Hydroponic gardening is a method of growing plants in a soilless environment. It dates back to the Aztecs, who used rafts covered in soil from the lake bottom in order to plant vegetables, then floated them on the water for the roots to soak up hydration and nutrients. In modern times, it is a popular method for avid gardeners or those who want to condense their growing space for flowers, vegetables or fruit. It's ideal for growing flowers because you can grow them indoors no matter what your climate. Popular choices include marigolds and petunias.
Wet the starter plugs with water in order to create a wet medium for seeds to germinate. Starter plugs are individual cork-shaped plugs that are made out of a sponge-like material with a hole in the middle. The seeds or seedlings are inserted into the holes so that they can grow while the plugs maintain a perfect air-to-water ratio and retain water. They can be found at your local hydroponic gardening store.
Use your thumb to firmly Insert a flower seed into a starter plug. Depending on the type of flower seed, you can put two to four seeds into each plug. Put each starter plug with the inserted seed into the flower flats. The flats are even trays with small empty indentations that can be a couple of inches deep, and resemble the same trays you see at the local gardening stores with seedlings in them.
Keep the flower flat in an area that has direct sunlight. It should get at least eight hours of sunlight per day.
Put a clear, plastic dome over the flower flats, which can be obtained with the flats at a local gardening store or nursery. This dome will help retain moisture and insulate the air around the flower seeds. You want the average temperature to be between 70 and 80 degrees Fahrenheit.
Feed the flowers with a half-strength hydroponic nutrient feeding solution by pouring it into each flower flat, letting the seeds absorb what they need. Depending on the type of feed you purchase, you will need to add about one part water. Read the directions to figure out the exact solution you need.
Remove any weak flower seedlings. After a couple of weeks, you will be able to see the root systems of each flower seed. You want to keep the stronger ones with multiple roots, and weed out the single-rooted or scrawnier ones.
Put the starter plugs directly into the standard hydroponic setup you chose from a gardening store. The flower seedlings should now have root systems that are growing out of the bottom of the plugs.
Continue to add water to the tray (do not pour it on top of the seedlings, just down the sides of the tray) when you notice it falling lower then halfway down the roots.
Continue to keep the trays in direct sunlight, but as they mature, reduce it to five to six hours per day (depending on the variety of flowers, of course). You can harvest the flowers once they reach maturity, when they are about to bloom or already have.