Weeds are one of the reasons I don't direct sow. My garden is surrounded by fields full of weeds, so even the containers are hard to keep free of weeds. I have my onion seeds started in my greenhouse right now. And a couple of garlic plants in pots. I'm not sure how well those Mirabilis will do being winter sown. I grow them from seed every year here, and I've never had any volunteers show up the following year.