Cold returns for a few days

The cold has returned to Wisconsin.   Last night we got down to about 26F.    Some buds may have already seen some damage.  At least foch and Lacrescent had already approached full swell.


Below is a nice table that shows critical temperatures for bud survival.  The table below was originally on the Michigan State University Extension web site.    That link is now dead.   (I will gladly link to another source if someone has it.)



CRITICAL TEMPERATURES FOR GRAPES

Growth Stage	Description	No Damage	10% Kill	50% Kill	90% Kill
Dormant	Bud not swollen.		Varies with conditions.
First Swell	Early swell, bud brown, no color.		13	7	-3
Full Swell	Late Swell, swollen bud looks pink.		26	21	10
Bud Burst	Leaves at tip of bud separate.	30	28	25	16
First Leaf	One leaf out at 90° to the stem.	30	28.5	27	21
Second Leaf	Two leaves out, 90° to the stem.	30	29	28	22
Third Leaf	Three leaves out, 90° to the stem.		28		26
Fourth Leaf	Four leaves out at 90° to the stem.		28		27

(The above table and photos originally from Michigan State University Extension) 

I believe the 10% and 90% kill numbers originally came from Rutgers and refers to Wine grapes.   The 50% kill numbers come from Washington State University and refer to concord grapes.  I do not know the accuracy of the numbers with respect to cold hardy vines such as French Hybrids, University of Minnesota cultivars, or Swenson cultivars.   It is interesting none the less.  

Not yet guys!!!

Unpruned lacrescent bud swell on March 21, 2012

It's March 21 and the temperature was over 80F in the vineyard today.   We are seeing significant bud swell on lacrescent and foch.   Cooler weather is expected, so hopefully the vines will hold off a few more weeks.   If we see bud break in the next week or two, the risk of a hard frost is still quite high.

Slow down guys.

Too Warm?

Weather Underground Forecast for March 18- March 21 (observation from Sat. night 11:40 pm)

This is crazy weather.  The forecast high for tomorrow (Sunday, March 18) is 81 F.   If I wasn't a grape farmer, this would be awesome, but this could be really devastating for grapes.   If we have bud break in the next few weeks, the chance of a hard frost between bud break and mid-May is quite likely.   This could mean a severe hit to yields this year.   On the other hand, if we do have an early bud break, and no frost, we may have one of the best grape years in memory.  Unfortunately the former is more likely than the latter.

I spent a few hours pruning Prairie star today.   I saw some bud swell compared to last weekend.   Pruning cuts from last weekend were actively dripping.   The vines look great, but the a few frosty nights would be great to slow things down.  

If I didn't have such limited opportunities to prune, I would delay pruning as long as possible.   Delayed pruning is beneficial for delaying bud break since buds towards the ends of canes break first.    Based on the extended forecast, I may not have all of my vines pruned before bud break.  Hopefully slightly cooler temperatures forecast for next weekend will slow things down just enough.

Pruning has begun

Before

After

We began pruning the vines on Saturday, March 10.   Above are some marquette vines.   We are doing most of the vineyard as VSP (vertical shoot position).   We leave about 25-30 buds per vine.  

The vines look good.   I've seen very little winter damage as expected.   The next couple of weeks are going to be crazy warm for March.   I wouldn't be surprised if bud swell or bud break could occur a month early.   Not something I hope for.   We are bound to get a frost between now and May, and a bud break in April will surely mean bud/shoot damage.

We will see what happens.