It really depends on the types of plants you choose.

Perennials are best planted in early Fall, as would be fall/winter annuals.

Spring/summer annuals are planted in spring.

Bulbs such as Iris, Hyacinth, Lily, etc. are planted in the fall for the following spring.

Tubers for tender tropicals such as Caladium are planted in late spring, when the soil temp is above 60 degrees, for the current summer's growth, then dug up and stored for the following year.

As there are not many perennial vegetables out there (though there are many herbs) I would imagine you would treat them as a seasonal annual, but I don't grow veggies so if you wish too I'd check with the Vegetable Gardening forum.