One of the most frequently asked questions for me is how do I go about pruning? There are many considerations to ponder over when answering that. How old is the vineyard? What was last year's growing season like? What variety of grape? Was there any winter damage? What type of trellis system am I training my vines to? What crop load am I looking for? These questions and many more have to be considered.

The first thing I think of when it comes to pruning my vines is what was last season like? This will dictate how drastically the vines will be pruned. For instance, if you have been reading my previous news letters, you know that last year was a disaster in some ways. A horrific hail on Father's day stripped the vines of all their shoots from primary buds. This meant that growth was delayed until secondary buds could push. It also meant that much of the growth was weak or secondary buds didn't push at all, leaving shootless gaps in the cordon. Because of this, pruning this year will be to rejuvenate and en vigor the vines. This means drastic pruning. Removing whole cordons and starting over with the architecture of the vine in the case of cordon pruned vines. If last year had been a more typical year, I might be thinking of leaving more buds and controlling vigor. But this wasn't the case.

Next I take into consideration the growth habit of the variety and the type of trellis system I'm using. I train upright growing vines to the bottom trellis wire and either cordon and spur prune or cane prune depending upon the variety. Drooping varieties are trained to the top wire with either cane pruning or cordon and downward spur. Pruning with either growth habit is similar, just different wires.

I prune twice each spring. This is known as double pruning. At this time of the year I do my preliminary pruning. This is accomplished by removing all unwanted growth from the previous season. Those canes that are left will become spurs, canes, or cordons at the second pruning. I do not cut them back or tie them to the trellis wires. I leave them long and where they have attached to the trellis the previous season. This is a means of frost prevention. The buds at the tip of the canes will push first, leaving the basal buds more or less dormant longer. If a frost does occur, it will nip the tender shoots at the tip of the cane and it is these that I will remove after the danger of frost is over and the basal buds are beginning to swell. Tying these canes to the wires at this time cane force the basal buds to push before the threat of frost is over.

The second and final pruning is done after the tip buds have pushed into short shoots. This is the time where the canes I have left long are pruned back to spurs of two-three buds.

At this preliminary pruning you can evaluate winter damage to the buds. This is an important step to pruning. You want to have live primary buds that will produce a crop this year. Winter damage will dictate which canes you will save for this year's growth. Heavy damage will mean more drastic pruning and less crop load. You might find that the trunk has been damaged by low winter temperatures. In this case, you will have to cut the vine off at ground level and train a new shoot this year to replace the damaged trunk.

You have to protect the primary buds which contain the clusters of flowers that will eventually be your grapes. This is the trick to a successful vineyard under marginal conditions such as in the foothills of the Colorado Rockies. It is so frustrating to see your grapes succumb to low temperatures after they have pushed the buds and are quickly expanding the shoots and flower clusters. The secondary buds that push after the primary bud has been killed often produce only tiny, late maturing clusters or none at all.

Double pruning (as discussed above) is the traditional means to avoid killing spring frosts. Leaving the canes long at the first pruning and not doing the final pruning until the tip buds have begun growth suppresses the basal buds from pushing until after the threat of frost has passed. But this is not a cure-all to the problem.

Another alternative is to delay any pruning until late when the buds are beginning to push. This will do the same as double pruning but I find that it is too easy to damage swelling buds and emerging shoots that will be bearing the crop load if the complete job of pruning is left until this time. Double pruning allows one to remove the excess early, leaving those canes that will become the mainstay of fruiting shoots in a condition where it is easy to do the final pruning without damaging buds.

Buds become susceptible to killing temperatures from the time they begin to swell. This means that even the basal buds (when double pruning) can be killed if they have taken up water and the temps go low enough. I've had killing frosts at the vineyard as late as Memorial Day.

There are varietal differences when it comes to late frosts. Varieties like Foch swell early and are always in danger in the spring. Other varieties, like Landot 4511, bud out late and rarely are affected. The speed of growth is also a factor. Some varieties develop rapidly after bud break. These rapidly developing shoots are very tender, even with light frosts. Other varieties develop shoots slowly after bud break and tend to be less susceptible to light frosts. All succumb to freezes. The perfect variety would bud out late, after the frost danger has passed, then develop the shoots rapidly to mature the crop in a short season.

The key for me is to prevent the buds from taking up water and begin growing. This isn't an easy feat. Double pruning is only half of my strategy. I've experimented with several ideas over the years to prevent late frosts killing the primary buds of my vines. My first attempts were with the commercial frost treatments that are available. These are chemicals that are applied to the emerging leaves and shoots that prevent ice from forming on the tender tissue. None worked and some actually made the damage worse. The rapidly developing shoots in the spring are just too tender. They're like tomato plants when it comes to frost.

Finding a chemical which would delay budding in the spring until after the frost danger is over became one of my priorities. That's when I came across Sodium Alginate. I've performed experiments with sodium alginate as a frost avoidance treatment for the past three years. Each year I've varied the formulation and timing of application until I have come up with a treatment that seems to work satisfactorily in most years. This year will be the fourth year of experimentation and may prove to be the most critical.

I have experienced a very mild winter with unusually warm conditions. It's a long way to the optimum time for bud break and I'm sure there will be more than one killing frost before the danger has passed. As I write this, the temps are in the mid-60's but they are predicting snow and cold temps for the next few days. The trick is to delay bud break until after the first of May in my region. Not an easy task.

I combine double pruning with my sodium alginate frost avoidance treatment to delay bud burst as long as I can. After I've done the preliminary pruning, I apply the alginate to the buds that will eventually become my fruiting shoots during the growing season. The alginate pulls moisture from the buds and prevents them from swelling, thus not becoming susceptible to freezing temps by delaying bud burst until the frost danger is over. I pay special attention to the tip buds of the canes to see when they begin to swell. If it's an early, warm spring I will apply a second treatment when these begin to swell just to be sure that I suppress the swelling of the buds I want to bear fruit.

My Sodium Alginate Frost Avoidance Treatment® is still in the experimental mode. I'm constantly trying to improve it. Each year has brought different spring conditions that I have had to take into account. I am now setting up the experiments for this, the fourth year of alginate experimentation. A number of other growers are now experimenting with the Alginate treatment and providing me with comments on how the treatment behaves in other parts of the country and different environments from what I experience here. If you think that this might be an answer to your spring frost problems, you too can experiment with this treatment. Find out more by going to: Frost Avoidance Treatment.

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