Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
I think that my favorite time of year is blueberry season. I love blueberries. I stock up on them, baking with some and freezing the rest. If I had enough space, I would grow them myself.
What are Blueberries?
What we call blueberries are flowering shrubs that are native to North America. There are similar flowering shrubs that are native to Europe, but their berries are slightly different and called bilberries (Vaccinium myrtillus). Blueberry shrubs are also related to cranberries (V. macrocarpon) and huckleberries (V. membranaceum). There are four types of blueberries that are commonly grown.
Highbush blueberries (V. corymbosum) are by far the most popular blueberries with home gardeners. They are called highbush because they are upright shrubs that grow 5 to 6 feet tall and wide. They are a manmade shrub, developed in the early 20th century from wild blueberries. They have large berries. They are hardy from zone 4 to zone 7.
These shrubs (V. angustifolium) are the original shrubs known to the indigenous peoples of North America. They are prostrate bushes and have small berries. Their flavor is more intense than highbush blueberries. These are the berries found in canned blueberries and jams. They are hardy from zone 3 to zone 7.
This is a hybrid (V. corymbosum x V. angustifolium) between the highbush and lowbush blueberries. The shrubs are about 3 feet tall and have the larger fruit of the highbush cultivars with the cold tolerance of the lowbush shrubs. They are hardy from zone 3 to zone 7.
Rabbiteye blueberries (V. virgatum) are native to the southern United States. The shrubs are large, 15 feet tall and 10 feet wide. They are popular in warmer areas because they are not bothered by pests. The berries are large. You will need to plant more than one variety of rabbiteye for successful pollination. They are hardy from zone 5 to zone 10.
How to Plant Blueberries
The best time to plant blueberries is in the very early spring. You should get a soil test done before planting your shrubs. Blueberries are related to rhododendrons and azaleas and like them need acidic soil. Unless you are living in the middle of a pine forest, most likely you will need to amend your soil to achieve the recommended pH of 4.5 to 5.2. If the soil is too sweet, your shrubs will be iron deficient resulting in leaves that are yellow. Eventually, it will kill them.
There are two ways of decreasing the pH of your soil. You can spread ground sulphur at a rate of 2 to 3 ounces per shrub on the soil and work it into the soil. Using this method, it will take about a year for your soil to reach the appropriate pH. A quicker way is to dig a hole that is wider than the container your shrubs are in and mix peat moss into the soil you have removed from the hole. Place the root ball in the hole and backfill with the soil and peat moss mixture. This will lower the pH of the soil that the roots will grow into.
For best pollination and large harvests of berries, you should plant more than one shrub. Plant them 4 to 5 feet apart, closer if you are planning to make a hedge.
How to Grow Blueberries
Choose a spot that gets full sun which is a minimum 6 to 8 hours of sunlight each day. Blueberries can tolerate a little shade, but grow best and bear more fruit if they are grown in full sun. It is best to mulch them. Their roots are shallow and dry out easily. A little trick I have seen used is to mulch the shrubs with evergreen needles which are naturally acidic. This keeps the soil at the correct pH level.
An alternative is to fertilize your shrubs using fertilizer that is formulated for rhododendrons and azaleas. Hold off on fertilizing your newly planted shrubs for about a month. After that, you can fertilize in the early spring to help them get going and again in the late spring as they are blooming. Be sure to water well after fertilizing. The roots are very sensitive. They can be burned by fertilizer.
Keep an eye on your local rainfall. Blueberries like to be moist. They need 1 -2 inches of water each week.
And don’t forget to purchase bird netting. Birds love blueberries and can easily strip your shrubs of berries before you have a chance to harvest any. Cover your shrubs with netting as soon as the berries start to appear.
How to Prune Blueberries
After about 6 years, you will notice that your shrubs aren’t producing as many berries. It’s time to start pruning. Growth that is 6 years old or older does not fruit well. It is the new growth that produce the most berries. For best results, prune your shrubs every year starting when they are 5 years old.
Pruning Highbush, Half-high and Rabbiteye Blueberries
Shrubs should be pruned in late winter or very early spring. Start by removing any dead or broken branches, branches that are hanging low to the ground and branches that are crowded in the center of your shrub. Then remove any branches that are 6 years old.
Pruning Lowbush Blueberries
Lowbush blueberries are cut to the ground every year in the late winter or very early spring beginning when they are 5 years old. Shrubs that have been pruned to the ground will not bear fruit that year, so for continuous production in your blueberry patch, prune half of your shrubs the first year and then the other half the second year or prune 1/3 of your shrubs each year for three years so that the unpruned shrubs will continue to bear fruit for you.
How to Harvest and Store Blueberries
When you purchase your shrubs from the nursery, you will be getting 1 to 2 year old plants. They don’t bear many berries when they are that small so it is best to not allow them to make berries the first year that you plant them. You can accomplish this by removing any flowers that appear. Instead, allow them that year to establish their root systems and start to grow and fill out.
Starting the second year, you can begin to harvest your berries. The harvest may not be as large as you like. Don't worry. As the shrubs grow each year, so will your harvest.
The berries start out green, then ripen to a reddish purple before finally turning the familiar dark purple/blue. Don’t pick them as soon as they are ripe. Wait a few days. Berries that are fully ripe should be easy to pick, literally falling off into your hand.
Blueberries will stay fresh for up to one week in your refrigerator or you can freeze them for up to 10 months.
© 2019 Caren White