Question Citrus trees losing leaves due to heat?


Staff member
May 27, 2012
Bellmere, QLD
I live in Arizona and have beautiful citrus trees that I love. In the late summer, it gets really hot here, my grapefruit tree lost 90% of its leaves. Then new growth leaves were small and kind of light green in color. I don't know what to do! Any suggestions would be greatly Appreciated!

The question above was sent to me via email so I thought I would post my answer here in case it may help others and also to invite anyone else to comment or answer.

I live in a hot (subtropical) climate where the daytime temperatures in summer can sometimes rise above 40 C (104 F) with very high humidity so yes that's very hot but perhaps not as hot (on average) as Arizona. Nevertheless, the only time I've seen bad leaf drop on my citrus trees is during prolonged dry spells or under heavy pest attack (such as aphids).

I'd like to know if you noticed all your citrus trees dropping leaves during this period or was it only the grapefruit tree?

Because if it was only one tree showing these signs of stress, it could mean an isolated pest attack or some type of disease affecting that particular tree and not be climate or heat related at all...

My best guess is the tree was under water stress and regular watering during the hotter months and HEAVY mulching around the base of the tree would help dramatically. However, if you were positive the tree was receiving plenty of water (which citrus do like BTW) and the tree's feeder roots are mulched well, then it could be a root problem either a disease, pest, or root bounding that is preventing the tree from taking enough water.

If you establish no root problem, and the tree gets enough water plus is mulched well but the leaves are still falling then try a cover over the tree of a light grade of shade cloth (about 30%) and see if this helps it get through summer.

Lastly, don't forget trace elements! Citrus are hardy plants but they do need trace elements with micro minerals and nutrients otherwise they will become susceptible to stressors. I know in my case our soil is poor (being clay based) so I feed our citrus trace elements every year and if I see any signs of leaf discolouring or problems I give the tree a hit of general trace elements and minerals - it usually quickly fixes the tree up within weeks.
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Valued Member
Premium Member
Sep 27, 2015
Pomona, Qld
Yes I agree Mark, re water stress.

Can I also add that I have recently noticed a decline in the values of content in bags of fertilizer.
There seems to be more fillers & less quality ingredients so the usual handful no longer contains enough nutrition for the plant.

So if a citrus has usually been given 4handfuls of fertilizer for example, nowadays that would not be enough. You would have to give 5 handfuls now to provide the same amount of nutrient that was previously contained in 4handfuls.

When that shortfall is added up over time, the result is a tree that slowly begins to show unhealthy signs. Nothing specific but just general lack of vigour & perhaps more pests than usual.

When that is accompanied by water stress, the results could be severe.
The smaller pale yellow new leaves makes me think that the lack of water is amplifying a nitrogen shortage. When moisture is in short supply, many elements cant travel through the plant so the plant exhibits apparent shortages.