The window for sowing poppy seeds has closed but you could try mid-Spring to get a few to germinate, bloom, and scatter their seeds but I would save most for July/August scattering. My irises from JPW come bare root in April and get planted in-situ; alternatively you could get them in September, which I prefer now that summers are so hot - and the irises prefer
I do grow those irises in much drier areas and they do OK but are spectacular in wet areas; occasional flooding of your hollow might just satisfy them and I think would look so much nicer than the algae
