Having planted in the greeenhouse (heated) in trays opium poppy seeds yesterday from last seasons poppy heads. Should I water them please? and if so how often?
I'm no expert, but I think it's a bit early for opium poppies,and they don't need heat. I'm concerned you'll get lots of early seedling before they can be hardened off to go outdoors.
The compost should be just moist, but never wet, if that makes sense.
I'm sure others will be along later with more advice.
They dont like transplanting. I would scatter the seed outside, where you want them to flower.
Also in regards to watering over the next month or two I always try to avoid watering after noon to avoid the compost being too damp once the light levels and temperatures drop.
I have two "tools" for seedlings of all kinds.
Ist is the bottle top waterer - a tiny watering rose (available cheaply in packs of 2 or 3 from the garden centre). You fit in on the top of a plastic bottle filled with water and it then gives a delicate spray either to souil or new seedlings.
2nd is the seedtray base with no holes in - water into that and then stand the seed tray in it to absorb water. The beauty of this is that new roots are drawn down into the soil to weather the dampness is.
BUT as others have already said the greatest danger to seeds/seedlings is too much water so make sure the soil is barely damp or you'll have problems.
good luck - I'm sure you'll have a garden full of colour in the coming year.
I agree with fidget
I think ordinary poppies need winter cold to germinate, so best to scatter the seed outside in autumn. Assuming opium poppies are the same, I'd scatter them now. Buried seed can survive for decades and grow when the soil disturbance brings it to the surface.