We will continue pruning Edelweiss this week. We are wondering if we will ever finish! Weather permitting, we will apply herbicide and fungicide.

Let’s consider spraying for a minute. We can’t spray when the wind is blowing at more than 5 miles per hour. We can’t spray when the vineyard is too wet because the heavy equipment will tear up the turf. We don’t want to spray if rain is predicted within 24 hours because whatever we spray could be washed off before it can do any good. So, we have a very narrow window to get the job done. This is why it seems like we are always spraying. We will plan to spray but then the weather doesn’t line up exactly right and we have to put spraying back on the schedule for the following week.

We experienced a cold snap Saturday night. Fortunately, it got down to about 32°F but not low enough to damage buds that are tender right now. We were lucky this time.  Based on past weather patterns, the date that represents the 90% confidence level that we won’t have any more freezing weather for the season is May 11. So, we will be on pins and needles about the possibility of a hard frost for a while longer.

iowa vineyard, short pruning, machine pruningWe didn’t have long to wait. On Sunday night, April 28-29, the temperatures dropped to 29°F. The vineyards at Tassel Ridge seemed to do well indicating that low temperatures there were a bit higher. There was some outer leaf damage, but the center of the buds seemed to be firm. At Meadowcreek just north of Oskaloosa, there were frosted buds of all varieties. Probably 30% of the buds were actually killed off. At Maple Woods on the east side of Oskaloosa, there is a small amount of damage in the Sabrevois at the top of the hill. However, the same variety at the bottom of the hill down near the creek, lost all primary buds that had opened up. The small emerging buds that had not opened up seemed OK. Almost all of the St. Pepin and Brianna buds in the north block were frozen off. At Newport Lane about three miles due north of Maple Woods, the damage was limited to exterior leaves.

Grapevines have been coping with cold temperatures in the spring after budding-out for millennia and they have adapted by having primary, secondary, and tertiary buds. The primary buds are the first to leaf out and are the most susceptible to cold snaps in the spring. They also produce the heaviest grape load. Secondary buds leaf out a little later and they will also produce some fruit but not as much as the primary buds will. So, not all is lost although we expect production to be diminished. Finally, tertiary buds come last but they are not fruitful.

So far, we have machine pruned all of our 38,000 vines. We have short pruned just over half of our vines. We will be pushing hard to get the rest of the short pruning done before we have to change priorities and start planting new vines in Mid-May. We are about four weeks later than usual because of very cold weather at the beginning of March that prevented us from getting started.