By Dennis Ting
In the Part 1 of Growing Dwarf Potted Citrus I outlined how to select a tree, a pot, potting mix and plant up your young tree. I have spent the last 12 months observing my own trees and they have had to cope with extreme conditions of heat during the last summer. I am happy to report that I have refined my techniques and suffered no tree or even crop losses by following a few important rules. I include some photos to illustrate the range of citrus I am now harvesting Lemons, Limes, Mandarins, Oranges, Tangelos, Tahitian Limes etc.
Consistent deep watering is most important during the warmer months and I cannot stress this enough as citrus cannot get too much water at this time.
The potting mix must not dry out ever as you will get significant flower and fruit drop.
Citrus have glossy smooth green shiny leaves and when they become pale and feel like leathery leaves the plant is water stressed already. Dig into the potting mix with your fingers and you will feel it is probably quite dry underneath. Use a jet nozzle on hose to punch four holes into top of the pot when watering to ensure potting mix is re-wet through not just surfaced watered. Continue to do this all summer if necessary as citrus love their water.
Mulch well with light coloured pea straw all during summer to reflect the sun from the darker potting mix and add nutrition.
Humidity at night can be increased by spraying the foliage which improves flower retention and fruit set.
Liquid fertilizer every two weeks on the foliage and soil at night or early morning alternating between a Seasol / Powerfeed combination with either Thrive Flower and Fruit or Phostrogen from September to March.
I find an infrequent two monthly water with worm tea compost diluted at a ratio of 1:10 can also be beneficial but it can be alkaline so should be used sparingly.
From April cut back fertilising but some is still needed to size up and colour up the fruit.
Healthy citrus trees do not get troubled by much as long as you feed well and keep them growing as I have never had problems with scale, aphids or citrus leaf miner. Citrus Gall Wasp is a problem I have but if you hang the yellow gall wasp traps in the trees from July to catch the emerging flies in spring you should minimise the infestations. Another method I have heard of is to slice vertically over the galls as this exposes some of the larvae to air and kills them while the sap can still flow up and down the branch. Lemons and limes are the most badly affected while oranges and mandarins just suffer from the odd gall that does not seem to cause too many problems.
As I said above just keep the tree growing as cutting back is not really an option on dwarf trees as you weaken the tree and it becomes smaller and smaller.
I would now like to introduce my ‘Zen Defensive Method of Pot Placement’ which again was of some benefit during the extremely hot weather last summer. I place my plants in a ‘North – South’ line with pots ranging in size from a few at 400 mm to the majority at 300 mm and a few smaller ones at 200 mm for young trees. Remember from Part 1 the pots are a light terracotta colour and not black so do not absorb the heat from the sun. The pots are almost touching and would get hot summer afternoon sun but the branches are allowed to grow into each other to provide mutual shading and shelter.
Next to the ‘North – South’ line is a deciduous Walnut tree which also provided some light shading but not too much. They appear to grow well like this than if I pretended they were in an orchard situation and spaced them apart individually. I do have a few larger plants in pots which are spaced well apart and they suffer a bit during the warmer weather but can be successful too.
I have not found much pruning necessary at all except for shaping and cutting back to encourage branching for the stronger growing lemons. Thinning of branches before the flowers emerge in spring appears to conserve energy and result in a better crop of well sized fruit.
So now you have enough information to grow your dwarf potted citrus to produce useful crops of full sized fruit to perfection in your own garden.