Tips to Increase Yields and Improve Harvesting
I begin my annual fall-to-winter blueberry pruning about the time of our first hard fall frost as plants begin to go dormant. First I remove “droopers” — long, willowy stems hanging over into row middles.
While doing so this past year, I noted that most of them began just below high basal stem removal cuts made several years ago. Others originated higher up on stems that came from such old high-cut “stumps.” In the photo, note that the top pruning cut was a stem removal cut made years ago. The bottom cut was made just this past fall and was made properly: within 2 inches of the ground, and removed both drooping canes in one low cut.
Why We Make High Basal Cuts
I have seen these basal stem removal cuts made several inches above the ground and plant crown in many older blueberry plantings in this region, along with my 36-year-old plantings. The reasons growers made these high basal cuts can be summarized:
- 1. Scientists such as Dr. Gary Pavlis’ Extension research in New Jersey on blueberry pruning showed the need for stem removal cuts to be made within 2 inches of the ground and crown. This knowledge was unknown many years ago and is proven to result in crown rejuvenation producing strong, upright, vigorous growth of new stems. We knew there are records of old blueberry plantings five or more decades old, but we did not realize maintaining profitable yields with larger-size berries in old plantings requires maintaining crown vigor and stem renewal using near-ground stem cuts and old stumps removal.
From the standpoint of worker comfort and less back pain from pruning, workers found it was much easier to remove old stems higher up, which sure beat bending way over to cut stems off close to the ground, especially if the boss was not watching!
- Many growers did not have long-handled, heavy, large-size lopping pruners with jaws that could reach around older, large-diameter stems.
- If large-size lopping pruners were found with jaws that could open wide enough, some workers did not have the strength to make the cuts in such large diameter, hardwood stems and old stumps.
- Using hand saws to remove those large diameter old stems, especially from old stumps, was just too slow; many growers could not finish pruning each year.
- The lithium-ion battery had not been invented many years ago, nor commercialized for use in lightweight, hand-held reciprocating power saws with pruning-specific cutting blades.
What Happens When You Make High Basal Cuts?
The results of many years of too-high basal stem removal cuts: Growers may have too many weak, willowy, drooping stems that make difficult mowing, harvest, and field work. Such willowy, drooping stems bear fruit near the ground, easily missed in picking, and can be mashed under-foot.
The cure is to cut off those old high-pruned stumps and excess stems (eight stems per plant is optimum), making the cuts 2 inches or closer to the ground. Two successful options exist to bring back your older plantings to profitable yields with larger size berries:
1. Using knee pads and a small, hand-held reciprocating power saw with pruning blade or a small chain saw, remove all the old stumps and attached stems on up to one half of each plant. On the other plant half, little pruning is done that winter, so that you will obtain a fruit harvest from that portion of the plant, uninterrupted. New, strong, straight stems will arise from the cut portion of the plant and are thinned to three or four of the strongest on that one-half of plant, then annually pruned to keep just those three or four stems.
When these new stems begin fruiting in profusion by the third year on that half of the plant, the other half of the plant is removed in the same fashion. Over the course of four to six years you have completely renewed this planting, while still obtaining a harvest each year, weather permitting of course.
2. A second option used successfully involves a small chain saw along with those good knee pads to get down and cut off the entire old plants 2 inches or closer to the ground level, realizing there will be no harvests for the following two years. The next growing season after these whole-plant removal cuts, six to eight of the strongest, biggest new stems are selected and kept. All others are removed annually for the first two years, again close to the ground.
By the third year from cutting off plants, good harvests resume and are maintained until these first-selected stems are five years old. Three of them can be removed in the fifth year, three more in the sixth year, as young replacement stems kept in year three now take their place. After the sixth-year harvest, annual winter pruning should remove the two to three oldest stems annually, always close to the ground, so keep those knee pads handy!
Some growers using this method choose to cut off only a few rows of the old plants each year, until the entire planting has been renewed over time. If your older planting is healthy, but has a lot of high stumps and/or too many stems, and declining yields of smaller berries, proper renewal pruning is vital to the profitability and the longevity of your planting, and is so much less expensive than replacing the old field with a new planting!
Remember, it is never too early to begin this process on older fields during this current winter pruning season.