How to grow Blueberry in Australia

Where to plant

Choose a sunny spot with shelter from strong wind. In hot inland areas and in South East Queensland, some protection from the hottest afternoon sun in summer helps. Blueberries have shallow, fine roots, with almost all of them in the top 20 to 30 cm of soil, so they need soil that stays moist but never waterlogged.

The soil must be acid. Most Australian garden soils are closer to neutral, and limy or alkaline soils are common in South Australia, parts of Victoria and the Perth coastal plain. Test the pH with a cheap kit before you plant. If your soil is heavy clay, alkaline or badly drained, grow blueberries in a raised mound or a large pot of acid mix instead of fighting the soil.

• Aim for pH 4.5 to 5.5. Leaves that turn yellow between green veins usually mean the pH is too high.
• To lower pH, dig garden sulphur into the top 20 cm of soil several months before planting, following the packet rate, then test again. It works slowly, so start early.
• Never add lime, dolomite or mushroom compost to a blueberry bed, as all three raise the pH.
• Raised mounds of acid mix with plenty of compost give the roots the drainage they need in wet climates.
• Rainwater is best. In some areas tap water is alkaline and slowly pushes the pH up, so check it once a year.

Choosing a variety

Blueberries need a certain number of cool winter hours (chill hours, below about 7°C) to flower well. Pick the type that matches your winter.

Blueberries are not suited to North Queensland or the Top End, where winters are too warm and the wet season brings root rot.

How to plant

1. Plant in winter, when potted plants are easy to find and the weather is mild.
2. Prepare the bed or mound with plenty of compost and acid mix, and check the pH is 4.5 to 5.5.
3. Dig a hole about twice the size of the pot and plant at the same depth the plant sat in its pot.
4. Water in well with rainwater if you have it.
5. Mulch 5 to 10 cm deep with pine bark or pine needles, keeping it just clear of the stems.
6. In the first year, pick off the flowers so the plant puts its energy into roots and growth.

Watering and feeding

Blueberries have little water in reserve because their roots are so shallow, so water little and often rather than in big, rare soaks. Commercial growers in northern New South Wales apply about 25 to 40 mm of water a week in the growing season. For a home bush, that means a good soak two or three times a week in warm weather, more in heatwaves and every day for pots in summer. Too much water is as harmful as too little, as soggy soil brings on root rot.

Feed with a fertiliser made for azaleas and camellias in spring and again in summer, at the packet rate. These supply nitrogen in the ammonium form blueberries prefer. Go easy: too much fertiliser gives leafy growth and fewer flowers, and it can burn the fine roots. Top up the mulch each year.

Pruning and care through the year

• Years 1 to 3: only remove dead, damaged and weak twiggy growth.
• Mature bushes: prune in winter. Cut a few of the oldest, thickest canes off at the base each year, so the bush keeps a mix of young, middle-aged and old stems. Young canes carry the best fruit.
• Net the bushes as the first berries start to colour, before birds find them.
• In Queensland and New South Wales, watch for fruit fly in ripening berries and pick promptly.
• Check the pH each autumn and add a little sulphur if it has crept above 5.5.

Harvesting

Berries are ripe when they are fully blue with a silvery bloom and come away into your hand with no green or red at the stem. They do not ripen any further once picked, so leave them a few days after they turn blue for the best flavour. Berries on a bush ripen over several weeks, so pick every few days.

Low-chill types in South East Queensland ripen from late winter through spring. In cooler areas the main crop comes in summer. A mature bush can give several kilograms of fruit a season.

Growing in pots

Pots are often the easiest way to grow blueberries, because you control the soil completely. Start with a pot at least 30 to 40 cm wide and deep for a young plant, and move up to 45 to 50 cm as it grows. Compact varieties such as Sunshine Blue suit pots best.

Use a premium potting mix made for azaleas and camellias, which is already acid. Water with rainwater where you can, as potted plants dry out fast and tap water can raise the pH in the small volume of mix. Repot or refresh the mix every two to three years, and feed lightly through the warm months with an azalea and camellia fertiliser.

Propagation

Blueberries are usually bought as named varieties, since seed does not come true. Home gardeners can root new plants by mound layering: bury the base of a few low stems in acid mix and leave them for 6 to 9 months until they form roots, then cut them away and pot them up.