A Brief Introduction to Hydroponic Gardening
What Is It?
Hydroponic gardening is the method of growing plants in a nutrient solution without soil. The functions of soil – providing a source of water, nutrient, air, and physical support – are accomplished by using a variety of soil substitutes such as gravel, sand, sawdust, vermiculite, wood chips, polyethylene sheeting or styrofoam.
Since no soil is involved and the soil substitutes are virtually inert, a plant food can be formulated to give the plant all the required nutrients in the correct proportions, resulting in optimum growth. This means that hydroponic nutrients contain many more elements than conventional plant foods.
How Is It Done?
A simple example of a hydroponic garden is a plastic tray filled with gravel. A drain line leads to a bucket serves as a reservoir for the nutrient solution.
Once, twice, or three times a day – depending on the weather – the solution in the bucket is poured by hand into the tray, flooding the gravel and roots with water and nutrients. In a few minutes this will have drained back into the bucket. The roots do not want to be submerged continuously in the solution, but thrive when exposed to the wet gravel and fresh air which is pulled into the gravel as the solution drains out.
A larger scale, automated unit can be constructed by simply building two wooden boxes. Set one on top of the other, line them with polyethylene sheeting. Place a small submersible pump in the lower box in the nutrient solution and hook it up to a timer.
Fill the top box with gravel. Provide a standpipe to control the water level when pumping and a drain to allow the solution to flow back into the lower box. Set the timer to run as long as required to flood the gravel two or three times daily.
Why Hydroponics?
There are many advantages to a hydroponic garden. It’s clean and easy. No weeds or cultivating. Once set up there is less labor and time required.
It uses less space than conventional gardening and only about 1/30th the amount of water.
Many people today do not have access to a plot of soil. Hydroponic gardens can be set up on patios and balconies.
The yield in commercial hydroponic farms for tomatoes is 12 to 30 times greater per acre than soil farming.
But perhaps the most important reason is the success you will experience. Whether you grow vegetables, flowers or herbs, the quality and consistency of plant’s health and vigor is a source of pride and satisfaction.
Plants can be grown hydroponically outdoors, in a greenhouse, or in a home. But remember, hydroponics does not change a plants requirements for temperature, sunlight, humidity, pollination, etc. A tomato plant is not likely to thrive in a living room where these factors are all wrong. So grow the plants that are suited to your individual living situation.
Practically any plant can be grown hydroponically if you recognize its requirements. Houseplants, fruit trees, herbs, flowers, bulbs, cactus, and vegetables are all possible. Some, however, are more practical and popular than others. Potatoes, artichoke and asparagus are either available in the market at good quality, take too much space or too much time. Tomatoes and cucumbers are most popular, followed by lettuce, peppers, eggplant, cabbage, cauliflower, broccoli, peas, beans, herbs, cut flowers, houseplants, and on and on.
Hydroponics is a hobby that can remain a simple project or evolve into a complex, highly efficient, undertaking. In either case, continue building upon your experience. Read as many books on the subject as you can. Also learn about the plants you are growing. Horticultural knowledge of the life cycle, weather and pollination requirements, pest and disease susceptibility, harvesting and storage tips will add immensely to your success whether growing in soil or hydroponics.
Gravel for Hydroponics
The gravel for Hydroponic gardens is one item that is impractical to mail or ship. Thus the hydroponic home gardener will have t find a local source.
Here are the requirements for a good Hydroponic gravel:
- PROPER SIZE: Particle size can vary greatly, but a minimum size of ¼ ” should be maintained to prevent gravel from entering the drain system, clogging holes and jamming pump.
- CLEANLINESS: Gravel should be clean; free of dirt, dust, debris or foreign objects. Also, it should be free of disease organisms and salt.
- INERT CHARACTER: The gravel should not react with or influence the nutrient solution. Gravel of calcareous (limestone) origin should be avoided. It will cause the pH of the solution to increase, resulting in nutrient deficiencies – especially iron. SEE ‘A’ below.
- WATER ABSORPTION/RETENTION: The gravel should be relatively porous and have some water retention, but not excessively so. Pea gravel is a good example. By contrast, glass marbles would have little porosity or water retention.
- SUFFICIENT WEIGHT: The gravel should be heavy enough to provide adequate support for top-heavy plants when the gravel bed is flooded. Most gravels satisfy this requirement but lightweight rocks like pumice, even if heavier than water, will not provide sufficient stability when flooded.
- DURABILITY: The gravel should not disintegrate or become soft or soggy.
NOTE A: If in doubt, test gravel by washing a sample. Then soak overnight in distilled water and test the pH of the water. Readings above 7.5 should make you suspicious. Beware of gravel that has been exposed to sea water. Avoid coral.
We have found volcanic (lava) or pea gravel (granite) to be the best and most available growing media for the gravel – recirculating hydroponic gardens. However, in some areas some searching and “trial and error” may be required.
For complete information on this subject, refer to Raymond Bridwell’s book, “Hydroponic Gardening” or Howard Resh’s “Hydroponic Food Products”
pH information
The symbol ‘pH’ is the measure of the relative acidity or alkalinity of a solution. The pH scale reaches from 0 to 14 with 7 being neutral.
A pH higher than 7 is alkaline and lower than 7 is acid.
When the pH is too high or too low many nutrients become unavailable to the plants, even though they may be present in the solution in sufficient quantities. Thus the importance of measuring and controlling pH is of significant value.
Generally, most plants do best in a slightly acid solution – a pH of 6.0 to 7.0. To adjust pH use vinegar to sulfuric acid to reduce pH and potassium hydroxide or dolomite lime to increase the pH.