Tomatoes

• Hydroponic tomato seeds are more costly than other seeds, but they have been selected specifically for their resistance to certain diseases and their adaptation to controlled environment conditions. Some hydroponic seed varieties include Tropic, Dombello and Tuckcross 520. These seeds yield indeterminate tomato vines. The vines are continuous vine growers, unlike other tomatoes with determinant, bush-like growth. As the vines grow, side shoots are pinched off and the plants are trained to climb trellises. Temperatures within the greenhouse are kept within 60-65 degrees Fahrenheit and should not exceed 80 degrees. Air circulation is necessary in the prevention of disease.
  
  

Cucumbers

• European cucumbers are frequently grown in greenhouses because of their resistance to disease. Some disease-resistant varieties are Silvia, Bello, Sandra, Toska 70 and Farbio. Varieties of American slice and Japanese cucumbers are also grown hydroponically. There are no benefits to growing cucumbers hydroponically but there are no drawbacks, either. If hydroponic growth is your system of choice, then cucumbers will make a good crop; cucumber seed germination rates are close to 100 percent. Plant one seed per container and allow 5 square feet of space per plant if light conditions are good. Allow more space if light conditions are low. Train plants on their own trellises in opposing directions to prevent one plant from shading another's light.
  
  

Lettuce

• Lettuce's shallow root system makes it a suitable crop for hydroponic systems. Successful growers have constructed systems from PVC pipe and sawhorses. Two-inch PVC pipe is drilled with 6-inch holes. Plants are placed in the holes and their roots systems extend into the shallow tubes. The tubes, usually 10 to 12 feet long, are pumped through with nutrient solution. After flowing through the tubes the nutrient solution is recycled. Placing the tubes on sawhorses allows the plants to receive adequate air circulation.
  
  

Floating Gardens

• A floating garden is a practical alternative for those gardeners interested in a hobby hydroponic system rather than a production oriented one. Floating gardens are little more than a wooden frame lined with polyvinyl (a material commonly used for man-made ponds). Children's wading pools and plastic storage containers can be used as well. Frames and containers are filled with 4 to 6 inches of nutrient solution. Tomatoes and cucumbers as well as root crops will not succeed in floating gardens. Instead, plant leafy, shallow rooted crops like mustard greens, mint, kale and lettuce. Some growers have successfully raised sunflowers and zinnias.