Ask Mr. Smarty Plants

Vaccinium corymbosum (highbush blueberry) is native to New Hampshire and most cultivated blueberries are varieties or hybrids of the highbush blueberry. They are accustomed to wet to dry acid, rocky soils, and are extremely susceptible to chlorosis due to alkalinity in the soil.

Proper fertilizing of blueberries can be a little tricky. They evolved with shallow roots in low-nutrient acidic environments, and roots are easily burned by fertilizer. Yet, to get good fruit production demands fertilizer in late winter or early spring and again in late spring. One recommendation is for slow-release acid fertilizers such as those for rhododendrons and evergrees. Avoid concentrated fertilizers near the blueberries, and do not fertilize later than June. Another possibility is to use shredded hardwood bark or composted bark to mulch and shelter the roots from the cold and also to continue to add acidity to the soil, without disturbing the shallow roots for fertilizers.

Some of the stresses on blueberries that can cause reduction in production are insufficient sun, insufficient water or poor soil drainage. Young bushes need minimal trimming. Fruit is produced on second-year wood, so excessive pruning should be avoided. Most cultivars require cross-pollination with another cultivar. They are pollinated by bees, so avoid insecticides to encourage the natural bee population.

That's about all we could find that might be affecting the production of your highbush blueberry. Compare the conditions in which they are growing in your New Hampshire garden (approx. Zone 5a) and see what is wrong that you can fix.

Vaccinium corymbosum

Vaccinium corymbosum

Vaccinium corymbosum

Vaccinium corymbosum