Planting your own organic vegetable garden is one of the greenest activities around. Just about anyone can do it, whether it’s a few pots on your apartment balcony or a full-fledged kitchen garden that takes up most of your yard. And now is the time to start thinking about it. Even in the far north, seasoned gardeners are hovering over seedlings in their basement or on their windowsill, anticipating that first frost-free date.