St Lawrence Nurseries
325 State Hwy 345
Potsdam, NY 13676
|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 but do not disturb roots.
5) Mulch annually with an acid material like pine needles
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. Naturally-occuring highbush blueberry bogs 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.”
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, Polaris, St.Cloud and Superior 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 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.
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. 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.
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.
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 allow for head clearance.
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, where it produces a cluster
of small cup-like mushrooms the following Spring. 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
The best way to assure top quality fruit is to delay picking until several
days to a week after the fruit has turned fully blue. This waiting period
allows the pulp to go from mealy (as in many supermarket berries) to soft,
juicy and flavorful. Waiting for this extra flavor and juiciness to develop
will not significantly reduce the shelf life of the berries, especially
since you are not a commercial grower shipping them across the country.
Both you and your customers will be amazed at how much better fully-ripened
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 plant is a fully
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.