by Sanne Kure-Jensen
“A well-maintained blueberry bush should outlive the grower,” said David Handley, vegetable and small fruit specialist with UMaine Extension.
For peak production, Handley recommended blueberry bushes be maintained in a “state of continual adolescence.” Handley says the best way to maintain optimal blueberry production is with routine winter pruning.
When pruning acres of blueberries every year, stick to the basics and spend no more than five to 10 minutes per plant.
Handley recommends pruning when bushes are completely dormant, depending on the season and location.
Many growers make a second pass in late winter or early spring to remove winter-injured wood.
Pruning in fall before full dormancy may increase winter injury and cause plants to flower earlier next spring, risking frost damage to flowers and fruit.
Handley recommends these pruning steps for blueberry bushes:
1. Remove dead, diseased and damaged branches, cutting close to a healthy joint. In years one to three, this is the only pruning needed.
2. Thereafter, prune each bush to maintain six to 12 canes. The canes should range from one to six years old. The most productive canes will be those two to four years old. Remove canes with the most small twigs or branches at their tops. Keep the center open so the canes do not shade each other.
3. Remove one to four of the oldest canes (six-plus years) near the ground using a bevel cut. Exception: Growers should cut canes 12-18” from the ground to encourage re-growth for plants such as ‘Patriot’ that do not produce new canes freely. The older stems will have peeling bark, twiggy tops and the thickest canes. Keep a few strong 1-year-old canes as future fruiting wood.
4. Remove weak, thin, one-year-old shoots, less the 4 inches long from the branches.
5. Keep shoots that are 6 in. or longer with healthy fruit buds.
6. Handley recommended growers remove 50-70 percent of the total fruit buds during the pruning process. This will prevent bushes from developing biennial bearing habits.
7. Remove chocolate brown or black, winter-injured twigs.
8. Remove pendant wood — branches that aim down or into the picking aisles.
If you miss several years of pruning or take over an abandoned blueberry farm, there are options for keeping those overgrown plants, rather than replacing them. The chainsaw approach means cutting all of the canes to 12-18 in. and letting them regenerate. There will be very little fruit production for about three years. Regenerative pruning means removing a quarter to a third of the major canes each year for three years. There will be berries each year, with improved yield as the plant is rejuvenated.
Handley referred to these general pruning guidelines:
1. Sanitize tools between plants using a 5 percent bleach solution or alcohol “swish and rinse.”
2. Maintain a shrub height of 4 to 6 ft. for highbush blueberries and 2.5 to 3.5 ft. for mid-size bushes.
3. Remove crossed or rubbing branches
4. Keep tools sharp. Handley recommends sharpening tools at the start of each session and again every hour or two in the field.