Blueberries need soil at pH 4.5 to 5.5, which is more acid than anything else in a garden. Plant bushes about 4 weeks before your last frost, 5 feet apart, and expect a real crop in year three. Two varieties crop far better than one. Above pH 5.5 they cannot take up iron, whatever you feed them.
Soil pH is the whole story
Everything else about blueberries is ordinary. This one thing is not, and it is why most blueberry bushes disappoint.
Blueberries evolved on acid, peaty ground and take up iron only in a narrow, strongly acid band — roughly pH 4.5 to 5.5. Above about 5.5, iron in the soil becomes chemically unavailable to the plant no matter how much is present. The bush yellows, growth slows, and feeding it more makes no difference because supply was never the problem.
Most garden soil sits between pH 6.0 and 7.0. That is fine for vegetables and too alkaline for a blueberry, so a soil test is the first thing to do — before buying a bush, not after it fails.
To lower a bed's pH, elemental sulfur is the material and the timescale is months rather than weeks; how to lower soil pH has the rates by soil texture and the limits on a single application. Never lime near blueberries, and if you are correcting a bed for vegetables elsewhere, keep the lime calculator figures well away from this one.
Or sidestep it entirely with a container, which is what the next section is about and what most people should do.
Growing blueberries in containers
A pot lets you build exactly the soil the plant wants, which is a far easier problem than converting a bed and holding it there.
Pot size: at least 15 to 20 gallons for a mature bush, and a half barrel is ideal. A young plant can start in something smaller and be potted on. Allow at least 18 inches of depth.
Fill it with an ericaceous or acidic mix, not ordinary potting compost, which is buffered near neutral. A peat-based mix is the traditional answer and is naturally acid; where peat is a concern, composted bark and coir blends formulated for ericaceous plants do the same job. The difference between potting mix and garden soil matters here more than usual — garden soil in a blueberry pot brings its own pH with it and undoes the point.
Work out the volume with the potting soil calculator before buying, because a half barrel takes more mix than people expect.
Water with rainwater if you can. Tap water in hard-water areas is alkaline and slowly raises the pH of a container over a season. This is the commonest reason a container blueberry that started well declines in its second year.
Blueberry companion plants
Good neighbours, and why.
Strawberries share the acid-soil requirement almost exactly and are low enough not to compete for light, which makes them one of the few genuinely compatible underplantings. Thyme and other low evergreen aromatics tolerate acid ground and cover the soil surface without rooting deeply into the blueberry's shallow root zone.
Bad neighbours, and why.
Brassicas — cabbage, broccoli, kale — are the clearest exclusion, and the reason is pH rather than the plants themselves. Brassicas want a near-neutral soil and are usually grown in limed ground; the two requirements are incompatible in the same bed. The same logic rules out most vegetables.
The real rule for blueberries is that the companion has to want acid soil too. That is a much shorter list than the usual companion advice suggests, and it is why blueberries are usually grown in their own bed or their own pot.
Planting and spacing
5 feet between bushes, or about 8 feet between rows if you are planting more than one row. They grow larger than people expect — a mature highbush blueberry is a substantial shrub.
Plant about 4 weeks before your last frost, while dormant. Bare-root bushes go in early; container-grown plants are more forgiving and can go in through the season.
Set the bush at the depth it was growing, no deeper, and mulch generously. Blueberry roots are fine, shallow and fibrous, with no deep anchor, so a thick mulch of bark, pine needles or wood chips does real work here — holding moisture, keeping the surface cool, and acidifying very slightly as it breaks down.
Pollination and flowers
Blueberry flowers are small white or pink bells, appearing in spring before the leaves are fully out. Bumblebees work them far more effectively than honeybees, because the flower needs shaking to release pollen.
Plant two varieties. Most cultivars will set some fruit on their own and set much more heavily with a different variety of the same type nearby. The berries are bigger too. If you have space for two plants, two varieties beats two of the same.
Flowers appearing in the first year should be removed. Like strawberries, a young blueberry benefits from putting its first season into roots rather than fruit.
Watering and feeding
Water about 1.5 inches a week, and more in a container. Consistency matters more than volume — a blueberry that dries out during fruit development drops the crop.
Feed lightly, with an ericaceous fertilizer. Blueberries prefer nitrogen in ammonium form and tolerate nitrate-based fertilizers poorly, which is why an ordinary general-purpose feed can damage them. They are light feeders, and overfeeding causes more problems than underfeeding: a single light application in spring is enough.
Harvest
Fruit in year three for most bushes, with a full crop from year four or five, and then for decades.
Colour is not ripeness. A blueberry turns blue several days before it is ready and gains most of its sugar in that final window. The test is that a ripe berry detaches into your hand with a gentle roll of the thumb — if you have to pull, leave it. Pick over the bush every few days across a two to three week window.
Netting is the only reliable defence against birds, who judge ripeness better than most gardeners do.
Common problems
Yellow leaves with green veins. Iron chlorosis from insufficiently acid soil. Test and lower the pH; adding iron rarely works.
A container plant declining in its second year. Usually alkaline tap water slowly raising the mix's pH. Switch to rainwater, and refresh the top few inches of mix.
Few berries despite healthy growth. Either no pollination partner, or the plant is still too young. Both are fixed by patience and a second variety.
Drying out. Shallow fibrous roots and no deep anchor make blueberries unusually sensitive to drought, especially in pots. Mulch heavily and water consistently.
Blueberries suit the same acid ground as strawberries, and sit at the opposite end of the pH range from cabbage and the other brassicas.