My Guide to Growing Citrus

For 20 years I’ve been on Garden Talk Back Radio on the ABC Southeast of SA and I get asked a lot of questions about citrus, and what I’ve observed from nearly 30 years in horticulture, is that they can be slightly temperamental when newly planted.

They have this 2-year window where they sit there deciding whether they want to live or not, and in that 2-year window, do very little. They might drop their leaves as if giving up, then replace them as if saying “nah, I’ll give it a go”.

They continue this live/die pendulum before making up their mind. It can be very frustrating. So, if you’ve planted a citrus and it’s just sitting there doing nothing, you’ve just got to wait it out until it makes up its mind.

Why does my Citrus die?

If your citrus keeps dying on you, there are usually two main causes. The first is wind. Citrus hate wind when they’re young. Indicators that your citrus is suffering wind damage are curling leaves or leaves browning on one side and then falling off. If your citrus is planted on an exposed site, consider placing a hoop around the plant covered with a thick shade cloth to give it some wind protection. Once it establishes itself, the hoop can be removed, and your citrus should be tough enough to survive on its own.

The second cause is usually to do with the soil. Citrus don’t like wet feet. Often, people who have clay soil try and fix the problem by digging out a hole, planting the citrus in it and then backfilling with good soil or potting mix. This might sound like a good solution, but you’ve essentially made it a sump for it to drown in.

The water pools in the hole and has nowhere to go, so the roots rot and the plant dies. Citrus plants have quite shallow roots, so I’ve found the best way to overcome this is to mound up the good soil on top of the clay or heavy soil and plant your citrus into the mound. Flatten out the top of the mound slightly to create a bowl-shaped reservoir. The water is then able to pool in the reservoir, soak through the soil and then drain away freely. This works!

What is the black mould on my tree?

If you’ve got an established citrus tree, you might find that it occasionally suffers from sooty mould. I have this problem with some of my own citrus and it can make the tree look quite sick and unsightly.

Sooty mould is a fungus that feeds off honeydew. The honeydew secretion is caused by a pest called scale. Scale looks like a fish scale and is a sap sucking insect and sucks the sap out of your plant. So, essentially if you get rid of the scale, you’ll remove the cause of honeydew, and so won’t get black sooty mould.

I’ve had success plugging some Confidor tablets into the ground at the base of the tree and the tree will absorb the insecticide through its root zone. Confidor is a synthethic pyrethroid and can be purchsed as a concentrate liquid that you mix up and spray or get already mixed. The only problem with this is that it doesn’t last as long as the tablet and also it can kill bees if it lands on them. The confidor tablet lasts for around 1 year so it’s my personal preferance.

I’ve tried many other things like neem oil or white oil, but I also know that these work by suffocating the scale insects and if you miss some, then you still have the problem. Also, if it rains it can wash it off as well.

I have had a thought on this problem based on my own experience, and I’d like to go one step further. Scale insects are moved from tree to tree by ants. Ants move scale around the tree, farming them so that they can consume the honeydew. So, my question is, if you control the ants, do you then control the problem???? I am working on this as a solution. Let me know if you have tried this?

Finally, on one tree that just wouldn’t recover, I hacked it back to 75 cm off the ground, with no leaves of branches. Just a stump! Yep, that sounds crazy and it took 3 months to reshoot. (I was just about to rip it out) Now, it’s healthy and has grown back so well.

Should I feed my Citrus?

When it comes to fertilising, citrus trees are hungry. You can probably get away with not feeding them and they’ll throw you fruit here and there, but to get a great crop, you should feed them every season. I have a young citrus, Buddah’s Hand, that is about 1.5m high that was being lazy and just existing. I, very generously, tipped up half a bag of dynamic lifter that was lying around all clumped together at the base of the tree (basically because I left it out in the elements for so long that it went hard, and I was mowing and couldn’t be bothered moving it far). I didn’t even spread it out, I just left it clumped at the base of the tree. Sorry! Within a couple of months, this tree went nuts! It’s full, lush and now has about a dozen new fruits growing out like alien fingers or creatures from the deep. My tip: feed them and feed them often. I know you need to feed them, but I treated mine like some poor starving child in a third world country. I also have sandy and gutless soil, so I should also mention here that there are some people that have beautiful volcanic, rich soil that might not need feeding. Rare but does happen.

I like to use Sudden Impact for Roses as my go-to fertiliser. It has a higher potassium amount than regular fertilisers, and roses and citrus are both “gross feeders”. Not gross as in “ew gross”, but gross as in hungry. This fertiliser is good for flowering, fruiting and also strengthens cell walls. Plus, I love anything multi-use, and this fertiliser does everything. Also, Roses and Citrus are in the same family and it’s good to know that you can just use the one fertiliser instead of having to buy 10 different ones.

Which variety should I grow?

Lisbon Lemon is a fantastic backyard lemon tree. It has thick skin (perfect for making preserved lemons as you mostly want the rind more than the flesh) and fruits all year round. But this plant wants to be a tree. Don’t try and contain it or prune it like a shrub. It will want to grow like a tree, so best to let it do its thing. It is one of the only plants I know that has full fruits, have ripe fruits, buds and flowers all at the same time, so when I say that if you only have space for one lemon tree, make it this one and feed it a lot more than you do. (that was a note to self!)

The second lemon I’d choose would be a Eureka Lemon. This tree fruits for 4-5 months of the year and has beautiful, thin-skinned lemons with plenty of juice and no seeds. Gorgeous for zesting, and lots of juice for preserving and making lemon squash. It does, however drop them all in one go at the end of the season which can leave you in lemon surplus. But I don’t mind that because I love to make Lemon Squash, which is a preserve. Mix with soda water for the best tasting lemon squash drink. I have a preserving book for sale on my website if you’re keen on this type of thing. It’s up to its 4th reprint, which I’m pretty chuffed about!

If you like limes, I suggest planting both an Australian Lime and a Tahitian Lime tree. Each one fruits for 6 months of the year at the opposite time of the year, so if you plant both of these trees, you’ll be harvesting limes all year round. Perfect for cocktail making. The best part about Citrus and limes in particular, is that they freeze whole, so well. You don’t need to peel or anything, just shove them in the freezer, grab it out when you want to use it and give it 30 second to defrost and away you go in whatever dish or drink that you need it in.

Oranges? I have a really big soft spot for Washington Naval as it fruits from winter to spring, It just hangs on the tree doing it’s own thing from mid June onwards, sometimes until November. (but I’ve usually eaten them by now) There is no way you can purchase the taste of a freshly picked orange. I don’t mind them a bit on the tart side but I can’t stand them when they are supermarket dry. (if you know you know. )

Valencia Orange fruits from summer to autumn. Which is so handy and these are usually sweeter and larger and if left not well watered, can go dry. But that is quite easily fixed by watering. Plant both and you’ll have oranges all year round.

There are heaps more Orange varieties like the Blood Orange and the Cara Cara Orange, Seville Orange (the bitter one for marmalade) If you have space then grow them all!

Mandarins can be a bit of a diva and I haven’t had much success growing them where I live. They each fruit around the same time, with maybe a month or so between them. Emperor, Ellendale and Imperial are the most popular. I’ve just given mine the “talk”and one of them has listened and is now acting according to my horticulture qualifications, but seriously, they take a few years and love protection and rich soil and they’re from sub temperate regions, so, worth trying and see. I’m out of town and I know a lot of people in town, with richer soil that has an amazing Mandarin tree. The one main question I get asked about Mandarins is that they can be dry. The reason for this is not enough water. Most of the people that complain of this have a large tree and they think it’s healthy so it’s all good, you don’t need to do anything, but in reality Mandarins need more and consistent water than just a shrub in garden.

If you like to cook Thai food, I suggest planting a Kaffir Lime tree. The fruit is nice, but it’s the leaves you want. They’re beautiful, with a double leaf on each stem, and you only need a small amount to add amazing flavour to your dishes. The leaves can be expensive to buy, so having some fresh and handy in the garden is a must for anyone who loves to cook. Either add a couple to your Thai Green Curry, or to rice that you’re cooking or I also love it with other Citrus in a hot, lemony tea.

Finally, what I’ve found with citrus is the least hardy citrus trees are usually the tastiest. Typical! Grapefruits, limequat, kumquats etc are incredibly hardy trees, but you usually have to do something with the fruit to make them truly shine. Funny how Nature works!