The 501(c)(3) organization does ask for a donation, but it is not required. And you can donate cash, or if you have seeds that you didn't use last year, you can send those along to be passed on to others.
No space is too small for a garden. This year the nine of us are living in a condo, without much gardening space. But I refuse to give up on growing a few things of my own. So it looks like this year it'll be in big pots on my deck and patio.
Find out more about The Dinner Garden here.