Blueberry

About an inch of water a week, and never soggy

Give the bush roughly an inch of water a week through the growing season, wetting at least 50% of the ground under the canopy rather than a single spot at the trunk. Irrigate no more often than once every two days even in heat - go deeper, not more often. Keep the soil moist but never saturated. Blueberry roots are fine, shallow and fibrous with no root hairs, so they dry out fast in the top few inches and cannot chase water down; but the same shallow roots sit in whatever water does not drain. Watering daily encourages a shallow root system and invites root rot.

Mulch your blueberriesApr

Top up 3-4in of acidic mulch (pine bark sawdust or needles). Holds moisture and keeps the soil acidic they need.

Feed with ammonium sulfate as the buds begin to swell

At or just before bud swell, before the buds begin to break, band ammonium sulfate in a circle twelve to eighteen inches out from the crown, not against the stems. Give a first-year bush about one ounce and add another ounce each year until a mature bush is getting eight ounces annually. Do not feed a bush in its first four weeks in the ground. Blueberries take nitrogen up in the ammonium form, and ammonium sulfate is acidifying, so it feeds the bush while holding the soil near the pH 4.8 to 5.2 the roots need to work at all. Nitrate-form fertilizers have been shown to be toxic to blueberry and should be avoided.

⚠ Keep the band off the trunk and off surface roots; concentrated ammonium sulfate against the crown burns. If a soil test already puts you above pH 5.5 no amount of fertilizer fixes it, elemental sulfur applied a year ahead does. Continual ammonium sulfate can push pH below the desired range, so re-test rather than feeding blind.

Prune your blueberryMar

Remove the oldest gray canes and thin twiggy tips; keep 6-8 productive canes. Renewal keeps berries big and plants vigorous.

Spotted wing drosophila: trap as the first berries color

As soon as berries start to soften and show color, hang a vinegar trap in the shaded interior of the canopy and check it weekly for the small fly with a dark spot on each wing. Traps tell you the fly has arrived, they do not control it. If you find them, pick clean every few days and either seal culled fruit in a bag or bury it at least six inches deep; spinosad and pyrethrins are the home-garden sprays, effective for about seven to ten days. Unlike ordinary vinegar flies, this one has a saw-like ovipositor and cuts into sound, ripening fruit rather than waiting for damage, so the maggots are inside berries that look perfect on the bush. Sprays only kill adult flies - nothing you apply reaches the eggs or larvae already inside the fruit, which is why the trap has to go up before you have a problem.

⚠ Apply any spray in the evening after bees have finished working, and check the product label's pre-harvest interval before you pick - these go on fruit that is days from being eaten. Do not home compost infested berries; a backyard pile will not kill the larvae.

Mummy berry: first fungicide at green tip

At green tip, when the first leaf tissue is showing but no flowers are open, apply a labeled mummy berry fungicide such as a sterol inhibitor (for example fenbuconazole/Indar) and follow it with a second application 10 days later. Further applications can be made during bloom if wet weather continues and you saw shoot strikes. Check your state extension's current recommendations for products labeled in your area. Mummified berries lying on the ground push up little mushroom-like spore cups at bud break and fire ascospores at the only tissue that is vulnerable, the young expanding shoots. Those shoot strikes are what later produce the conidia that infect flowers, so stopping the shoot blight is most of the work of preventing mummified fruit.

⚠ Green tip is ahead of bloom, so no flowers are open and no bees are working the bush yet - keep any fungicide in ahead of bloom and apply at the label rate. Rake up and discard the old mummies, or bury them under two inches of soil or mulch; that removes the inoculum the spray is fighting. If you use overhead irrigation, run it in the early morning so leaves, flowers and fruit dry quickly.

Mummy berry: protect open flowers if you saw shoot strikes

If blighted shoots with gray fuzz appeared this spring, or the weather is wet, apply a fungicide at mid bloom and repeat every seven to ten days through petal fall. Fenbuconazole (Indar), metconazole (Quash), prothioconazole (Proline) and pyraclostrobin plus boscalid (Pristine) are the usual choices; Regalia tank-mixed with Serenade or Double Nickel is the organic route. Skip this entirely if you found no shoot strikes. Conidia from the shoot strikes are carried to the flower stigmas by the pollinators themselves, and the fungus then grows down into the fruit unseen until the berry mummifies at ripening. A flower is most susceptible the day it opens and stays vulnerable only about four days, which is why the window is bloom and not later.

⚠ Never put an insecticide on an open blueberry flower - the bees doing your pollinating are the same ones spreading this fungus. If you must apply a fungicide during bloom, spray at night after the bees have stopped working to keep them off wet residue.

Net the bushes as the fruit turns

As the first berries begin to color, drape plastic or cloth netting over the bushes or stretch it across a simple frame, and close it at the bottom so birds cannot walk in underneath. Leave it on until the last picking. Netting draped over the bushes or supported on a framework while the fruit is ripening is the only practical control for birds, which will strip a ripening bush faster than you will pick it.

⚠ Use netting with a tight mesh and keep it taut; loose, wide-mesh netting can entangle wildlife. Frame it off the foliage where you can, so you are not tearing fruit off every time you lift it.

Pick on a five to seven day round, and let them hang

Pick highbush every 5 to 7 days depending on how hot it is, and rabbiteye about every 10 days - rabbiteye flavor improves when it is picked less often. A berry that is fully blue has usually not finished sweetening; give it a few more days and roll it off with your thumb rather than pulling. Take overripe and damaged berries off the bush as you go, and seal or bury them rather than dropping them underneath. Blueberries keep sweetening after they turn blue, so picking the moment the skin colors costs you flavor; but fruit left too long goes soft and becomes the breeding site that builds a spotted wing drosophila population for the rest of your harvest. The interval is a compromise between those two.