Soil acidity is the key to abundant blueberries

Lee’s blueberries (photo by Lee Reich)

My 16 blueberry plants keep me in blueberries year-‘round, so I’m not planting any this year. But you are, or should be. The bushes are attractive in every season, with white blossoms in spring, foliage that looks spry all summer and turns crimson-red in fall and stems that shade to red in winter. The bushes are almost pest-free. And the berries are healthful and delicious.

All you would-be blueberry-planters out there: Pay attention to the soil for your plants, about which I’m going to offer advice. Too many people plunk a blueberry bush into a hole dug in their lawn and then wonder about the lack of berries. Poor growth, that’s why. The plants bear fruit on one-year-old stems. If shoots grow only a few inches one year, there’s little room on which to hang berries the following year.

Taking a cue from wild blueberries, here’s what the bushes need, soilwise: acidity (pH 4 to 5.5), organic matter, relatively low fertility, moisture, air and no competition from weeds. For starters, check the soil pH with either a home testing kit or by taking a sample to a Cooperative Extension office or soil-testing laboratory. If soil is not sufficiently acidic, add sulfur – preferably pelletized sulfur for ease of handling – three-quarters of a pound of sulfur per 100 square feet in sandy soils, or three times this amount in heavier soils, for each pH unit that the soil is above 4.5. Contrary to popular myth, adding oak leaves or pine needles will not do the trick.

Spread sulfur over the ground as far as the eventual spread of the roots, which is about three feet in all directions. Then dump a bucketful of peat moss right where you plan to dig each hole. Dig the hole deep and twice as wide as needed to get the plant in the ground, mixing the peat moss with the soil. Peat moss provides a long-lasting source of organic matter, which also helps with aeration and water-retention. Finally, plant and water.

Wait, you’re not finished yet. Right after planting, spread some organic mulch, such as wood shavings, leaves or pine needles, a couple of inches deep and as wide a spread as the roots. Mulch keeps the soil moist and further enriches the ground with organic matter as its lower layers decompose.
Ongoing soil care for blueberry bushes is simple and necessary: mostly food and drink. Assuage the bushes’ thirst with, barring rain, three-quarters of a gallon of water per week for each square-foot spread of the roots. Satisfy their hunger by spreading a high-nitrogen fertilizer late each fall. I use an organic fertilizer, such as soybean or alfalfa meal, at the rate of 1.5 pounds over every hundred square feet of root spread. These fertilizers offer nitrogen throughout the growing season in a form that blueberries can use.

Periodically recheck the soil pH and add more sulfur, if needed. Replenish the mulch each fall, laying the new mulch right on top of the old mulch.

For the future – harvest of first berries should begin within a couple of years – think about birds. Are you going to share? Are they going to share? I opt not to share, enclosing my whole planting in netting, to create a walk-in “blueberry temple.” Turning inward – not introspectively, but to the greenhouse – I see aphids getting a foothold. Their populations soared a few weeks ago, as young and old feasted on aging celery and arugula plants beginning to send up seedstalks.

My first counterattack was to cut down or dig up these old plants and whisk them to the compost pile before too many insects dropped off to take up residence on smaller plants and seedlings. Not that there weren’t plenty of stragglers fattening up on younger plants.

My tack with the stragglers has been to set my watering wand on “fan spray” and blast the plants with water. Most aphids that get knocked off plants don’t return. I spray on mornings of sunny days so that leaves dry relatively quickly, limiting potential disease problems. The temporary increase in humidity might increase the likelihood of aphids’ getting fungal diseases, to which they are very susceptible.

Of less effect are the ladybugs that I periodically introduce into the greenhouse, in large part because I don’t have enough of them. They used to enter my home in large numbers via leaks around an old south-facing window and nearby crack in the wall. I’d merely vacuum them up as they clustered on the windowpane and shake the contents of the hand-held vacuum among plants in the greenhouse late in the day. That window and the wall crack have been repaired, so few ladybugs end up indoors.

I’m considering making a hole in the wall to let the ladybugs indoors again and hanging a ladybug live trap (available commercially or made from online plans at https://www.ars.usda.gov/is/br/lbeetle/001030.trap.pdf) right near the hole. Thus far, though, cleanup and water sprays have kept aphids under control, and plants are growing well. Once transplanted outdoors, aphid problems vanish because of the weather and natural predators.

 

Any gardening questions? E-mail them to me at [email protected] and I’ll try answering them directly or in this column. Come visit my garden at www.leereich.com/blog.

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