Your citrus care guide Right now is the perfect time to show your citrus trees some love
As the harvest comes to an end, and flowers start appearing ahead of the next crop, it’s an important time on the citrus calendar. There’s training and pruning to be done, feeding and watering, and potential pests to deal with. It’s also time to think abo
PRUNE FOR SIZE AND SHAPE
You can get away with never pruning a citrus tree; it doesn’t need to be pruned in order to fruit better. The only issue is, it will keep getting bigger until one day, in a fit of frenzy, you feel compelled to take to it with a saw and give it an almighty chop back. You can often get away with that, too, but it severely stresses the tree.
Think of the leaves as solar panels. When you remove all the branches and foliage, you take away the tree’s ability to produce the energy it needs to grow, and force it to rely solely on stored energy until it recovers (and there’s a chance it won’t).
Furthermore, removal of the canopy exposes the remaining branches to direct sun. This often burns and cracks the bark, which exposes the tree to infection and other problems. Then there is the issue of fruiting. Hard pruning removes all the fruiting wood, so even if the tree recovers, you are unlikely to see fruit in the next season. What’s the point of that?
The best way to manage the shape and size of an established tree in the long term, without stressing it and robbing yourself of a crop, is to prune annually. A good time to prune is late winter to early spring, while the plant is flowering and setting its fruit. This helps the pruner to judge what they are prepared to lose, and what they want to keep. If you get frost at this time, wait until the risk of frost has passed.
what to prune
The key point to remember is not to give the canopy an all-over haircut, like you would when shaping a hedge or topiary. This removes all of the fruiting sites, which means you’ll get little or no fruit next season. Instead, focus on cutting back a selection of the longest and most offending branches. These include tall upright branches and side shoots that grow beyond the desired size and shape of the canopy. Cut them back to about 30cm inside the line of the canopy you want to maintain. These cuts will shoot, then start flowering and fruiting again in the following season. Aim to cut out about 20 per cent of the canopy each year using this approach. After five years or so, you will have potentially given the entire canopy a chop, without denying yourself a crop or stressing the tree.
To finish up, trim any branches that are touching or nearly touching the soil, lifting the lower canopy to about 1m above the ground. This helps to maintain airflow through the canopy and reduces the potential for fungal diseases. Look over the outer foliage of the canopy for unusual swellings in the stems caused by citrus gall wasp. This is a wasp that lays its eggs in the soft young stems, causing them to swell. Severe infections can weaken the tree, so prune them off and burn them, or seal in a plastic bag and put them in the bin. Tiny pinholes on the galls indicates that the baby wasps have already emerged, so there’s no need to remove these.
Finally, examine the inner branches and prune out any dead, damaged and diseased wood along with any branches that are crossing and rubbing. The bark at rubbing points eventually wears and exposes the inner wood to infection.
LEFT AND ABOVE
Look through the canopy and remove any dead and diseased wood; galls should go, but those with pinholes can stay as the wasps have left the building; reduce the size of old, overgrown citrus gradually over a few years to reduce stress on the tree – the end of the fruiting season is a good time to prune.
PRUNE AN OVERGROWN TREE
A similar gradual approach is best when reducing the size of an overgrown citrus tree. Just chop back a third of the branches hard this year, leaving behind a large portion of the canopy to continue fruiting and supporting the tree as it recovers. In 12 months or so, take out another third, and so on.
1 REMOVE large heavy branches safely by using this three-step approach. Start by choosing a spot out along the branch from where you intend to make your final cut. Make an undercut, sawing about one third of the way in. This stops the bark from ripping and causing an unwanted wound.
2 MAKE an overcut a few centimetres out from where you made the undercut, cutting right through the branch this time.
3 PICK a spot along the branch where you want it to reshoot and make the final cut.
FEED IT UP
Citrus love a good feed, and deservedly so. It takes a lot of energy to grow all that delicious fruit, and they always seem to be at it; as soon as one crop finishes, they are busy working on the next one. Regular feeding and watering is the key to keeping them happy. Give them a feed now and follow up with another one every three months or so. That’s four feeds a year.
There are plenty of different fertilisers available but, for me, organic fertilisers such as blood and bone and pelletised chicken manure are best because they help to support the beneficial organisms in the soil. I like to alternate between different types of organic products to give trees a broader range of nutrients.
When you’re applying fertiliser, pull back the mulch then water the root zone well. Spread the fertiliser evenly under the tree, from the trunk out to the canopy edge. You can apply organic fertilisers at the rate of one handful per square metre. For synthetic types, check the application rate on the packet. Water in the fertiliser, then return mulch to the surface. Follow up with a deep drink every fortnight or so when conditions are dry.
fertilising potted citrus
Citrus in pots need more regular feeding than those in the ground. That’s because basic potting mix has very few nutrients compared to your average soil. Also, because pots are watered more regularly than garden beds, any nutrients that are added are easily leached out.
Fertilise potted citrus once a month with an organic fertiliser applied as a light covering over the surface of the mix (at the rate of 100g for a 100L pot). If you prefer, you can use a controlled-release product formulated for citrus at the recommended rate on the container.
MANAGE SCALE INSECTS
Of all the pests that affect citrus, scale insects are arguably the most enduring. They can be found on almost any part of the tree, including the leaves, stems, fruit, branches and trunk. These sap-suckers weaken the tree with their feeding action, and in large numbers they can cause a lot of damage from leaf, twig and branch dieback, even to the point of death for some trees.
There are many different types, and they are generally grouped as ‘hard’ or ‘soft’. Hard scale insects include California red scale, with its hard, waxy, orange-coloured protective shell under which the insect feeds. Soft scale insects, such as white wax scale and brown soft scale, produce a lot of honeydew (sugary exudate), which causes the black sooty mould you may have seen on citrus foliage and stems (aphids on new growth also produce a lot of honeydew). Ants love feeding on this honeydew and their presence in your tree is a good indicator that there is a thriving population of soft scale in the canopy.
Have a good look over your trees now, inspecting every surface, from the trunk to the underside of the leaves.
If any type of scale is present, spray the affected surfaces thoroughly with a diluted horticultural oil. These oil sprays work by suffocating the scale. If you find you have a heavy infestation, make one or two follow-up applications at monthly intervals. Once the scale insects are under control, any sooty mould that was present will naturally disappear, too.
STOP STINK BUGS
You’ve probably seen these nasty-looking critters crawling over citrus trees in spring, and if you haven’t, then you’re likely to have smelt their presence as you brushed past. Also known as bronze orange bugs, these slippery little sap-suckers not only stink, they also do significant damage to citrus. Like many sap-suckers, they have a liking for tender new growth, destroying the shoots with their feeding action. They also like to suck the sap from flower and fruit stalks, causing the blooms and fruit to fall prematurely. Large infestations of the pest will significantly reduce your crop, so you need to be on a constant lookout to keep their numbers down.
Get to know them at the different stages of their life cycle. As nymphs, they appear as tiny (about 5mm long) light green bugs and gradually change to an orange bug 15mm long. Once they reach adulthood, they get really ugly, so you don’t want to be seeing too many of them, and it’s not just that their large, brown angular features make them look menacing. The adults also lay lots of eggs, which means you’ll be in for more trouble.
I’ve tried all sorts of methods to reduce their numbers, from knocking them off with a stick and stomping on them to vacuuming them off (when your neighbours see you vacuuming your trees, they’ll either ask questions… or choose to avoid you).
The method I find most manageable is to simply pick them off with kitchen tongs and drop them into a bucket of soapy water (see step-by-step, right). Whatever method you choose, persist throughout the late-winter and spring period so that you remove as many as possible and break their life cycle. That way you’ll have less of a problem next year. Also, always wear protective gear when handling them. That stinky stuff they squirt is caustic and can burn your eyes and skin.
STEP-BY-STEP REMOVE STINK BUGS
1 PART-FILL a bucket with water and add a little dishwashing liquid.
2 PUT ON some protective gear – gloves, a long-sleeved shirt, safety glasses or a face shield and hat – then grab the bucket and tongs ready for action. Seek out as many of the bugs as you can, and pick them off with the tongs. They can take some chasing, because they’ll see you coming and skip around to the other side of the twig. Stick at it!
3 DROP them straight into the bucket where they’ll drown. I normally leave the bucket and tongs near the trees for a few days so that I can do a daily follow-up to grab any that I’ve missed. By day three or four, the water starts to get a bit soupy, which means it’s time to tip the contents out somewhere among the shrubs.
PLANT A NEW TREE
Now is the perfect time for preparing the ground and planting new citrus trees. If you’re in a cold, frosty area, hold off the planting until spring when the risk of frost has passed. Consider the brightest, sunniest spots you have in your garden – citrus like lots of sun – and choose one that is protected from strong winds, as wind can really knock these trees about. The soil must also be well drained, so avoid damp and boggy spots.
Take your time preparing the soil. Mark out an area about 1.5m wide, remove all of the grass and weeds, then enrich the soil by incorporating generous amounts of compost or well-rotted manure. If your soil is heavy clay, mix in some gypsum, too, and then shape the improved soil into a raised mound to improve drainage. In the centre, dig a planting hole that’s about twice the size of the root ball.
When you remove the plant from its container, gently tease the roots before putting it in the hole. Position the root ball so the top is level with the surrounding soil, then backfill and firm it in. Shape a circular ridge of soil around the base of the plant to hold water, then water well. Cover the soil with mulch, and keep the soil moist for the first few months as the plant settles in. Don’t fertilise at planting – wait a month or so before adding a handful of organic fertiliser around the base of the tree. There’s no need to stake either – most citrus trees you buy are strong enough to stand up on their own.
PLANTING IN POTS
Any citrus that performs well in your area can be grown in a container, which is great news if you’re short on space or you garden on a balcony. You need a large container, at least 100L (that’s about 60cm wide and 50cm deep – anything else is too small to grow a decent tree), and it must have at least one good drainage hole. In a few years, you could pot it up into a larger container. A 250L container will keep an established tree happy for many years without the need to re-pot. Use only a premium potting mix that has the red Australian Standard logo with five ticks.
Choose a spot that gets plenty of sun, with some protection from the western sun for the first year or two. Place the container on pot feet or bricks, so that the water drains away freely. Keep in mind, potted citrus need more regular watering than those in the ground. Check the mix regularly to see if it has dried out and needs re-wetting. Severely dry mixes that have shrunk and come away from the sides are very hard to re-wet. Don’t delay in rectifying the situation by applying a wetting agent to help rehydrate the mix.
TRY ESPALIER
If you don’t have the space in your garden for a full, round citrus canopy, try espalier. This is the practice of training a tree flat against a wall, fence or freestanding frame. It’s fun and easy to do, and it makes a wonderful feature. I have trained four citrus varieties as espaliers in a row alongside my patch in a bed that is only 50cm deep. To guide the branches, I installed horizontal wires spaced 45cm apart, but you could also use lattice or some other type of frame. As the branches grow, tie them loosely to the wires or frame. If anything protrudes too far outwards, chop it off. It’s really as simple as that. There are many shapes and styles for training espalier, from a horizontal cordon to a candelabra, but the style that works best for citrus is the natural fan shape, which mimics the trees’ normal growth habit.
You can train citrus in lots of other interesting ways, too. One of the most memorable examples I’ve seen was in the gardens of Villa Carlotta on Lake Como in Italy. Here, the trees are trained over a long timber arbor, creating a leafy tunnel with branches laden with fruit dripping down overhead. Now that’s a project I’d like to try… one day.