Pruning


In the immortal words of Jim Morrison, This is the End (of the Glog).  It has been a fun, educational tool for me to communicate with growers and I hope that you found it useful.  This is the last entry, but it will remain up for reading — at least for awhile.  I will start a new blog sometime after I start at Mississippi State University and it will be on http://www.eviticulture.org.  Some other capstone items I wish to say:

1. Please continue to support OSU’s viticulture and enology efforts.  Just because I am leaving does not mean the program just goes away.  And if you would like to see my position refilled (that is not guaranteed!), I suggest developing a strategic plan to make this happen.  Contact the appropriate people (department heads, deans, provost, president, legislators, anyone with influence — and money), find a way to provide some funding to support research and extension efforts and do it on an annual basis, and come up with a plan of attack that may include having discussing with folks in the pecan industry.  It is unlikely that the position will be refilled solely as a grape position, but as a joint position with pecans is possible.  A plan of action may look like this: rally support for filling the position within the industry by drafting a position paper on why it needs to be filled as soon as possible, develop a plan for funding assistance to do the work you need done through research and extension, develop strong relationships with the OSU horticulture dept head and OSU division of agriculture dean.  If they don’t know you exist, then they won’t care.  How many times since 2005 (when I started) has anyone in the industry interacted with the dean?  I don’t know the answer to that, but if it is 0 or a very few times then that does not bode well.  A plan of action must include items like “why the position is important to the industry”, “what does the industry bring to the table in order for the university to invest in the position”, “how is the industry growing and what are future projections such that a continuing presence is needed?”.  Think about resources that might be available for an extension specialist to use (in-kind services, etc.).  In essence Why does the grape and wine industry of Oklahoma need this position to be filled and what is the Oklahoma grape and wine industry prepared to do about it?

2. Contribute your voice to an industry organization and keep abreast of what is happening in the industry now.

3. Don’t forget to read my last issue of Le Vigneron (to be published sometime early October).  It will include some photos of our vineyard, data and interpretation of the Perkins vineyard since 2002, and some other goodies.  At this point I don’t know if it will be the last one or not, but it will be a “blow-out” issue.  If you are not on the mailing list you can always find it online here (www.grapes.okstate.edu).

4. Growers and wineries need to stick together and display a unified front to legislators.  Find a way past the differences and work together.  To be honest, other states have really gotten their acts together and formed cohesive state organizations that get a lot done.  It might be a good idea to talk with leaders from other states that are on a similar scale to Oklahoma  (like Kansas, Minnesota, Iowa, Nebraska, etc. to find out what they are doing that is successful).

5. Be leery, but not dismissive, of vinifera grapes.  Well, maybe dismissive in many parts of northern Oklahoma.  Vinifera grapes can grow in Oklahoma, but we are concerned not only with growth.  We are also concerned with productivity, survival, disease resistance, and fruit quality.  Through my six years here I have come to these conclusions: Vinifera grapes are high-risk and should not be a first choice north of I-40.  South of I-40 on excellent sites they can be considered but not all varieties work.  Always use a rootstock, preferably a low vigor rootstock like 101-14.  Economics must be a prominent thought in variety choice.  What price per ton can be obtained?  How much does it cost to maintain per acre per year?

6. Open your mind to hybrid grapes.  There are many good varieties out there.  The only way to learn about them is to taste the wine and view the vine growth.  There are opportunities to do this within Oklahoma as well as in surrounding states.

7. If you have not done so already, please complete this survey:

https://okstatecasnr.qualtrics.com/SE/?SID=SV_agjMhFmvr6f4TMo

8. Attend conferences such as ASEV, Unified Symposium, Midwest Grape and Wine Conference, etc.  The national perspective you get from these types of venues are invaluable.

9. Stay positive.  Oklahoma is a difficult place to grow grapes, but it can be done (with proper variety selection, site selection, management, and education).  Setbacks will happen, but Oklahoma has a terroir different from anywhere else, so it is exciting to be able to taste that through the grapes.  Taste Native Oklahoma is something to strive for.  Will it be possible to have an industry built entirely on Oklahoma grapes?  I don’t know, but at this point it is unlikely and impossible.  However, with a positive attitude anything is possible.

10. Not sure what else to say, but I wanted to have 10 items here.  So, as Bill S. Preston, Esq. once said, “Be excellent to each other.”

Yes, the end is coming soon for this blog.  When is the last day?  I’m not entirely sure, but probably somewhere around September 22.  The reason?  Well, for one thing I am leaving on the 23rd to give a talk at a conference in Hawaii.  Secondly, if you have not heard by now, I am leaving OSU on October 14.  I have been offered, and accepted, another position similar to this one at Mississippi State University.  I start there on November 1.  I will still be in the grape world — I will continue to be the Project Leader of eViticulture.org and I will start a new blog that can be read from that website.  It will no longer be Oklahoma specific, but I will touch on grape growing in the Deep South as well as other broader topics of interest.  There are many loose ends concerning how things will continue here at OSU, but meetings will be held to discuss those things and we hope to have a plan in place before my departure.  I have really enjoyed doing this blog and I hope you will continue to follow me when I move over to my new blog.

My colleague at Penn State University, Mark Chien, sends out an email newsletter that contains all kinds of great info throughout the season.  Although focused on Pennsylvania and the mid-Atlantic region, there is application of many of his writings to the rest of the country.  In his latest issue he reviewed a new book by John Gladstones called “Wine, Terroir, and Climate Change”.  I have not read this book yet, but Mark gives a good review of some of the key components.  Gladstones wrote a previous volume entitled “Viticulture and Environment” — a classic in the field.

To get to flavor and pigment development, Mark summarized this from Gladstones latest book:

“Flavor and pigment development respond most readily to moderate temperatures, similar to or slightly below those necessary for optimal growth, 14C at the lower threshold and 26C at the upper with 20C as the sweet spot in-between. It might be said that this represents the Holy Grail for environmental conditions in the stretch run, the goal being to ripen the fruit as quickly and efficiently as possible with optimal flavor and aromatics and balanced acid and alcohol. These are a lot of variables to align and every wine grower knows it is almost impossible to get all of these development curves to intersect at an ideal date on the calendar. Gladstones hedges his comments a bit by saying, “a range of optimum temperatures can be discerned, depending on grape variety and suggested ripening period optima for other climatic elements. His Table 3.1 on page 36 offers the suggested optimal climate averages for the final 30 days for a variety of wine styles.

As they have in California, I conclude from this that wine growers in warmer areas, mostly below the Mason-Dixon line, need to look to the hills to achieve the most effective diurnal effect for wine quality. As cooling occurs with higher latitude and elevation, warmth may be sought to bring the diurnal range to optimal range, for example, in the “banana belt” on the south and east shore of Seneca Lake. Gladstones formulates the same adage that grapes favor a cool site in a warm region and vice versa.”

If you need the temperature translation, 14C = 57F; 26C = 79F; and 20C = 68F.  As I said before, I don’t have the book yet and have not seen Table 3.1 that Mark references.  But also notice that Gladstones says that the temperature range differs among varieties.  I can tell you right now that we are not averaging these temperatures this year.  But other years, we can come close or be within the range.  For example, in 2010 at Perkins, if we harvested variety X on August 30, the average temperature was 29C = 83F.  Not too different.  Other years like 2009 and 2008 we are right in the higher end of that range.  If we had varieties that could be harvested at the end of September, then we are right in the optimal range.  There are a couple ways to get this done — one, choose varieties with later harvest dates (with this usually comes the added bonus of later budbreak).  Two, vine manipulation to delay harvest.  Work is currently being done in California at Fresno State by Sangliang Gu.  He has studies going that look at vine hedging and pruning at different times in the season to delay harvest, a technique called “Crop Forcing”.  He is finding some promising preliminary results in terms of berry chemical properties being enhanced, but also finding there is variation among varieties — some respond well and others do not.  This is ongoing work.  I started a similar study at Perkins in 2009 on ‘Neptune’, but only did one pruning time.  Since I did it early (May 1), the vines were able to catch up and harvest was not delayed much beyond a few days to a week.  Later pruning would likely push the harvest back later.  This would be a great area of study to pursue since it has the potential to significantly increase fruit quality.  The other part of this though is that sugar content may be sacrificed some, but the real issue is “should we be so focused on sugar content at the expense of pH, TA, malic and tartaric acid, K, etc.?”  Chaptalization is something we need to strongly consider as a tool in the winemaking arsenal.  As Mark states in his newsletter:

“As a wine grower, I tend not to fret over alcohol too much since careful chapitalization of wines is one of the least intrusive cellar interventions that can bring a wine into alcoholic balance, as has been done frequently in European wine regions prior to the recent effects of climate change. So as much as we tend to focus on brix as a parameter of ripeness, its importance is only that of a common indicator for other less well-defined criteria of fruit maturity (e.g. flavor, tannin, etc.).”

Something to think about as we move forward into the winemaking season.

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I have a trial of some hybrid grapes at OSU-OKC, Rubaiyat and Villard Blanc.  They are on two different trellis systems.  Last week, Becky went down and collected buds from both cultivars on both trellis systems.  The results were not surprising to me and were a welcome respite from the devastation we are experiencing at Perkins.  She did say, however, that there seems to be more dead canes on Villard Blanc, likely due to its high vigor.

Cultivar                Trellis System                Live Primary Buds/100

Rubaiyat              High Curtain                  66

Rubaiyat              VSP                                    67

Villard Blanc      High Curtain                  73

Villard Blanc      VSP                                    74

So, as you can see, the trellis system type made no difference in the amount of damage done by the cold.  Even though these numbers are decent for hybrids, vinifera types may have sustained considerable damage in the OKC area.  I have reported some results from the Edmond area previously where nearly all primary buds were killed on some vinifera grapes.

How would we prune these?  Simply compensate proportionally.  We will leave roughly 25% more buds than normal on VB and 35% on Rubaiyat.  So if we normally leave 50 buds per vine, this year we will leave 62-63 buds on VB and 67-68 buds on Rubaiyat.

Later this week we will be looking at buds of Chambourcin at the Bixby research station.  I am not expecting good news.

So you have cold damage to your grapevine buds.  You know that by going through the vineyard and randomly testing representative vines.  But now, it is time to start pruning.  Budbreak is just around the corner and you need to get it done before the vines get rolling.  So what do you need to know?

If the damage to your primary buds is 20% or less then you don’t need to do anything different.  I have also seen recommendations that lower that percentage to 10 or 15%; however, most grapevines will produce some crop on secondary buds, so those will act as compensation for the lost 20%.

If the primary bud damage is in the 20 to 80% range, then leave more buds in proportion to the amount that was lost due to the cold damage.  For example, if one normally leaves 40 buds on a vine and the damage is 70%, the new amount to leave is 68 buds (40 x .7 = 28, 28+40 = 68).

If the primary bud damage is greater than 80% then I recommend doing only minimal pruning.  Clean up material that is touching the ground, shorten canes so that you can work under the vines, top them (in case of VSP), but leave lots and lots of buds.  If you are surprised by the amount left, then you can always come back later and remove some.  But at the same time, don’t remove too many — if there is little or no crop, new growth may be extremely vigorous, leading to unwanted bull canes.  Leaving more competing growth will slow down that vigor some.

If your buds were really torched (multiple buds dead within the compound bud) then there may be wood damage as well to deal with.  This may mean the need to retrain cordons and trunks.  Choose new canes with good growth, but not excessive vigor, as replacements.  Wood damage is not always easy to see —  it can look like brown or black streaked or water-soaked.  Sometimes vines may break bud normally then crash when heat and other various stresses get to it.

The best advice I can give at this point is to know your vines and do your best with good, sound management strategies.

I just read a study published in the latest edition of the American Journal of Enology and Viticulture by Justin Morris and Gary Main, both from the University of Arkansas.  In their study they found that a 60+10 balanced pruning scheme increased the yield and clusters per vine when compared to a 30+10, but did not affect fruit composition.  So, better yield with the same quality.  When they left spurs to 3 nodes or 6 nodes they found no difference in yield; however, 3 node spurs were found to produce better soluble solids in the fruit and better vine vigor.  Resulting shoots should also be positioned (sometimes called combing) downward  to reduce vine vigor and lower fruit pH.  Vines were grown on either a GDC or SC (single curtain, aka high curtain) training system.

You can read the abstract here: http://ajevonline.org/cgi/content/abstract/61/4/445 or the entire article if you are a member of the society.

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