[Trillium]

It's always possible that the rhubarb leaves were stressed somehow this year and whatever gave a good flavor before no longer does now.

[pfg]

From the same seeds, some of my courgettes are dark green, some more mottled with yellow.  I think it is just the dark green ones that are bitter - I steamed some with some other veg and swallowed only one mouthful of the spinach and tasted the peas and courgettes.  All were inedible, tainted and bitter and I blamed the spinach for being really ill later.  However two days ago I had two of the courgettes (no bigger than 4 inches each and mottled in colour) and they were fine.  Yesterday I cooked another (dark green) and that was also inedible it was so bitter.  Unfortunately I dug out all the spinach!
The courgettes haven't been fed with any liquid feed, all had poultry manure and home made compost dug in before planting - nothing else on them, but it only seems to be the dark ones (I think) but I daren't try any more.
Is it something to do with the colour?

[pfg]

I've just found the following on the RHS website:

The bitter taste of some fruit is caused by an over-production of plant defence chemicals called ‘cucurbitacins’. This is mainly a problem in courgettes and summer squash and is caused primarily by a mutation within the plant. The problem is more likely when plants are grown from saved seeds, where inadvertent cross-pollination may have occurred.

Affected fruit should not be eaten as it causes stomach upsets and affected plants should be removed.