Plant Doctor Archive

Fruit split on citrus tree

I have a citrus tree named Tangor Dweet which I planted about four years ago. The tree has grown normally and looks reasonably healthy. The fruit however never gets to mature before they split. Initially I didn't put anything on the tree. I have tried lime and fertiliser at different times. Watered at different rates, etc. Yet always the fruit splits.

Fruit splitting is believed to stem from stress as a result of extreme fluctuations in temperature, humidity, moisture availability and possibly fertiliser levels. For example in hot, dry weather the tree will become drought stressed and will draw water from the developing fruit, causing the skin of the fruit to soften. If the tree is then given a heavy watering, the dehydrated fruit will swell, causing the skin to split.

Young citrus trees that are not fully established, dwarf varieties with shallow roots, and trees that are grown in sandy or porous soils do not retain water very well, and the same can happen to these. Regular watering is therefore essential until the tree has become fully established.

High humidity after a dry period can also be a trigger for fruit split, and rinds that have been sunburned or otherwise damaged can lose their elasticity and therefore be susceptible to splitting.

Remove any damaged fruit and monitor your tree's irrigation levels to avoid major fluctuations in soil moisture. Water deeply once a week in the growing season and mulch to keep the roots cool and moist in the drier months.

Citrus trees enjoy a slightly acid soil, so adding lime will only make your soil more alkaline. Zinc and iron are locked up by the soil in alkaline conditions, so your tree may start to develop symptoms of a trace deficiency — yellowing of leaves.

Citrus trees also need regular feeding, including large amounts of nitrogen and potassium for good fruit development. A mature tree should be given 450-500 g of citrus food every year (you can buy specially blended citrus food such as Yates Gro-Plus Citrus Food). Two-thirds of this amount should be given in July or August and the remainder in January or February. The ground beneath your tree should be watered well before and after applying the fertiliser. The fertiliser should be scattered around the drip line of your tree. This is the area underneath the outer foliage where, literally, the drips fall down when it's raining.

The key here is watering and feeding. Once you have this to a regular pattern, you should see an improvement in your fruit.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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