Well- I have have to confess I have let the volunteers grow where they show up many times myself!
I think fall is the time to plant garlic cloves to harvest heads the following year, at least that is how I have been told, and done myself. But I have not planted seeds and tubers in the vegi bed in the fall for spring.
Flower seeds- yes, with limited success. I think hungry critters may be the cause as well as something near to winter rot and our more recent pronounced fluctuating temps causing germination at an improper times during warm "spells".
I do still hope to get around to planting radish- lettuce- spinach in a raised bed or cold frame for fresh harvest this year- mostly just to see if I can- and to enjoy fresh greens!
Please let us know how your experiment turns out if you attempt this this year!

Julie

I work at a CSA farm and we plant garlic in fall and then cover it with straw for the winter, but otherwise everything there waits until spring.

-Marie

Even though some volunteers come up in the spring, I think you'd have issues with temp fluctuations. Maybe some seeds like tomatoes are smart and know when it's safe to sprout!
Peggy