Hibiscus

Please does anyone know what and when I should fertilise an hibiscus.

If you are referring to the hardy deciduous Hibiscus syriacus varieties, like 'Blue Bird' or 'Hamabo' then you can feed them any time now with a balanced fertilizer.  You can also hard prune them which is often recommended as it should produce long shoots with flowers all along the stem. 

I fed mine about a month ago as it was convenient and I'm now going to prune them a bit. 

Many thanks Salino.

I hope you don't mind me hijacking this thread but I wanted to ask about my Hibiscus Lilac Chiffon. I have had it for about three or four years now, originally I had it in a pot and it didn't do much so I put it in the ground and it has yet to produce so much as a bud! please can anyone advise as to how I can get some sort of display from it? Thanking you in advance

I think you mean 'Lavender Chiffon....?'  they do prefer moist soil yet also in full sun [a difficult combination to get right], a generous feed at this time of year too.  Don't know what can be wrong otherwise, it should flower even if you don't prune it.