I have been sowing Datura every year for the past few years as a memorial plant. Because this is an annual I usually plant it in the spring (May) with my other annuals like four O'clocks, zinnias, etc. My preferred variety is Metel White, but I have also sowed the more common Jimson Weed (Lilac). I am way up north where it is still a bit cool in May so I don't know what would be appropriate for your zone. However, I would not sow these in the dead of winter like my hardy perennials. Perhaps a little later will do the trick. These are such absolutely gorgeous flowers, and the scent on the night garden is priceless. I always have to make a conscious effort to remember to go out at night to take photos. I did get this pic. last week.
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Perhaps some one from your zone can give you a more definite response. Good luck.

Datura need warm soil to germinate and moist soil. If you sow them over the winter, the seeds may or may not survive.

A friend of mine who is a farmer, both produce and veggie and flower plants for sale, told me that the chances of the datura seeds rotting in a closed type container that we use for WS is quite high. It keeps moisture in the soil far longer than if they seeds where surface sown, or left to germinate on their own on the ground.

He suggested not sowing the seeds outside before mid April where I live to protect the seeds from rotting and the fact that the seeds will not germinate until the soil temps are about 70 degrees and the daytime temps do not fall to low at night that the soil would drop in temps much lower than 60 degrees.

I've found that sowing in mid April for me, in zone 5, (even though the new zone maps have me in zone 6, I stay with the zone 5 because I am in a valley and a micro climate is around me and Nothing has ever survived the winter for me that is supposed to be hardy to zone 6), has worked well for me, seeds germinate around the 1st to second week in may and are ready for transplant the 1st to 2nd week in June and bloom well for me.

Your zone would have you sowing the seeds earlier, just go by the plan that the soil needs to be about 70 degrees for germination with night time temps that would not drop the soil lower than 60 degrees.

Fran

Thanks northerner_on - beautiful picture. I love the fragrance of the plants!
Thank you also littleonefb - I will sow them later and see what happens.
Always so nice to post on this forum - everyone is so nice & generous with advice!