I thought I'd try my hand at some container gardening and decided to
start with Arugula and Mizuna. I direct seeded in late August and
both have germinated well but sent up stalks of about an inch before
the leaves start - which now have been rained on and flattened. Not
that I know any better but this doesn't seem right to me. Shouldn't I
expect bunching at soil level?

From: (Big G)

start with Arugula and Mizuna. I direct seeded in late August and
both have germinated well but sent up stalks of about an inch before
the leaves start - which now have been rained on and flattened. Not
that I know any better but this doesn't seem right to me. Shouldn't

While the seeds do not need much light to germinate, once they have appeared
they should get full light. That is one reason they tend to get leggy it may
not be your case however.