Keeping Blueberries Happy In Containers

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Sunshine and Slightly Acid Soil

In a recent entry, I mentioned that, because of my resident deer herd, I grow my blueberries in containers. This sparked several good questions, so I thought I’d provide a bit more detail for those of you who want to try it. However, if you want a lot of fruit and have plenty of room, I’d suggest growing highbush blueberries. These big, strapping creatures can top 8 feet in height, and thrive in full sun. Their roots are shallow and wide-spreading, so they appreciate good garden soil, well amended with compost.

To keep the humus level high, renew blueberry bed mulch each spring and fall. Add any combination of aged manure, mature compost, rotted leaves, and well rotted sawdust or finely ground bark to improve soil and help smother weeds. Compost is especially valuable, since it strengthens and sweetens fruit flavor and provides most of the nourishment these sturdy plants need.

Just Enough, Never Too Much

Give blueberries full sun and good air circulation, as well as a dedicated bed free of root competition from nearby trees. Blueberries thrive near water but don’t tolerate waterlogged soil. They grow best in open-textured, well-drained loam, with plenty of humus (organic matter). They prefer acid soils with a pH between 4.5 and 5.5, which fortunately is quite typical throughout the maritime Northwest.

While consistent moisture is important to blueberry production, excess fertilizer and water dilutes that subtle, tart-sweet flavor. If you use irrigation, make sure it delivers two inches of water a week to new shrubs, and 1 inch a week to established bushes. Don’t overfeed, but use a combination of compost mulch and a slow-release organic fertilizer to enjoy the fullest-flavored fruit. Fertilizers that will mildly increase soil acidity include cottonseed meal, feather meal, and fertilizer blends made for rhododendrons and azaleas.

A Blueberry Edible Hedge

Blueberries can be planted as close as 3 feet apart to form solid hedgerows, which also makes them slightly easier to net so birds can’t capture the entire crop. You can also space them 6-8 feet apart as free-standing individual specimens. If planted in rows, allow  about 8 feet between the rows, especially if you use a large mower to keep a grassy path well shorn (though better paths could be made from wood chips or shavings).

If you’ve got ample space, consider growing Chandler, a tall (5-7 feet) shrub that produces huge, plump berries with great flavor. Blueray (4-6 feet) is an old-time blueberry with excellent vigor and fine flavor. Highbush blueberries bear up to eight quarts of fruit a year. For a long and productive season, grow some early, mid- and late fruiters. If you plan to make pies and freeze extra berries, plant three or more bushes per person, otherwise two each should do.

Light Pruning Makes For Stronger Plants

Blueberry shrubs need little pruning beyond the removal of dead, broken, or weak stems. In spring, trim off any aging, unproductive branches, making room for sturdy new branches to develop. In late winter, trim back productive branches by 25% to encourage new fruit bearing shoots to form.

Where space is limited or deer are rampant, grow your blueberries in containers. Mine are on a deck almost 20 feet above the ground, and so far, no deer has managed to reach them. Compact blueberry varieties will be happiest in large containers filled with slightly acidic, moisture-retentive soil.

Potting Soil For Acid Lovers

Since bagged potting mixes are pH neutral, I blend my own slightly acid garden soil with aged dairy manure and compost. You can also use Booster Blend, a mix produced by Seattle’s Cedar Grove, which combines compost with composted dairy manure.

As I have probably made abundantly clear in previous posts, I never use peat, which is destructively strip-mined and devoid of nutritional value. Dairy manure is an excellent replacement, especially from dairies that don’t use Bovine Growth Hormone or routine doses of antibiotics and steroids. My favorite source for pit-washed dairy manure is Moo Doo For You (see below), but most Agricultural Extension services offer manure Hotlines for sourcing local manures.

Unlike peat, aged dairy manure makes an excellent soil amendment and top dressing. So does coir fiber, a byproduct of the coconut industry. Wiry and tough, yet fine textured, coir breaks down slowly, providing soil nutrients and improving soil texture for several years (or more).

Big Pot, Big Harvest

Give blueberries large containers to accommodate their  wide, questing roots. Plant new blueberries in pots that hold at least 5 gallons. After two years, pot them up into half-barrels, where they can remain indefinitely. To keep them happy, topdress with aged compost each spring and fall, and feed moderately from spring through late summer as outlined below.

Good container candidates include Tophat, the smallest blueberry bush, and Northsky, which tastes like wild berries. Northblue and Northcountry are both 2-footers that thrive in containers for many years. If the container is large enough (think half-barrel), so will my favorite, Sunshine Blue, an evergreen blueberry with silvery blue foliage that looks lovely all year round.

Those in Western Washington can get beautiful aged, dairy manure from:

Moo Doo For You
Mark Vukich
(206) 271-6490
(253) 939-0627

This entry was posted in composting, fall/winter crops, Garden Prep, Growing Berry Crops, Nutrition, Pets & Pests In The Garden, Pruning, Sustainable Gardening, Sustainable Living and tagged , . Bookmark the permalink.

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