Blueberries are among the most rewarding berries you can grow. They're hardy, barely troubled by pests, and they'll crop for many years. There's just one catch, and it's where most people come unstuck: blueberries want acidic soil, the kind you find in a bog or under conifers. In ordinary garden soil they sulk and give up after a year or two. Get this one thing right and the rest more or less takes care of itself.
Let's work through what matters, in order, from the soil to the container to picking in summer.
It all comes down to acidic soil
The cultivated blueberry (Vaccinium corymbosum) is a bog-bed plant in the heather family, a close relative of rhododendron and lingonberry. Its fine, shallow roots live in symbiosis with a soil fungus and only take up nutrients properly in acidic conditions. The ideal pH sits at 4.0 to 5.0. Most garden soils, by contrast, come in at 6.5 to 7.5, far too high.
If the soil holds too much lime, the plant can't take up iron even when the nutrients are right there. You'll see the result in the leaves.
A container is often the smartest choice
Instead of fighting your garden soil for years, turn the whole thing around: in a container you decide on the growing medium completely. On heavy clay or lime-rich soils, on a balcony or a terrace, this is the simplest and surest route to a heavy crop. Use a large pot of at least 40 to 60 litres, because the more medium there is, the steadier the pH and the moisture stay.
Choose a large pot
At least 40 litres, 60 is better, with drainage holes so water can't pool. Small pots dry out too fast and the roots overheat in summer.
Fill with acidic medium
Ericaceous (rhododendron) soil or bog-bed compost, ideally peat-free. Good peat-free mixes rely on composted bark, pine-needle litter and wood fibre, and they hold the pH down on their own.
Set the plant in the middle
Water the rootball thoroughly first, until no more air bubbles rise. Then set it deep enough that the ball is just covered with medium.
Mulch acidic and water in
Cover with a layer of pine-needle litter, bark mulch or conifer sawdust. That keeps things moist and keeps acidifying the soil. Water in well with rainwater.
If you'd rather plant in the ground
Set on planting the blueberry straight into a bed? Then make it a bog bed: dig a generous pit about a metre across and 40 cm deep and fill it completely with acidic medium. To stop the surrounding soil from creeping back in and raising the lime again, add a barrier down the sides, say a pond liner with holes in the base or a sunk-in root barrier. Then mulch heavily with pine-needle litter. Reckon on a bog bed like this needing more care than a container, because over the long run the pH always drifts back towards the native soil.
The wild bilberry (Vaccinium myrtillus) from the woods, by the way, is a different and much smaller species. It stains your mouth blue as you eat it and wants soil even more acidic still, but it's a good deal harder to grow in the garden. For the home garden, the large-fruited cultivated blueberry is the right pick.
Two varieties give you more
Why a neighbour pays off
Most cultivated blueberries are self-fertile, so they'll crop on their own. But stand two different varieties next to each other that flower at the same time (in May, roughly CW 18 to 21) and the flowers pollinate one another. The result: more berries, and each fruit turns out noticeably bigger.
Tough, heavy-cropping varieties have earned their place: 'Bluecrop' as the standard, the early 'Duke' and the late, wonderfully aromatic 'Elizabeth'. If you want to pick over several weeks, pair an early variety with a late one.
With blueberries it's not the care that makes the difference, it's the soil. Get that right and the rest almost looks after itself.
Watering: rainwater only if you can
Blueberries are shallow-rooted and must never dry out completely, especially in a container and while the fruit is forming in summer. But there's one important rule about the water itself.
Feeding without lime
Blueberries are light feeders. In spring, from about April on, give a dedicated rhododendron or berry feed that keeps the soil acidic and delivers nitrogen in a form the plant can handle. A second, smaller dose in early summer is plenty. Steer well clear of lime, ash and ordinary compost, however tempting that supposed extra helping of nutrients looks.
Pruning: not before the third year
For the first two years in the ground, just let the plant grow undisturbed. From the third or fourth year on, prune in late winter (roughly CW 6 to 9), before growth starts. Blueberries fruit on two- and three-year-old wood, so the aim is to keep the bush young and open: cut the oldest, dark shoots that barely crop any more right down to the base, and keep six to eight strong main stems depending on size. That lets light into the bush and keeps it steadily producing fresh, fruitful wood.
Picking in several passes
Picking runs from July to September (roughly CW 27 to 38), spread over several weeks depending on the variety. A berry is only truly ripe once it's blue all over with a light bloom and drops off at a gentle touch. Blue fruit that still holds fast usually needs a few more days, because blueberries hardly ripen any further once picked. So go over the bush every few days and take only the ripe berries.
Blueberries at a glance
- Acidic soilpH 4.0 to 5.0, or nothing happens. Use ericaceous (rhododendron) or bog-bed compost.
- Best in a containerAt least 40 to 60 litres of acidic medium, and you're in full control.
- Rainwater onlyHard tap water raises the pH and leads to chlorosis.
- Two varietiesCross-pollination brings more and bigger berries, say 'Bluecrop' plus 'Duke'.
- Feed sparinglyRhododendron feed in spring, never lime, ash or compost.
- Net at harvestPick from July to September and keep the berries safe from the birds.
Häufige Fragen
Can I just plant blueberries in ordinary garden soil?
Usually not. With a pH around 6.5 to 7.5, ordinary garden soil is far too alkaline. The plant gets chlorosis and struggles. Either make a bog bed with acidic medium, or plant straight into a container, which is a good deal easier.
How big does the container need to be?
At least 40 litres, 60 is better. The bigger the pot, the steadier the moisture and pH stay, and the less you have to water. In pots that are too small the medium dries out fast and the shallow roots overheat in summer.
Do I really need two varieties?
You don't have to, most varieties are self-fertile. But two different varieties that flower at the same time lift both the yield and the berry size noticeably. If you have the space, the second bush almost always pays off.
Why are my blueberry's leaves turning yellow?
Almost always because the soil isn't acidic enough. When the pH is too high the plant can't take up iron, and the leaves yellow between the green veins. Water with rainwater, mulch with pine-needle litter and re-acidify the medium rather than simply feeding more.
In short
Blueberries look demanding, but they aren't, once the acidic soil is right. Go for a container, fill it with acidic medium, water with rainwater and put two varieties together. After that all you need is patience, a net at harvest time and a spot in the sun. The rest comes on its own, a little more generous each year.
In Gartenkern you can set up the pH check, the rainwater sessions and the pruning as recurring tasks, and note which variety crops best for you. Come next summer you'll know exactly when your blueberry 'Bluecrop' first ripened and which container had the sunniest spot.
