Sunflowers.
 

I've got this sunflower. It is thriving away in a 5" wide and pretty deep
pot on a south facing windowsill getting full sun all day.

I know I should plant it out, but I'm currently living in a shared house
(supported accommodation) and I need to organise a workshop one afternoon
where we tidy up the little garden, move out a lot of rubbish and make
things garden-able.

My windowsill is crammed with seedlings (well plantlets) of herbs
(oregano, basil, parsley, chives and thyme) and perennials (lupins and
dahlias mostly). About half is potted on into 3" pots.

But... this sunflower. Every evening it droops. All the leaves lose their
rigidity and it appears to wilt. By dawn it is perking up and by full
light is looking strong and healthy again.

It isn't down to watering because it is kept moist and sits in a tray
that I usually prevent from drying out. It isn't pot bound yet (no roots
sticking out of the base). If it was out in the garden, I'd assume that
it needed a bit of a drink and aim a few gallons that way during the
evening watering.

I *think* this may be part of the respiratory cycle of the plant that
I've never noticed before because I've never been daft enough to live
with one in my room.

Has anyone else ever noticed this behaviour from them?

As the thing has reached 2' I'm half tempted to pinch out the tip and
have it flower lots of little heads on my windowsill, but I'm not sure I
have a pot that'll be big enough and still fit on the sill :)

Warwick

I've noticed potted sunflowers do it, but not sunflowers in the ground. I wonder whether it could be imbalance of top growth and roots - ie the soil is moist, but there isn't enough root to keep up a water flow to match the water lost through the leaves.

In which case, cutting down transpiration would help - keep the air around it a bit more moist - spray it, or stand on a tray of gravel and water.

Or maybe it just doesn't like the temperature - shade it from the full glare of the sun?

you could grow it tall and stand it on the floor :-)