Here's a list of places for supplies:
Tomatofest.com is a great place to shop for organic heirloom tomato seeds
The Drip Store carries automated watering systems, from timers to tubing - at dripirrigation.com -
Home Depot has the best bell pepper plants around - either in Manhattan on 23rd St. or in Yonkers, where they have a big gardening/outdoor section
Whole Foods carries a good selection of organic seeds. We've had good luck with the organic sweet basil seeds
Saiffee Hardware on 1st Avenue and 7th St. in Manhattan carries Hoffman Tomato Food, natural pesticides and more. For a local shop, it's pretty well stocked on pots, cedar planters, and essentials for raising urban crops
Jamali Garden Supplies at 149 W. 28th St, in the flower district, is jam packed with everything from the hard to find but essential Hoffman Tomato Food to decorative items for entertaining outdoors, and it has even better prices.
Union Square Green Market is the place we head each spring for our starter flowers, eggplants and herbs. Sometimes they come with little bugs and pests, so we have to chose carefully!