A second key to success is soil. Blueberries demand soil quite different from that enjoyed by most other garden plants. For blueberries to thrive, the soil must be well aerated, moist, very high in humus, and—most important of all—very acidic. These conditions are not, however, difficult to create. Start by doing a soil test, then acidifying it, if necessary to a pH of between 4 and 5.5 by mixing in sulfur, a natural mineral, the season before you plant your blueberries. The amount to use depends on your soil's initial pH and your soil's texture, and ranges from one to seven pounds per hundred square feet. If you indicate on your soil test that you will be planting blueberries, most testing services will tell you the amount of sulfur to use. Mix it into the top six inches of soil across the area of the entire mature root zone.
Now you're ready to plant. Set lowbush blueberries two feet apart, highbush blueberries six feet apart, and rabbiteyes fifteen feet apart. Enrich the soil in each planting hole by mixing in a bucketful of composted leaves or pine needles, which will help maintain acidity and provide a long-lasting source of humus for optimum nutrition, aeration, and moisture. Set each plant slightly deeper than it stood in its pot or nursery row.
Right after planting, spread a three-inch layer of organic mulch over the ground. This mulch will thwart weeds and keep the roots cool and moist (most of a blueberry's root system lies within inches of the soil surface). Straw, shredded leaves, pine needles, or wood chips are good choices for mulch, but I prefer well-aged sawdust, but never from wood treated with a preservative.
Once the plants are settled into their new home, give them a thorough watering. Provide them with one to two inches of water weekly—from rain, a hose, or drip irrigation system during the growing season. Another way to measure water needs is to give them one-half to one gallon per square foot of root zone each week.
Pruning + Feeding
Your blueberries won't need any pruning at all for their first three years. (Remove fruit buds the first two years after planting to allow the bush to establish itself.) After that, annual late winter pruning rids the plant of old wood, stimulating and making way for young, fruitful branches. Pruning also removes crowded, misplaced, or unproductive stems and, by removing some fruit buds, lets those that remain develop into larger and sweeter berries.
Prune lowbush blueberries by cutting the plants completely to the ground every second or third year. (Commercial growers accomplish this by burning over the entire field, but don't try this in your backyard.) The bushes do not bear the season immediately following pruning, so prune a different half or third of the planting every second or third year to keep yourself in nonstop berries. With highbush varieties, stems remain productive for about six years, so the first step in pruning these bushes is to remove six-year-old stems either to the ground or to low, vigorous side shoots. Then thin out crowded or weak stems. Prune rabbiteye blueberries just like highbush blueberries, only less.
Blueberries do not like rich soil, but fertilizer may be needed if annual growth is less than a foot, or four inches for lowbush varieties. Organic fertilizers are ideal for blueberries because they are less likely to burn the plants' tender roots and because they supply nitrogen in a form blueberries use best. Use seed meals, such as soybean or alfalfa meal, at the rate of 1/4 to 2 cups per plant depending on plant size. Every two or three years I do a soil test and spread sulfur if I need to lower the pH. And I replenish mulch yearly.
Birds + Harvesting
Birds love blueberries as much as we humans do and will strip bushes of most, if not all, of your harvest without even waiting for the berries to ripen. The only truly effective way to deter them is by sealing your bushes with bird-proof netting. I construct a temporary, walk-in cage of metal conduit and plastic pipe over my planting just as the berries begin to ripen. If you choose to drape netting over the shrubs, be careful to gather it tightly at the base of each plant so winged marauders can't find their way inside.
Blueberries actually don't reach their full flavor and aroma until a few days after they turn blue. If you want the sweetest berries of all—ones that will really outshine those on market shelves—tickle the blue bunches of berries. Only the dead ripe ones will fall off into your hand.
We eat lots of blueberries in summer but could not possibly consume fresh the production of our fourteen bushes. Some backyard growers dry extra berries in a dehydrator or make jams and pies from them. Our answer is to freeze the excess about 40 quarts each season by spreading the berries out on pans in the freezer for about 1 hour, then packing them into plastic freezer bags. That way we can have fresh, bush-ripened berries all year long.
Never Say Never
If your soil is naturally alkaline, as it is in many areas of the West, you might think that you are unable to grow acid-loving blueberries. Nonsense! All you need to do is bring the right soil to your blueberry patch. Here's how to create your own miniature acid-loving zone:
1. For each bush you wish to plant, excavate a hole two feet deep and six feet around and fill it with a mix of equal proportions of peat moss and sand.
2. Keep the bed mulched with aged sawdust (which is acidic) or other organic material, and fertilize annually with a balanced organic fertilizer.
3. If you irrigate and your water also is alkaline—in other words, if you have hard water, acidify it first with two teaspoons of vinegar per gallon.
The Right Varieties For Your Climate
Before choosing a variety, you need to determine which of the four types of blueberries is best suited to your region. All four types require a period of prolonged chilling to set flowers, but some need less time and cold than others. Planting different varieties of the same type will give you bigger berries and a larger yield.
1. Highbush blueberries (Vaccinium corymbosum), the type usually found in supermarkets, are so named because the large, dark berries are borne on bushes that grow six to eight feet high. Northern highbush blueberries grow best in USDA Plant Hardiness zones 4-7. Popular northern varieties include Blueray, Bluecrop, Jersey, and Patriot. Southern highbush types, which thrive in zones 7-10, include Cape Fear, Gulfcoast, O'Neal, and Blue Ridge (V. pallidium). With a low chilling requirement, southern types bear well even in Florida.
2. Lowbush blueberries (V. angustifolium, Zone 3-6) are super-hardy, making them great for gardeners who live where winter temperatures regularly plummet below zeo. In contrast to tall high-bush varieties, ground-hugging low-bush stems grow a mere six to eighteen inches high as they spread by underground runners. The berries themselves are small and sweet, with a powdery, sky blue bloom. A few varieties of lowbush blueberries such as 'Top Hat' have been selected and bred, but wild seedlings simply called low bush blueberries are what are mostly available at nurseries. This means that fruit flavor and appearance, and plant size will vary from one seedling to the next.
3. Half-high blueberries were born when growers married the large berry size of high-bush blueberries to the cold-hardiness of low-bush. The plants don't grow as tall as high-bush, nor do they spread by underground runners. Varieties include Friendship, Polaris, Northland, and North-blue.
4. Rabbiteye blueberries (V. ashei, Zones 7 to 9) give southern gardeners another option besides southern high-bush. Typically smaller than high-bush berries, they ripen later in the season. Newer varieties, such as Bonita and Climax, have delectable flavor and cross-pollinate each other well. Rabbiteye bushes can grow ten or more feet tall, and the plants are less finicky about their soil than other kinds of blueberries.