How to Grow Blueberries: It Is All About Soil pH

Blueberries are not difficult. They are specific, in one way that no other common garden fruit is: they need soil at pH 4.5 to 5.5, which is far more acidic than most gardens have.

Get that right and they are close to trouble-free for twenty years. Get it wrong and the plant does not die quickly — it yellows, sulks, and slowly starves over three or four seasons.

Why pH decides everything

Blueberries are in the Ericaceae — the same family as rhododendrons, azaleas and heathers — and they evolved on acidic, peaty, low-nutrient ground.

At pH above roughly 5.5, iron in the soil becomes chemically unavailable to them, even though it is physically present. The plant cannot make chlorophyll, and you see it as yellow leaves with green veins, worst on the newest growth.

That is not a disease and it is not a feeding problem in the ordinary sense. Adding more fertiliser makes no difference; the pH has to come down.

Choosing varieties

Buy two varieties whose flowering overlaps. Most modern blueberries are partly self-fertile, so a single plant does crop — but cross-pollination gives visibly larger berries, more of them, and earlier ripening. Rabbiteye types in particular need a partner.

Spreading early, mid and late varieties across two or three plants also stretches the harvest from a glut into several weeks.

Planting

In the ground, if your pH allows: dig in a lot of composted pine bark, leaf mould, or ericaceous compost. Blueberry roots are fine and hair-like, sit in the top few inches, and have no root hairs — they need an open, damp, organic medium and they die in both drought and waterlogging.

Space highbush 4 to 5 feet apart, rabbiteye 6 feet.

In a pot, otherwise: a 15 to 20 inch container filled with ericaceous compost. This is the right answer for most gardens, not a compromise — it gives total control of pH, it makes netting easy, and you can move the pot.

Plant at the same depth it was in the nursery pot, and mulch immediately.

Mulch, water, feed

Mulch 2 to 3 inches deep with pine bark, pine needles or composted sawdust. It keeps the shallow roots cool and damp and helps hold the pH down. Keep it slightly clear of the stems.

Water consistently, especially from flowering through fruit development. Use rainwater if you can — hard tap water is alkaline and will gradually raise the pH of a container over a season or two, which is the most common slow failure of potted blueberries.

Feed in spring with an ericaceous fertiliser. These supply nitrogen as ammonium rather than nitrate, which is what blueberries can actually use, and usually include chelated iron.

Never apply lime, wood ash, mushroom compost, or general-purpose fertiliser. All of them raise pH.

Pruning

Do nothing for the first two years except remove damaged wood, and pinch off the flowers in year one so the plant builds roots instead of fruit.

Blueberries fruit best on two- to four-year-old wood. Older stems produce less and smaller berries. So from the third winter, while dormant:

1. Remove anything dead, damaged, crossing, or lying on the ground.
2. Cut about a quarter of the oldest stems — the thickest, darkest, most branched ones — right down to the base.
3. Thin any dense congestion in the centre for airflow.

That rotation means no stem is ever more than about four years old, and the bush stays productive indefinitely. It is the same principle as pruning currants, and it is far more effective than trimming the outside into a shape.

Birds

Birds will take the entire crop, and they will take it the day before you would have. Netting is not optional if you want fruit.

Use netting with a mesh small enough that birds cannot get through, held on a frame rather than draped on the bush — draped netting traps birds and they can be injured in it. Container plants are much easier to cover than a row.