For about 5 or 6 years I have been using a mixture based on coconut husk chips for my potted citrus. The mix usually includes 25% peat and 25% perlite.
I avoid frequent repotting, as I haven't got enough room for many larger plants in my greenhouse.

Apart from a brief burst of summer in March (when I moved all my many pots out of the greenhouse), temperatures here have been mostly well below 70F 20C during the day, and usually around 50F 10C at night. It has rained frequently and heavily and many of my plants are suffering.

I have therefore started a programme of emergency re-potting - this time based more on the gritty mix principle, using Diatomaceous Earth (sold here as cat litter) as a water absorbent and oxygenating ingredient.
See http://www.bonsai4me.com/Basics/Basicscatlitter.htm

During this re-potting, in pots last changed over 2 years ago, I have found that the CHC mix has virtually completely broken down into a smooth consistency. With the frequent cold rain this is wet and soggy, and many roots have rotted away. I am completely removing the old compost, washing the remaining healthy roots, and replacing with the new totally inorganic mixture.

I'd be interested to hear how often other people re-pot their citrus plants (especially anyone in cool wet climates), and any comments on the long-term use of CHC mixes versus inorganic, gritty mixes.

Mike/Citrange

Mike, the gritty mix can be a good mix, it can work well, and it does lasts a long time. The real draw back I had experienced with the gritty mix was its weight. Most gritty mixes include granite as one of their main ingredients. Therefore, its use is limited only to small containers, growing smaller sized trees. I have a Pommelo tree in a 32" high X 60" wide ARP container. A gritty mix in this container would weight many 100s of lbs. For a small container sized tree I think you might like it. When I tried the gritty mix, it worked OK during the winter, but during the hot summer days, the container had to be watered some times every single day, or at least every other day. With the UK's weather you might not have that severe of a problem. Here the temperature has been over 100F (38C) every day for the last week. I wonder what the buffering capacity is of the gritty blend, probably not much. Good experiment you are beginning, let us know how you value the mix after you have had time to evaluate it further. - Millet

I agree with Millet about the gritty mix. I used it almost exclusively until recently when I changed to a bark based mix. There are many theoretical benefits to the gritty mix such as long life and excellent drainage. One major downside is the weight. It is nearly impossible to move around large containers. The other major downside is that the mix needs to be watered daily in really hot weather, especially when the humidity is low. As Millet mentionned this may not be as significant an issue where you live compared to my own experience in California. Lastly, be very careful about re-potting plants into the gritty mix, particularly when they are in a traditional potting soil. It is best to bare root plants when changing over to the gritty mix, otherwise many of the advantages of this "soil" are lost. I have had many plants die after being re-potted into the gritty mix, even when I very carefully bare-root them. The gritty mix has a greater tendency to clump and centralize the roots. You must be very careful about spreading out the roots so that they are more homogenously distributed within the mix, as opposed to being clumped.

-Brett