The short answer is that a week of anything now isn't really going to make that much of a difference in the life of the plant. What will make a difference is if you harden the plant off correctly, which means, if you intend to plant soon, you need start hardening ASAP - which you mentioned. My recommendation is that you begin hardening the plants ASAP, and when they are good and ready (don't rush them), then get them in the ground. Assuming that the temps are right for planting, and the plants are hardened, it's almost always better to have them in the ground than in a pot - just make sure they are protected from wind and animals if they are smaller than you'd like. Days to maturity is usually determined by time of transplant, so if you can plant them safely (weather-wise and soil-temp-wise), do that - the sooner the better.

agree with them.. but 2 further thoughts ... if you buy potted plants ... now might not be the best time to be planting... you would probably be better off 'holding them over' until a better planting time in fall ... also ... the plant culture variables are key ... and 'plenty hot and sunny' .. is but 2 of them ... when perfecting this.. you need to take them all into account .. e.g. a plant needs a fully established root mass to pump enough water to offset high heat ... you cant... or shouldnt transplant in heat .. disturb the roots ability to pump water ... and then hope the plant shows no stress ... ergo.. you plant when it cools off ... now is a great time to be thinking about this.. and planning.. but not really the time for action ... ken

Greens like lettuces, Asian greens, kale, chard, arugula and spinach can be pretty easily grown in containers. I grow parsley and other herbs in containers, and green onions too.

I'll tell you exactly what they're like. Two years in a row we had brief temps below 10F in the winter. HIGHLY unusual, but as I noted in a recent post, USDA zones are for general guidance only. Can't depend on them absolutely for any given year. That's why you always buy perennials (trees, shrubs, at least) that can endure a few zones below what you're in. But almost every year we get temps down to 25F. As you should know, USDA zone 9 is rated for 20-25F winter temperatures. That's a hard freeze. In all cases (and I've been growing alliums for almost a decade) they come out of it happy with no protection. Well at 10K they sort of flop, but then pick back up when the weather gets warmer. These hard freezes typically happen in January, and we put in the alliums in November. I think what can hurt alliums is extended periods of hard freeze. Dixondale says explicitly that onion seedlings should be fine down to 20F. There are some varietal differences. Garlic is a rock. Almost impossible to kill garlic with low temps.