I am a professional plumber and I use home depot for all my supplies, but as a novice gardener, I go to Home Depot too. I feel comfortable there. Their flowers and plants are categorized, Sun or Shade, and come with care instructions. And when that's not enough, I turn to the helpers. They help me select flowers suited for my balcony, and provided tips on watering and repotting.\r
Home Depot guarantees their plants for a year. Why would I buy flowers or plants anywhere else? Just remember to save your receipts and the original pots.