hi all, watered my kumquat - and the next day it dropped half it leaves, the new growth on the plant turned a rusty colour, any ideas?

too cold an less air at root level , you have suffocated him , try to put it on some heated mat to evaporate much of the water to reestablish the balance air-water-temperature inside the pot and evverything is ok , but you should do it a.s.a.p
Daniel

This happened to my kumquat too last year during summer after I put some fertiliser in its water for the first time, it was doing well up to that point. I looked at the bottom of its pot and through the drainage holes I could see some nasty looking white fungus type thing. I'm guessing the fertiliser boosted the fungus which traumatised the roots causing leaf drop? I read that cinnamon, rosemary, oregano, basil, and chamomile are all anti-fungal so I made a herbal tea with all of those combined and watered my kumquat with the tea for a while, and also sprinkled a light layer of cinnamon directly onto the soil once or twice. Fungus at the bottom seems to have died. I now give it fertiliser but it still doesn't look healthy like it did when it first arrived. I'm hoping it will liven up when spring comes around.

One thing is for certain. The problem your tree is experiencing is in the root zone. Actually with containerized citrus trees that are grown in northern areas outside of the citrus belt, almost all problems the tree experiences is inside the container. To know what the problem is, you need to slip the tree out of the container and examine the roots. This wll tell you what the problem is. - Millet (730-)

thanks for the replies it has lost no more leaves, it is on a heatmat anyway and has a thermostat.....will check the roots, i did water it with cold water out the tap has that got anything to do with it? all my other trees are good.

boost-boy74,
I'm completely with Millet on this one. I had a similar issue:
link
Since then the tree is kept in non-heated area over winter and looks better every year. Seems to me that I could expect recovery to be finished this season.

thanks guys - i have a 4 seasons lemon that just dropped all its leaves after being repotted into chc, maybe its root rot on both plants? what do i need to look out for when i have taken the pot off?

cheers si

boost-boy74,
While you wait experts for answer here is something for read:

Millet wrote:

Sure, just carefully slip the three trees from their containers and check the roots. You can turn the container upside down, holding the soil with you hand, and slap the bottom of the container to release the root ball. - Millet (746=)

at link

"help for leafless lemon tree" at
link

or link

Also you can play with search engine and search the forum for WLD (Winter leaf drop), etc.

Or Google,
Just found this generaly interesting link: "List of citrus diseases"
http://en.wikipedia.org/wiki/List_of_citrus_diseases

started to get leaf drop on my other trees - they are all in citrus peat/chc and on heat mats - its only after i water, is my water too cold? is it too much fertiliser? please help

At this time of year, every year, there is a lot of leaf drop. With the start of the new spring flush and blossoming season, a citrus tree will also begin to drop many of its older leaves. The leaves that the tree discards, are not necessarily only the older yellow leaves, but also some green leaves as well. In greenhouses with a lot of citrus trees, the floor is frequently carpeted with fallen vegetation. - Millet (678-)

boost-boy74,

This happens with me also in the past and this is caused by the cold water which suddenly drop down the temperature in the root zone. Warm up a bit the water before and no leaf drop will occur.