How to grow Grapefruit Tree in Australia

Where to plant

Grapefruit prefers cool winters and warm to hot, dry summers. Heat is what builds the sugar in the fruit, which is why grapefruit grown in cool summers stay sharp and sour. Plant it in full sun in your warmest spot, sheltered from cold wind and away from frost hollows.

Like all citrus it needs good drainage. It grows in a range of soils but does best in fertile, medium-textured soil of moderate depth, slightly acid, low in salt and well drained. On heavy or shallow soil, plant on a raised mound. Keep lawn and weeds out of the root zone and mulch, keeping the mulch clear of the trunk.

• South East Queensland, the Northern Rivers, Sydney and Perth: plant from March to September. Warm summers give sweet fruit.
• Adelaide: plant in March or April, or September or October. Hot, dry summers sweeten grapefruit well; water deeply through summer.
• Melbourne: marginal. Plant in October or November against the warmest wall. Cool summers keep the fruit sharp; Wheeny copes best.
• Canberra: very marginal. Plant in November on the warmest north-facing wall, with frost cloth for the first few winters. Wheeny copes best with cold.
• Hobart: our calendar marks Hobart as unsuitable, as summers lack the heat to sweeten the fruit. Grow a Meyer lemon instead.
• North Queensland and Darwin: plant in the dry season (May to September in North Queensland, May to August around Darwin) and water regularly through the dry. Tropical heat makes the fruit very sweet, though the skins often stay greenish.

Choosing a variety

Marsh is a seedless, white or yellow-fleshed grapefruit, less acid and more pleasant to eat when grown in warm conditions. Pink and red-fleshed types such as Ruby, Rio Red, Flame and Star Ruby are sweeter-looking and grow well in the tropics. Wheeny, an old Australian variety, is sharper but copes best with cold. Buy a grafted tree from an accredited nursery; dwarf trees on dwarfing rootstock suit pots and small gardens.

How to plant

1. Plant in autumn or spring in warm areas, after the last frost in cooler ones, or in the dry season in the tropics.
2. Water the tree in its pot well before planting.
3. Dig a hole wider than the pot but no deeper. On heavy or shallow soil, build a wide raised mound and plant into it.
4. Plant at the same depth as in the pot, with the graft union well above the soil.
5. Water in deeply and mulch, keeping the mulch 10 to 15 cm clear of the trunk.
6. Keep the soil moist while the tree establishes, watering at least weekly.

Watering and feeding

Water deeply rather than often, then let the top few centimetres dry before watering again. Established trees need regular deep watering through spring and summer, most of all from flowering until the fruit sets and through hot, dry spells. In the tropics, water through the dry season. Never leave the roots sitting in soggy soil.

Feed with a citrus fertiliser in late winter or early spring, again in summer and in early autumn, at the packet rate, spreading it around the edge of the canopy and watering it in. Avoid heavy feeding while the tree is in full flower.

Pruning and care through the year

• In the first couple of years, pick off most of the young fruit so the tree builds a strong frame. In the tropics, prune young trees to give them a good branch structure.
• Prune lightly: remove dead wood, which carries melanose, crossed branches, branches touching the ground and shoots from below the graft.
• Citrus gall wasp: cut out swollen galls on stems between April and June, or slice the top off each gall in mid to late winter.
• Bronze orange bugs: knock young bugs into a bucket of soapy water, wearing eye protection and gloves, as they squirt a liquid that burns.

Harvesting

In southern Australia grapefruit ripens through autumn and winter, and the fruit holds on the tree for months, getting sweeter the longer it stays. Pick as you need it, by twisting or cutting the stalk. Ripe fruit can still have some green on the rind, especially in warm areas.

In the tropics, do not leave ripe fruit on the tree. The NT Government notes that, unlike in the south, fruit left hanging in the Top End develops puffy skin, hollow centres and off flavours. In Darwin and Katherine the main crop is from mid February to the end of April. Grapefruit keeps for weeks in a cool place or the fridge.

Growing in pots

Choose a dwarf grapefruit on dwarfing rootstock and a pot at least 50 cm wide with good drainage holes. Use a premium potting mix suitable for citrus. Potted trees dry out and use up nutrients quickly, so water more often and feed lightly but regularly through the warm months. A pot also lets you move the tree to the warmest spot in cool areas.

Using it

Eat grapefruit halved with a spoon, segmented into salads, or juiced. Grapefruit and its juice can interact with more than 85 medicines, including some statins and some heart and blood pressure medicines, making them work too strongly. If you take regular medicines, ask your doctor or pharmacist whether grapefruit is safe for you.