I have a greenhouse I plant my tomatoes in and I also use a removeable hoop style cold frame too. We've found, for the light frost, that if we can turn on the sprinkler before the sun hits the plants they aren't damaged. That doesn't work with a hard freeze but by that time I generally have all the veggies I need. I have covered the Zucchini just to keep it going a little longer but generally when we get a hard frost it stays cold for a week or so and then we get an indian summer for a few more weeks.

i planted my toms on may 20.and i took this picture when they were 2 months old. started from seed.

Wow, that's great! What varieties do you grow? Do you necesarily grow short season veggies? Where do you guys live? I'd like to hear more when you both have time, Thanks