erals produce laterals, and so on. Each year the lateral production on any individual cane decreases in diameter, or put in other words, the wood becomes progressively twiggy. It should be realized that as wood becomes smaller, fruit size decreases. This is why we detail prune to increase fruit size.
Assess the plant's overall vigor: is cane production adequate?
With this information under our belts we can address how to prune. There are really five basic steps to keep in mind when approaching a bush that is to be pruned.
- Locate the oldest canes and prune out one of every six canes. Thus, if the plant has twelve canes, remove two of the oldest.
- Prune out all the low branches that will never be picked and are a source for disease.
Armed with these basics, we can now deal with the different plant situations that arise. First, pruning young plantings has the primary objective of establishing the plant to obtain full production as soon as possible. Thus, during the first two years the goal is to remove flower buds. Some growers cut off as much as the top half of the plant. This is really quite drastic. Rubbing off flower buds would be sufficient. However, in a big operation it is usually less labor intensive to cut the top three to five inches off each cane, which will remove most flower buds. Any weak twiggy growth should also be removed.
- Detail prune: remove as much twiggy wood as time allows.
In year three, a small crop is possible without stunting the plant. Usually one to two pints per bush is the optimum and fruit should only be on strong wood. The fourth and fifth year twiggy growth must again be removed, as well as any lateral canes that have developed. Fruit production can be increased, but the amount is dependent on the number of new canes which were produced the preceding years: three to five canes per year is optimum. The blueberry planting should be in full production by the sixth year, though there are numerous variables which will influence this timing. The most important of these are proper pH and nutrition, water management, and the crop to cane production balance.
I have found it is also helpful to growers to discuss blueberry pruning strategies based on plant status. I do not believe there is a strategy for each variety, though any one variety may fall into one of the following categories most of the time. For example, the variety Blueray often has a spreading or open habit in which canes tend to bend down to the ground. Plants of this type must be thinned according to the one out of six rule. However, canes that are bent
(Continued on page 4)
Pruning Blueberries: Fact & Fiction
Gary Pavlis, Rutgers University
Reprinted from the Blueberry Bulletin, Vol. XXI, No. 21
New Jersey has approximately eight thousand acres of blueberries under cultivation and this is the primary crop for which I have extension responsibilities. Pruning continues to be little understood and poorly executed throughout the industry. In fact, it is rare to find two growers who prune the same. I would like to clear up a few misconceptions and try to outline a simple method of pruning blueberries.
The first place to start would be to discuss the importance of pruning. Growers often feel that pruning is of little value because the effects of the practice are not immediately apparent or dramatic. It should be noted that a well-known blueberry researcher, Phil Marucci, stated many years ago that there were a few factors which have greatly influenced the lack of increase in blueberry yield on a per acre basis over the last 30 years and pruning was the most significant factor.
More recent research has revealed that young canes are more efficient fruit producers than old canes. In fact, canes which are three to ten years old allocate greater than 50% of applied water and fertilizer to fruit production. By the time a cane reaches 20 years of age, only 25% is allocated to fruit (water and fertilizer cost the grower money, and there is no profit in the production of blueberry leaves!). Additional research compared the impact of three pruning types on yield and fruit size. Plants were: 1) regularly pruned in a moderate manner such that one out of every six canes was cut out; 2) heavily pruned by removing 40% of all canes every five years; 3) not pruned at all. The result was that the regular moderate pruning had the highest yield on the least number of canes. Research has also shown that as pruning increases, new cane production increases. These studies show us that young canes out-produce old canes, the removal of one out of six canes produces the right number of new canes, and the highest yield and fruit weight is produced with regular moderate pruning.
It is also important to understand how a blueberry plant grows. Each year, canes are initiated from the base of the plant. Each succeeding year, the cane produces laterals, lat-