Vladimir G. Shutak - Grow the best blueberries

Vladimir G. Shutak
& Robert E. Gough

Between the two of us we have about 40 years experience in growing highbush blueberries in Rhode Island. We have read and published a lot of scientific papers about this plant. We have also killed a few dozen plants trying to improve their growth and production, but we believe that we have learned a few things in the process and would like to share them with you.

Would you like to grow blueberries in your own yard and enjoy fresh fruit for 8 to 10 weeks during the summer? You can, if you collect a few basic guidelines about location, soil, and culture. We will tell you how to do it all in this bulletin.

You know that there are a lot of different kinds of blueberries besides the highbush blueberry dryland, evergreen, mountain, rabbiteye, half-high, and low bush. We are going to talk about the highbush blueberry only the kind most common to commercial growers and the home gardener.

Highbush blueberry plants are easy to grow, relatively pestfree, and need little maintenance; they also fit very easily into most landscape plans. The plant has delicate white bell-shaped flowers in the spring, delicious fruit in the summer, bright crimson leaves in the fall, and red or yellow-colored branches in the winter.

Highbush blueberries can be grown in most areas of the United States; however, dont plant them in an area where winter temperatures frequently fall below 20F. Also, because they need winter chilling, dont plant blueberries in areas where there is not at least 800 hours (about 2 months) of temperatures below 40F. You can extend these limits somewhat by planting new cultivars especially developed for extreme northern and southern areas. In most cases these cultivars are crosses between highbush blueberry and rabbiteye for southern locations and low bush blueberry for northern locations.

You can extend the general temperature area limitations if you select a location within your area which is known to be warmer or cooler than the surrounding area this is called a microclimate.

For instance, if you have an area protected from the cold northern winds, it will be warmer than an exposed area. It will also reduce drying injury. You can create an area like this by providing a windbreak by planting trees or putting up a fence on the north side of the planting. Frequently, you can also take advantage of existing windbreaks provided by buildings yours or your neighbors.

Any structure even a driveway near your plants which absorbs and/or reflects heat, may help to maintain higher temperatures. If you are looking for a cooler area, select an exposed area with good air movement. A northern slope or an area which is shaded from the late afternoon sun (after 3:00 p.m.) will provide a cooler environment.

If you live in an area where late spring frosts are likely, locate the plants on a northern slope. This will delay the bloom in the spring and reduce chances of frost damage. A gentle slope is also recommended because it will provide better air drainage, help dry the air, and reduce fungus diseases. Do not plant in areas surrounded by buildings or dense stands of trees because both will cause poor air circulation.

For best production, plant your plants where they can receive 8 hours of sunlight per day. Too much shade results in spindly growth, reduces yield, and decreases the quality of the fruit.

Green Manure Crops

A green manure crop is usually a small grain crop that is tilled under before it matures. The decaying tops and roots provide organic matter and some nutrients to help build up the soil. This process increases soil aeration, water-holding capacity, and stimulates microbial activity in the soil.

Some of these grains grow best in summer and will not tolerate a frost. Others will survive the winter and are useful in preventing soil erosion during this time. Some commonly used green manure crops are listed below, along with their time and rate of seeding.

Seeding Rate

The best plants are grown on soil that has met three major requirements. First, it must be acid (sour) and fertile. Second, it should have a lot of organic matter; and third, it must have good water drainage. If you dont have this kind of soil, dont get discouraged. You can change the soil so that you do have good soil for blue-berries and we will tell you how to do it.

The best soil pH (acidity) for growing blueberries is between pH 4.5 and 5.6. This is also good for rhododendrons and azaleas. If your soil is higher than 5.6, you should add powdered sulfur. You may have to experiment a little with amounts for your soil conditions. In general, 24 pounds of sulfur for each 1,000 square feet should lower acidity by 1 full pH point. If your pH is too low, your soil is too sour, and limestone should be added to sweeten it. Again, the exact amount will depend upon your location, but about 150 pounds per 1,000 square feet will raise the pH by 1 pH point.

There are several home soil test kits you can buy. These generally will indicate soil pH and fertility. However, because most of these rely upon color tests, you may have a difficult time interpreting them. You will probably be better off having your soil tested through your local county extension agents office. There is usually only a modest charge for these services, and they will tell you how to take soil samples.

Blueberry soils should have a lot of organic matter. You can increase the level of organic material by adding compost, peat moss, leaves, straw, and other organic materials (except sewage sludge).

You must have good soil drainage with a water table no closer to the soil surface than 18 inches. A good way to test this yourself is simply to dig a hole about a foot deep and fill it with water. If the water disappears within about an hour and a half, the drainage is okay. If it doesnt youd better find another spot. But remember, swampy areas can be planted as a last resort, if you either install a costly system of drainage ditches or plant the bushes on small mounds as they grow naturally in swamps.

Preparing the soil for highbush blueberries means building up organic matter and adjusting the soil pH. The best way to start is to plant a green manure crop of buckwheat in the early summer prior to planting the blueberries the following spring. In late summer, measure the soil pH and adjust it to be between 4.5 and 5.0 by spreading either ground limestone (to raise the pH) or ground sulfur (to lower the pH)just before turning the buckwheat under. (Remember the formula: For loamy soil, add 24 pounds of sulfur per 1,000 square feet for each full pH point above 4.5. For sandy soil, decrease the rate to about 8 pounds per 1,000 square feet. For every full point you want to raise the pH, add about 150 pounds of limestone per 1,000 square feet.) In early September, till the area again, and plant a crop of winter rye. This will reduce soil loss from erosion during the winter months, as well as add additional organic matter. In early spring, turn under the winter rye and whatever other organic materials you can find rotted manure, compost, and peat moss and bring the soil to a fine texture by thorough harrowing or rototilling. Complete this and let the soil settle for at least 2 weeks before planting.