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St Lawrence Nurseries
325 State Hwy 345
Potsdam, NY 13676
315-265-6739

BLUEBERRIES


 
 
Checklist for growing blueberries:

1) Do not plant too deeply; plant in surface layers of the soil.
2) Provide adequate water after planting.
3) Maintain soil pH at 3.5 - 4.5.
4) Keep free of weeds.
5) Mulch annually with an acid material  like pine needles or sawdust.
6) Cultivate only lightly. 
7) Prune mature plants annually, in early spring before flowering.
8) Fence to keep out mice, rabbits, deer, etc.
9) Irrigate (drip or overhead)) during fruit enlargement and ripening.

Site and Soils

Blueberries like a well-drained, highly acid soil with access to plenty of water.  Highbush blueberry bogs in nature are wet enough to make your sneakers squish while you are picking berries, but each bush is “high and dry” on a hummock of higher ground composed of soil, sphagnum moss and organic matter. Abundant water, especially important during fruit enlargment, is readily available, but the plant roots are not drowning.  At the other end of the spectrum, the wild lowbush blueberry grows in sandy, often dry soils.  Where the sand is close to the water table, berries flourish annually, but in the drier uplands, good lowbush berry seasons depend on local rainfall. Insufficent rain will result in berries that shrivel or fail to reach full size during the fruiting season.  Wild berries grow only where the soils are very acid, with a pH of 3.5 to 5.0.  A highly acid bog or upland dune patch is annually endowed with leaves or needles from the acid-loving plants growing there, which add organic matter and maintain soil acidity.

Mimicking nature gives the best results for blueberry growing.  Find a spot that is well protected from late Spring frosts, acidify the soil with heaps of acid mulch every year, provide access to plenty of water, and “voila!”...you will have blueberries.  Surprisingly, the backfill sand around the foundation of your recently-built house can be a good spot, and blueberry plants make an attractive “edible ornamental.”
 

Spacing

Be sure to space your plants far enough apart so that you will be able to pick the fruit without having to squeeze between plants. Simply brushing by the fully-loaded branches of a blueberry bush that is heavy with ripe fruit will cause many berries to fall off.  Patriot, Bluegold, Chippewa, Friendship and Polaris plants will spread to a  width of 4 feet. They should be spaced 4-5 feet apart in the row. Northland is a particularly spreading bush at 5 feet width, so a 5-6 foot spacing would be warranted for these. Plants like Northblue, St. Cloud and Northcountry, which mature at about 2 ft. tall and  spread to about 4 ft. wide, should be spaced 4 feet apart in the row, and low growing plants like Northsky and Putte (3 ft. spread) need only 3 feet between plants. Be sure to leave a full 6-8 feet between the rows to allow freedom of movement when picking.
 

Planting

The root systems of blueberry plants are comprised of a mass of tiny rootlets ending in millions of root hairs. These sensitive roots need oxygen. They thrive in loose soil with no competing weeds, and a heavy mulch of acid organic matter. They spread out widely, often suckering to send up new canes, and remain fairly close to the soil surface. We’re reminded of the fellow who just couldn’t get his blueberry plants to grow.  Conditions were perfect: soil, mulch, pH, the works. He then showed us how he laboriously cultivated deeply around each plant, unknowingly eliminating a good percentage of its roots!

Blueberries should be planted in a way that allows the roots to spread out, in shallow holes. The roots will be just under the surface, with the canes poking above the ground. The soil should be pressed firmly around each plant and watered well. Heavy soils are not good for blueberry roots.
 

Mulching and Soil pH

Mulch, mulch, mulch!  Create an environment where only blueberries like to grow.  Most common garden weeds can be discouraged by an annual 6-8 inch layer of naturally acid mulch around the plants and in between the rows.  We use pine needles, which are readily available from the pine woods nearby, and ground bark from a nearby sawmill.  Pine or oak sawdust, oak leaves, peat, or any other naturally acid mulch will work. Yellowing of leaves on young blueberry plants may mean that your soil is not acid enough. Blueberries do not require high nutrient levels, but they do require an acid environment to take advantage of the nutrients that exist in the soil. The soil for blueberries should be at a pH of 3.5-5.0.  Take time to test the pH of your soil. It is an easy-to-do test that can be obtained from your local Cooperative Extension or farm supply store. (See Soils.)  If your soil  has a pH higher than 5.0 and does not respond to acid mulching, you  can use elemental sulfur to acidify it more rapidly.  However, sulfur should be used sparingly, for it can burn or even kill young plants.  Sprinkle  1 tablespoon  of sulfur lightly around each plant and let it dissolve into the ground at its own pace, or mix thoroughly with mulch and then mulch the plants. When amending the soil with sulfur, give the plants enough time to start showing the effect.  It can take several weeks or longer for the leaves to regain their healthy green color.  Once the plants are growing well and no more yellowing is occuring, natural acid mulches should be enough to maintain the desired pH.
 

Fertilizer

Blueberries are not heavy feeders.  In fact, recent research shows that, contrary to previous recommendations, they need hardly any additional nitrogen during the growing/fruiting season. Go easy on NPK, and if you are an organic grower, use only compost and acid mulches. Do not fertilize after June 15.
 

Irrigation

While blueberries cannot tolerate wet feet, they need access to plenty of water. This is critically important during the period of fruit enlargement, which begins just after fruit set and ends just before ripening. Drip irrigation is one inexpensive way to insure adequate moisture to the fine hairlike blueberry roots. Overhead irrigation such as a lawn sprinkler will also work, but uses considerably more water.
 

Netting for birds

Want to attract birds to your property?  Plant a blueberry patch!  We guarantee that you will soon earn a reputation among your feathered friends as the #1 hangout of the neighborhood.  You may not think birds are a problem at first.  We didn’t.  But then we noticed that the blueberries that were “almost ripe” yesterday never got any riper.  (Actually, the birds were eating them as they got ripe.)  It is highly advisable to net your plants whether  you have a large commercial planting or a small berry patch.  One-inch nylon mesh works well. It should be put up during early fruit production and taken down just afterward.  Never leave up the net year-round.  You will want to erect some sort of support (we use tall posts with wires strung across the tops) to hold up the net.  Make it tall enough to clear people's heads when they walk around inside the net picking fruit, and remember; it will droop down some. Also, rabbits love to nibble on blueberry shoots, and will often nibble through bird netting to get to them.  This leaves gaping holes through which the birds gladly follow the rabbits. We solved this by surrounding our patch with a permanent, 4-foot tall 1" X 2" welded wire fence, dug in well at the soil level, the top of which forms a convenient attachment point for our overhead net during fruit season.  Bird netting is relatively inexpensive and will easily pay for itself in one year.  With proper care, the netting should last 20 years or more. See the Source Table for sources of netting.
 

Pests and Disease

Healthy blueberry plants are bothered very little by pests and disease. If you have problems with leaf-eating caterpillars,  bt (Bacillus thuringiensis) should take care of them, although the “finger pinch” method is often just as effective.  Mummyberry can be a problem. This is a disease which results when infected berries fall to the ground, allowing the fungus to overwinter and, as soon as wet weather comes the following Spring, produce a cluster of small cup-like mushrooms. These mushrooms “shoot” their spores up onto the plant, which infects first the developing leaf buds, then the flowers of the plant, thus starting the cycle all over again.  Because it is a fungus, mummyberry is worse in wet years. It helps to keep all drop berries picked up, especially directly under the plant. You can rake the old mulch and debris out from under the bushes in the Fall and replace with new mulch. Lightly hoeing the mulch under the bushes in early Spring (March) will help disturb sprouting mushrooms. After pruning, remove all pruned-off wood from the blueberry patch to prevent the cycling of disease.

Picking Fruit

Blueberry plants live to be 40-60 years old. Once they are mature (five to eight years old,) it’s a good idea to renew the plants annually by pruning, removing all dead canes and excess canes.  You should remove one to three of the oldest canes each year, pruning them to the base of the plant at the soil level.  In a vigorously growing adult, all canes should have been renewed every 6 years.  In the far north where growth is slower, this cycle can be extended to 8 or 9 years for complete renewal.  Do not begin removing canes until your plant is a fully grown adult.
 

Pruning

Blueberry plants live to be 40-60 years old. Once they are mature (five to eight years old), it's a good idea to renew the plants annually by pruning: removing all dead canes and excess canes. You should remove one to three of the oldest canes each year, pruning them to the base of the plant at the soil level. In a vigorously growing adult, the rule of thumb is that all canes should have been renewed every 6 years. In the far north where growth is slower, this cycle can be extended to 8 or 9 years for complete renewal. Do not begin removing canes until your plants are fully grown adults.
 

Hardening off

Do not encourage late season blueberry growth by fertilizing, mulching, or foliar feeding after mid-June. Fertilizer or foliar feeding sprays applied later than this in northern areas can cause plants to grow during the time that they would normally be slowing down and hardening off for winter. The result is that the plants are “caught with their pants down” by the arrival of cold weather, resulting in winter injury. Mulch may have the same effect if applied after June 15. The best times of the year to mulch are: after the ground has cooled and the plants are fully dormant in the Fall, and/or after pruning but before flowering in the Spring. You can also help your blueberry plants escape winter injury by making sure the surrounding soil is as moist as possible before Fall freeze-up. Plants dessicate during winter cold snaps. Occasional thaws allow plants to bring up badly needed water into dry stems and twigs. Thus, a plant’s ability to survive winter is closely associated with water availability to the roots. In young plants whose roots are not developed, watering in the late fall, after leaf drop but before the ground freezes, helps plants to counter the dessicating influences of winter.