect world, each of those “perfect” flowers will successfully pollinate and develop into a grape and those single grapes together become a grape cluster.   

What Could Possibly Go Wrong?

Lots of things.  Anything that disrupts individual grapes from developing in a cluster of grapes is called “shatter”… a mixture of mature and never-to-develop grapes. (Farmers also refer to that phenomenon as “Hens and Chicks”.)  At the end of that pollination process when the pollinated small flowers grow in size and turn to berries, the farmer can tell how successful the process has been.  No matter how much or little shatter there has been, the farmer now has a pretty good idea of what the crop load will eventually be.  The word for that moment is “set”.  (This is the time of year when our grape farmers will greet one another at the market or the post office with “How’s your set this year?”)

What Causes “Shatter”?

Almost always, Mother Nature is the culprit.  During that crucial time of self-pollination, anything that might disrupt pollen from reaching the female portions of the flower will cause shatter.  There could be rain or even heavy morning mist, there could be too much wind, too much heat, not enough heat, an untimely frost, a nutrient imbalance, or even a mis-timed sulfur spray.  Yep, lots of things could go wrong.  

Does Self-Pollination Ever Work Perfectly?

It sure does!  Mother Nature may be very fickle, but sometimes she does choose to cooperate!  It is never an absolutely 100% set, but much of the time we get pretty lucky!

As one grapevine said to the other: “Oooooo! Isn’t it good to be “perfect”?