You can purchase replacement Wheatgrass and Radish Sprout Seeds on our website here. But you can buy seeds anywhere or experiment with other plants. Just check the back of your seed packet for additional instructions (soaking your seeds is always recommended). You can grow various plants with the Water Garden including sweet potato leaves, green onions, and various house plants. Here's a great article on re-growing produce and herbs you may already have in your refrigerator.
Light is key for growing herbs and greens. During the darker fall and winter months you'll boost plant growth by 1000x by having a grow bulb like this!