April Showers Bring May Flowers...

…and what do May Flowers bring??

Up until a few weeks ago, I would have gleefully shouted PILGRIMS!! along with the large majority of elementary school-aged children plaguing their parents with this old-but-new-to-them riddle. What can I say? I enjoy a good (read: horrifically bad) pun as much as the next person.

But this year I have a new answer. May flowers bring…GRAPES!!

So much more exciting (and colorful…) than Pilgrims.

The other day I was sitting in the office, bemoaning the capricious weather that we’ve been having since, oh mid-February and wondering aloud when it would ever be spring. Then Griff said something interesting: Well, we certainly don’t want it to warm up too soon or too quickly.

Ohhhhhh riiight. The vines. Late frost. I tried to look knowledgeable, but my ignorance must have shone brightly because Griff took pity on me and tried to explain budbreak and the growth cycle of the vines and…well, I got lost pretty quickly.  

So, I decided to do a little research and figure out exactly where we are in the growth cycle (currently, somewhere between weeping and budbreak, which will happen to most of our grape varieties around mid-April).

Weeping, as Griff so eloquently explained to me, is the period of the vine’s yearly cycle in which the sap begins to warm and seep slowly through the vine, bringing it back to life. When the sap reaches the previously dormant buds, we have budbreak.

Shoots develop from these buds, and “even when the shoot is only a few inches long, developing flower clusters can be seen opposite the young leaves” (Hellman 15). “As the shoot grows, considerable development takes place….Of greatest interest is the [flower cluster initiation], since [the flower clusters] represent the fruiting potential of the vine for the following season” (Hellman 15). The flower cluster primordia will develop either into flower clusters (which will eventually bear fruit) or tendrils, “depending on environmental and growing conditions experienced by the specific bud and the shoot in general” (Hellman 15).

After the flower clusters are successfully pollinated, the berries begin to grow. “Flowers with unfertilized ovules soon shrivel and die, while those remaining begin growth into berries” (Hellman 16). This sounds a little dramatic, so it’s important to note that “commonly, only 20-30% of flowers on a cluster develop into mature berries. [Fortunately,] this is adequate to produce a full cluster of fruit” (Hellman 17).

There are three stages of berry growth: “rapid initial growth,” a “middle stage called the lag phase,” and another period of rapid growth” (Hellman 17). This last stage is called veraison, from the French for ripening, and “is discernable by the start of color development and softening of the berry” (Hellman 17).

In his report for Oregon Viticulture Hellman points out that “berries are considered to be fully ripe when they achieve the desired degree of development for their intended purpose” (Hellman 17). In my unschooled effort to determine when grapes are ready for harvest, I didn't find this vague generalization/statement of the obvious terribly helpful. But Hellerman does go on to later explain that the “ripeness factors typically considered when scheduling harvest are the sugar content, acid content, pH, color and flavor” (Hellman 17). A little clearer, but still dependent on some knowledge of how sweet or acidic or deeply colored the grape should be. Basically, the moral of this paragraph is: pick them when they taste right for making wine…if you’re not sure what that taste is (and I’m certainly not) experiment and/or ask an experienced vintner for his or her opinion.

Following the harvest, the vines go dormant for the winter months, a process in which they acclimate themselves to the cold and develop cold hardiness, then deacclimate in the spring, beginning the cycle over again.

For pictures of the various stages of growth, visit: http://www.grapes.msu.edu/pdf/Growthstages.pdf

Bibliography

http://aggie-horticulture.tamu.edu/faculty/hellman_structure.pdf