Gee, Caroline, that's a tough question. Lots of things will germinate but most I can think of would still be tiny.
I grew some Mammoth Sunflowers for a friend this year. I wintersowed them, but they sprouted and grew fast. I WSowed them March 10, and gave them to my friend yesterday. They were 6-8" tall. All least they
looked like big plants.
Most perennials from seed seem to stay small for so long. I can't even think of any other annuals that won't still be pretty tiny in 4 weeks time. Basil grows pretty fast. Maybe big tall zinnias or marigolds? or cosmos? If you pick big tall varieties they at least show growth fast. I imagine you want to share something bigger than 1/2" tall.
Karen
