In message , soup
writes
Spot (and identify if poss) the cuckoo in the nest. Son had planted a
tray of sweetpea seeds; most of them have come up, but one plant looks
totally different to the others. Probably its seed looks pretty much
like a sweetpea's seed (son has lots of difficulties so he would not
notice if it was subtly different , but I am fairly sure he would
notice if the seed had been glaringly different).

http://www.sidtech.co.uk/iu/soup936104423291.JPG

I wouldn't be certain of the assumption that the odd one out came from a
sown seed and not from contamination of the compost.

I agree with Dave Hill that it might be a vetch, and that doesn't have a
seed that could be mistaken for a sweet pea's - it's several times
smaller.
--
Stewart Robert Hinsley