Friday, February 20, 2015

Feeding citrus in pots

After my last posting on feeding citrus, several readers have emailed, and 'Anne at Home' left a comment here, asking about feeding citrus in pots, so here's my combo-reply posting to all you potted citrus persons.

How often do you feed them? Aim for monthly if you can (and that is so much easier said than done. Remembering is the hard part. I try to remember to do it around the first weekend of every month, but even keen-as-mustard-me forgets sometimes.)

Happy Thai limes.
Happy Thai lime in a pot.
How much do you feed them? Not a lot. Light feeds are best. 
• For my "flinging in the rain" I used one handful of chicken poo, which is about 75 grams.
• If I use a liquid organic plant food, about one whole 9-litre can (made up according to the instructions on the pack) per month is plenty for my mature trees in big pots.
• If I use a slow-release food, I apply 3-4 tablespoons of pellets to a 45cm diameter pot, and that lasts 6 months (a good option over Sydney's mild winter, or if you're away travelling).  

What do you feed them? Well, I like to mix it up a bit, but that's not essential. Over the last two years I have fed my potted citrus with:

Dynamic Lifter (organic chicken poo)
Dynamic Lifter Plus (for citrus, organic chicken poo with fruiting and flowering additives)
Osmocote for Fruit and Citrus (slow-release granules, lasting six months per application)
Powerfeed organic-based liquid food for fruit and flowers
Nitrosol organic-based liquid food

The reason for the mixing up of foods is mostly that was what was in my shed at the time, and all of them work fine, so for convenience's sake I just used whatever was there.

Our former cumquat tree, now happily
domiciled at Louise and Antonio's place.
Essential ingredient for cumquat marmalade!
A little bit of potted citrus whys and hows...
It's not just potted citrus that need to be fed more often, but lightly. It's everything in pots. Each time you water a pot, some of the potting mix's nutrients are washed away, out through the drain hole. Eventually all potting mixes completely run out of nutrients, and plants then might start to get unhappy (although some plants are more fussy than others, and citrus are world-class fuss-pots).

So, the big tip is that you need to constantly replenish a potted plant's food supply with little doses of food. Once a month is dandy.

That's why slow-release foods like Osmocote are so excellent for pots. They were originally designed (in California) for potted plants, with the special coating around each little pellet formulated so it releases its doses of nutrients more readily during warm and moist weather (when plants grow best) and releasing its nutrients more slowly when it is cool and dry (when plants grow slowest).

Furthermore, slow-release potted plant foods have the added advantage that you don't have to apply them so often. Depending on the product, they can last either three, six or 12 months. The Osmocote for citrus lasts 6 months.

The only drawback to slow-release foods is that they are not organic. They are just very sophisticated and extremely useful modern chemical plant foods. 

However, if you want your garden to be an organic one, especially your food garden, then I suggest the easiest organic food to apply is the liquid type, where you mix up a capful of concentrate in a can of water, and apply that to the pot. For a mature potted citrus tree, one whole can of 9-litres is plenty for a potted citrus in a big (45cm or more diameter) pot. If you have a smaller baby citrus tree in a pot, use your common sense and halve that amount, maybe even cut it down to one-third. (Mix up a whole can at a time, though, as the leftover liquid foods are great for any flowering food plant, from cucumbers to capsicums, tomatoes to zucchinis, etc etc). 

Hope this helps. Just remember, with the old saying about organic plant foods: "If it doesn't smell bad, then it's not organic!"


Amy Crumbs said...

Thanks for the reminder to fertilise. I've definitely neglected my citrus. Also thank you for explaining the washing away of nutrients - something that probably should've been obvious to me if I'd thought about it properly. Will certainly stick now!

Anne At Home said...

Thank you Jamie, a whole post for my answer, I'm chuffed! Based on your advice I think I'll do the monthly chook poo over the warmer months, then slow release citrus food over the cooler months. My lemon tree is a feature pot on my balcony off the kitchen, so it's eyeballing me everyday ensuring (theoretically) that I won't forget. I've also given it a (roughly) monthly watering can full of seasol or Charlie carp, depending on what I have. Thanks again, I'm a loner in the edible garden stakes around here, so value your advice! Have a lovely weekend, nice to get a sprinkling of rain in this heat! Regards, Anne

Jamie said...

Remembering is half the task with fertilising!

I'm glad the posting has helped. Charlie Carp is good stuff (my accountant Michael, a keen gardener who reads my blog sometimes, says "Plug Charlie Carp more often, it's good stuff").

The Seasol is also good for plants, but remember that it isn't a fertiliser. It is more like a "general health tonic" that promotes root growth and beneficial soil organisms, but it contains no actual plant food. I use Seasol too (or its powdered equivalent, Eco Seaweed). It works best on baby plants, or on sick plants that are under stress.

Jem @ Lost in Utensils said...

Thanks for the tips Jamie. I have quite a few citrus trees growing in the ground and I have a bit of a love hate relationship going on. They also love chook poo and charlie carp every now and then. Occasionally I use epsom salts as my soil can lack magnesium and it works a treat. Stink bugs can sometimes be an issue, do you have problems with them? I usually just remove them (I'm an organic gardener) but would love any advice. One tree which always produces an amazing amount of produce is the cumquat. It's unbelievable!

Jamie said...

Hi Jem

Yep, stink bugs are an annual problem here, too. I use Pyrethrum spray, which is a naturally derived product (from a type of daisy) and is good that it only works on contact with the thing it zaps. I don't use it in the mornings or evenings, when the bees are busiest.

It's not a nasty "systemic" spray which hangs around the plant for days or weeks and murders every little insecty guy who visits the plant.

However, it does have a one-day withholding period, which means you shouldn't harvest from the tree for one day after using it. So you couldn't call it a truly organic spray, but is the lowest toxicity, most effective one I have tried. Several years ago I tried to remove the stink bugs by hand, but it was smelly, messy, a bit dangerous when doing it on step-ladders, and generally unsuccessful. So I have used pyrethrum since then, very cautiously.

And I, too, have a packet of Epsom salts in the shed, but I don't use it much. I think it might be that manufacturers include a little bit of magnesium in the additives that they incorporate into their boosted "organic-based" plant foods. So if you fertilise with the boosted products, you're probably already adding some magnesium to the soil.

Shivangni said...

Thanks for this post, I do remember your last post on citrus and have been showing off my knowledge based on that (washing away of nutrients etc), will be able to add to my boast basket.

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