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I saw an article in the February issue about a potted cumquat that was only re-potted three times in 25 years. It was done by regularly removing potting mix with a bulb planter and replacing it with fresh mix. How much mix do you replace, and when? My cumquats ower but don’t fruit properly (the small fruit fall o the tree), and some have died. ey are in plastic pots and 45L bonsai bags. Should they be in terracotta pots instead? Of what size? How do you water them in summer and winter? Alvin Obsioma, Derrimut, Vic DERYN THORPE SAYS Citrus grown in pots need extra attention to thrive, including regular fertiliser, trace elements and water. However, the tips below will work for other potted trees, such as camellias, Japanese maples and gardenias. My cumquats and citrus have been grafted onto dwarf rootstock in pots 45cm wide. They get at least six hours of sun each day. Pots can be plastic, terracotta, cement or fibreglass but must have adequate drainage.
In wet-winter climates, elevate pots on ‘feet’ to allow excess water to get away. Use a premium potting mix with five red ticks on the bag. Each year I use a bulb planter to take out about four lots of the spent mix. I throw it onto a garden bed and replace the holes in the pot with fresh mix. I add six-month controlled-release fertiliser twice yearly and water them fortnightly with a fertiliser that’s a mix of fish emulsion, liquid seaweed and liquid compost, as frequent watering flushes nutrients from the pots.
I mulch with 3cm of compost twice a year, and cover this with lupin mulch or pea straw. These conserve moisture, protect the plant’s surface roots and provide nutrients as they decompose.
Once a year I spray the foliage with complete trace elements, and I repeat this if there are signs of nutrient deficiency, such as discoloured, yellow or curled leaves. I water them three or more times a week in summer, when the pots dry out quickly, but only once a week in winter, as my area receives winter rain. Before watering, I check soil moisture by inserting my finger about 3cm into the mix. The soil should dry out between waterings, as citrus hate wet feet.