Cover your assets - “weeds” in the vineyard

Like our own desks and houses, every vigneron has a certain look about his or her vineyards. And just like desks and houses, some are neat as a pin, others look like someone set off a mess bomb in their midst, while others still are somewhere in between. So the obvious question here is “why”? Are some growers anally retentive while others are just slovenly housekeepers? In some cases, the correct answer is an unequivocal “yes”, and it’s just as simple as that, but in MOST cases, the decision to allow a vineyard to go “wild” is a conscious one.

The technical term for this phenomenon is “cover cropping”. Cover crops are best defined as non-vine plant species that are allowed to grow, or are actually consciously planted, and to some degree, cultivated within a vineyard as aids to improving vineyard health and/or fruit quality improvement.

Cover crops can take many forms. In quite a few instances, cover crops encompass nothing more or less than “weeds” that grow where they will, and that are simply not “weeded out”. Stuff grows will-nilly, and god bless it - in non-cultivated areas around vineyard sites, in the spaces between the vine rows, and even directly under the vines themselves. The other sort of cover cropping comprises specifically selected plant species that are consciuosly planted in certain areas in the vineyard, but often in “off” times that do not interfere with pruning, harvest, etc. There are also “canaries in coal mines” plants that can serve as warnings for pending difficulties for the vines themselves. For example, roses are often planted in more humid vineyards or alongside vine varieties that are particularly susceptible to maladies brought on by excessive humidity because roses will succumb more quickly to the advances of a disease like downy mildew than the vine will, thereby allowing the grower to take preventive rather than curative action.

So back to the original question of “why”? All cover crops accomplish certain things no matter what the species, and where they are found:

- SOIL STABILITY - Depending on soil type, and even more importantly on rain patterns and vineyard steepness, soil erosion can be a major problem on certain sites. A cover crop’s root system provides a structure to which soils can cling, thereby reducing simple erosion difficulties.

- INCREASE IN ORGANIC MATTER - Weeds, crops, etc. attract insects, worms, etc. These organisms do their respective “jobs”, and leave their waste, and eventually, their remains, as well as these organisms’ predators who in turn leave their “leavings”, attract their predators, and so on, and so on, and so on, and this is not to mention the dead matter that emanates directly from the cover crops themselves in the forms of pollens, dead foliage, etc. …those growers that espouse organic and Biodynamic viticulture argue that these sorts of “living” vineyards produce more complete and expressive wines than sites that have been “pesticided” to within an inch of their lives.

- WATER RETENTION - In exceedingly dry growing regions, every drop of water is precious, and “bald” vineyards have much greater difficulties in holding this precious commodity. Cover crops in many cases can relieve the grower from the expensive and time consuming process of irrigation, and in some cases, cover crops can be the very reason why the vineyard exists at all for regions that do not allow irrigation in any shape or form.

- WATER STRESS - With lots of other plants in a vineyard, each of which drinks a bit of water each day, a certain amount of water deprivation to the vines can occur. Clearly in EXTREMELY arid conditions, crop covering must be carefully studied and judiciously employed, but water-stressing vines can effect two important vine behaviors. First, water-stressing vines causes an earlier onset of ripening which under certain conditions can be a benefit to the grower. Second, depriving vines of water “stresses” them, causing them to push their roots deeper into the earth to look for water, which also means further into the poorer, more inorganic matter-rich soils that are said to be a huge part of what constitutes “terroir”.

- NITROGEN ENRICHMENT - Certain specifically cultivated cover crop species like particular species of winter legumes, though they can reduce soil nitrogen in the spring, when they are ploughed under in the late fall, can RETURN large quantities of nitrogen to the soil at a time when the soil wants to give it up.

But as has been alluded to above, there can be some downsides to crop covering, or least potentially so. Using cover crops to regulate water obviously requires that one also tends these plants to meet one’s growing needs. For example, if one is growing cover crops to RETAIN water in a vineyard, one has to be sure that the crop chosen is not a particularly “thirsty” species, and if one is simply allowing for spontaneous weed growth, that these weeds do not overgrow and begin to rob precious water from the vines. Further, heavy cover cropping can increase the chance for frost damage in the cooler months because heavy cover cropping helps to retail the coldest air that settles on the ground in a vineyard. Even too much or the wrong cultivated cover crop can deprive a nitrogen-challenged plot just when the vines need it the most which can lead to stuck fermentations (the unwanted slowing down or even cessation of the fermention process) after crush.

There are indeed quite a few growers that overtly DISCOURAGE the growth of anything but vines in their vineyards, but the current of opinions now seem to be flowing in the direction of more rather than fewer cover crops, but with the job of viticulture already rated at the “brutally difficult” level, for some the added work of tending weeds or lupin beans is simply unconscionable, perhaps both physically as well as financially. But those who embrace cover cropping argue that those who don’t may be stealing from Peter to pay Paul, and therefore costing themselves time and money in the long run.

The cover crop controversy will surely continue, and most candidly, there are vineyards for which this is decidly NOT a good idea, but with the advance of knowledge about biodiversity on every level, and the free and unseen benefits of promoting it, it seems that the employment of the technique will continue to proliferate.

TOM CIOCCO