Why are my plants going red?

[William]

Several of the plants in my garden have gone red and don't look very well.  The lower parts of the mint have gone dark red and it's pretty much stopped growing.  The eucalyptus tree has a lot of red leaves that then drop off - the whole tree seems to be falling over now too.  A few herb seedlings went red for a bit but seem to have got better.  My chilli plants have gone yellow as have a few other plants.  Other plants seem fine.  I don't think it's dryness.  Is this a plant virus (or over/under feeding) and what can I do?

[Robinia]

You say William that you don't think it's dryness, but if you're in the UK I'd hazard a guess & say that it probably is.  I don't think that many places, if any, have had much rain this year, & along with the cold winds/nights a lot of plants are suffering.  I can't help you with your leaning eucalyptus I'm afraid, I'm assuming it's a tall one? 

[woofgang]

That redness can be a symptom of young plants getting chilled before they are hardened off. if you have a cold night after a few warm days and the shoots are still fragile, they will redden and the growth will slow. Sorry, can't help about the eucalyptus though

[auldyin]

It could be red spider mite attacking your plants. Check the underside of the leaves for mites and traces of fine web. You can get sprays from the garden centres for this.

[William]

Thanks all.  No sign of spider mites.  Woofgang, you could be right on the hardening for the mint - it was green (and growing fast) inside, then went red (and stopped growing) when moved out (although it was May when moved so thought would be ok).  Signs of new, green growth now. Eucalyptus getting a good soaking now so hope that will help it.  Yes, it's tall and (was!) well-established.

[greenfingers]

We have had exceptionally cold nights this month, I suspect this is probably whats happened. It is mirroring what occurs in Autumn and gives us all those reds and golds.