John, The spots you describe still looks like sunburn to me. Its caused by the UV light the first time plants get into the sun. The weather in Holland has been very sunny for the time of the year and so plenty of UV in the air. But normally doesn't happen when there is glass in-between which blocks 90% of UV, but perhaps your greenhouse has Plexiglas (unbreakable) windows which is a good transmitter for UV wave length. Just my two cents Rob NL ----- Original Message ----- From: "John Clark" <john@callcentrevoice.com> > the plants have white, paper-thin patches on some leaves. There appears = > to be no pattern to this, and none of the plants seem worse for it. = > I've picked off the worst affected leaves, but on some it's a speckled = > effect and on others it's at the tips of the leaves and in some cases in = > the middle. Strange. I firstly thought about the sun, but it's March, = > it's Scotland and we don't get too much sun. Can anyone suggest what = > this might be and what I can do about it? > > All the best, > > John