How to Grow Citrus in Pots in Australia

Lemons, limes, mandarins, oranges and kumquats for balconies, courtyards and cold climates

Citrus are one of the most rewarding fruits you can grow in a pot. A single well-fed tree gives you fragrant blossom, glossy evergreen leaves and a steady supply of fruit, all from a container you can stand by the back door. Because the roots are confined, a potted citrus stays smaller and comes into fruit quickly, which makes it perfect for balconies, courtyards, small backyards and rented homes where you cannot plant in the ground.

Pots also unlock citrus for cold areas. Citrus dislike hard frost, so in cooler districts the ability to wheel a pot into a sheltered spot, against a warm wall, into a greenhouse or indoors over winter is a real advantage. Get the pot size, the mix, the watering and the feeding right and a container citrus will crop happily for many years. Use the helper below to size your pot and set up a feeding routine, then read on for variety picks and care.

Choosing a Tree and Dwarf Rootstock

Almost all citrus sold in Australia are grafted, with the fruiting variety joined onto the roots of a tougher, more disease-resistant plant. For pots, ask specifically for a tree on a dwarfing rootstock. The classic choice is Flying Dragon (a contorted form of Poncirus trifoliata), which holds a tree to roughly half the size of a standard one, keeps it in scale for a container, and often brings it into fruit a year or two sooner. Standard Trifoliata rootstock is also commonly used and suits pots well in cooler areas.

Buy a healthy, well-grown two to three year old grafted tree from a reputable nursery rather than a tiny seedling. Seed-grown citrus take many years to fruit and are not true to type, so a grafted, named variety is always the better buy for a pot.

The best types for containers are the compact, reliable croppers:

• Lemon: Meyer (the most pot-friendly and cold-tolerant), and Eureka or Lisbon for a true sharp lemon.
• Lime: Tahitian (Bearss) lime, the fragrant kaffir or makrut lime grown for its leaves, and the slow, compact Australian finger lime.
• Mandarin: Imperial and Emperor are productive and easy to peel.
• Orange: Washington Navel and Valencia, choosing compact or dwarf-grafted forms.
• Kumquat: one of the very best citrus for pots, naturally small, heavily ornamental and easy to crop.

Pot, Mix and Position

Use a pot with plenty of drainage holes and stand it on pot feet so excess water can escape and the base does not sit in a puddle. Fill with a premium free-draining potting mix or a dedicated citrus and fruit mix. Never use garden soil or heavy clay in a pot, as it compacts, holds water and suffocates the roots.

Position is everything. Citrus crop best in full sun, a minimum of six to eight hours of direct light a day. Pick the warmest, brightest, most sheltered spot you have and protect young trees from strong wind and frost. A sunny north-facing wall that radiates warmth is ideal, especially in cooler districts.

Watering

Watering is the single biggest cause of problems with potted citrus, in both directions. The aim is consistent moisture without waterlogging. Water when the top 3 to 5 cm of mix feels dry, then soak the pot until water runs freely from the drainage holes. In peak summer heat a pot may need watering every day. Mulch the surface of the mix to slow evaporation and keep the roots cool.

Just as important, never leave the pot standing in a saucer of water. Constant wet feet lead to root rot, which is often the real reason behind sudden yellowing and leaf drop. Young trees need the most consistent moisture while they establish their roots.

Feeding

Citrus are gross feeders, and potted trees are hungrier still because every watering washes nutrients out of the mix. Feed little and often through the growing season with a citrus-specific fertiliser that contains trace elements, especially magnesium, iron and zinc. A simple routine is a complete citrus food in early spring, again in early summer and again in early autumn, topped up with a monthly liquid feed of seaweed or fish emulsion. Ease right off through winter when the tree is barely growing.

Match the strength to the tree. Young trees do best on lighter, more frequent diluted feeds, while established trees can take the full rate at each seasonal point. Always water before and after feeding so the roots are never fed when dry.

Pruning and Fruit

Citrus need only light pruning. Shape the tree to keep it open and balanced, remove any dead or crossing branches, and snip back the odd wayward shoot. The one job not to skip is removing rootstock suckers, any vigorous shoots that appear from below the graft union. They are not your fruiting variety and will sap the tree, so rub or cut them off as soon as you see them.

On a very young tree it pays to remove the fruit in the first year and to thin a heavy set in the next year or two. It feels harsh, but it lets the tree put its energy into building a strong framework rather than stalling under a load of fruit it is too small to carry.

Common Problems

Yellow leaves

Yellowing is the most common citrus complaint and the cause is written in the pattern:

• Over-watering or poor drainage: overall dull yellowing with soggy mix. Let the pot dry out more between waterings and check the drainage holes are clear.
• Nitrogen deficiency: even, pale yellowing across older leaves first. Feed with a complete citrus fertiliser.
• Magnesium deficiency: yellowing between the veins on older leaves, with a green inverted V at the base. Common in pots, and corrected with a citrus food containing magnesium or a watering of Epsom salts.
• Iron deficiency: yellowing on the newest leaves while the veins stay green. Usually linked to cold, wet or alkaline conditions, and helped by a chelated iron drench.
• Cold stress: general yellowing and leaf drop after cold snaps. Move the pot to shelter over winter.

Citrus gall wasp

Citrus gall wasp is a major Australian pest. The larvae cause woody swellings, or galls, along the stems. Cut out and bin or solarise any galls before the adults emerge in spring (roughly late winter to early spring), so you break the cycle before they lay again. Yellow sticky traps placed in spring help monitor and reduce the adults. Avoid over-feeding with nitrogen late in the season, as soft growth is more attractive to the wasp.

Citrus leafminer

Leafminer leaves silvery, squiggly trails inside new leaves, which then curl. It is mostly cosmetic. Tolerate it on established trees and protect only the new flushes on young trees, with horticultural oil applied to the soft new growth.

Scale, sooty mould and aphids

Scale insects suck sap and excrete honeydew, which grows a black sooty mould on the leaves. Aphids cluster on new shoots. Treat all three with a thorough spray of horticultural oil, which smothers scale and clears the way for the mould to wash off.

Collar and root rot

Soggy mix and wet feet cause collar and root rot, seen as gum oozing at the base and a tree in slow decline. Prevention is the cure: free-draining mix, pot feet, and never standing the pot in water.

Winter Care in Cold Areas

This is where pots earn their keep. In cold, frost-prone districts move the pots before the first hard frost to a sheltered, sunny position, against a warm wall, into a greenhouse, or indoors next to a bright window. Reduce watering over winter, since a cool, barely growing tree needs far less, and stop feeding altogether until spring. Protect the canopy from frost with horticultural fleece if a cold night threatens, then move the tree back into the open as the weather warms.

Best Citrus Varieties for Pots in Australia

Frequently Asked Questions

See also: Mandarins in the Plant Library