In message k2gDc.66$%m5.56@newsfe4-gui, Poppy
writes
I grew some Datura from seed earlier this year and they've reached about
10cm and seem to have stopped growing. The bottom leaves keep yellowing and
dropping off - I've tried watering more and I've tried watering less and it
seems to make no odds. When they are watered they get a weak solution of
seaweed feed in with it. Any clues as to what I'm doing wrong?

Sounds like there isn't enough fertiliser to satisfy it so the lower
leaves are being used as plant food. Try Epsom salts as a foliar feed to
halt it.

They like warmth and plenty of very rich soil for lush growth with high
potash fertiliser to encourage flowering. Tomato feed is a pretty good
cheap choice. You will be amazed how big one can get in a year.

It is quite difficult to over pot them.

Regards,
--
Martin Brown