By definition, growing hydroponically means a grower isn’t using soil as a growing medium. In fact, the word hydroponic comes from Latin and means working water. The intent and scope of this article is not to provide a concise and complete set of instructions for growing hydroponically, but to provide a general overview of the various steps and processes so novice gardeners have a better idea of what may be involved.
As always, do thorough research on each of the various aspects yourself to maximize your chance for success. All gardening can provide undesired results and experience will greatly increase your chances.
Deep water culture hydroponic growing uses no medium other than water for nourishing the roots. So, with this approach, keeping the water circulating and properly aerated is critical to plant survival. Nutrient levels must also be held tightly at the proper levels for plant vigor, and there is no real room for ignoring the basics. You can’t just walk away from this type of system for several days.
This method, though potentially one of the best for plant yields, may not be for the novice. On the other hand, hydroponic systems that use a grow medium other than water have much more room for error, but represent a great place to start growing hydroponically. Expanded clay, rockwool, perlite, sand or gravel are popular grow mediums for hydroponic growing. The primary difference between using these mediums and soil is that soil will generally hold moisture much longer the others. Letting roots dry out during the normal growth cycle is a sure way to lose them.
For this article, I’m going to use expanded clay as an example. These are the little round balls of fired, naturally occurring clay. They are pH neutral, reusable and don’t compact. So, they keep the same moisture retention parameters over time. They do dry out relatively fast, so you’ll need to be careful when selecting your watering time. Perlite has many similarities to clay pellets but because many of the particles are quite small (clay pellets are relatively uniform in size), perlite can clog emitters. There are some other primary considerations for a hydroponic system using expanded clay, which are:
- There is no need to throw away the old media (as is sometimes needed with soil), so the long-term expense is reduced, and so is the hassle of getting rid of the old media)
- It is lightweight, so it is easier to relocate large pots
- Its numerous, tiny air pockets provide a good source of oxygen and help hold moisture
Preparation of the Grow Media
With expanded clay (as with many other manufactured media), you’ll want to wash and disinfect it before use. You’ll want to do this initially and with each re-use. If it’s not practical to use the grow pots for washing the pellets, find a large container that easily allows flushing and draining.
You’ll need to be thorough to get all the previous roots and old nutrients off when re-using the pellets. Initially, there is just some cleaning of dust and precautionary disinfecting to do. Water is the best for cleaning, just keep washing. High-quality water is better than trying to use some cleaner that your plants won’t appreciate later.
Disinfecting can be done by diluted bleach or hydrogen peroxide. Dilute bleach to 10% and hydrogen peroxide to 3%. Disinfection prevents against microscopic pests in your garden, which don’t really have many natural predators once they infect the system, so making an effort to see there are as few as possible before you start will be well rewarded.
Let the disinfectant stand on the media for at least on hour. Make sure to thoroughly wash off any such disinfectant completely before getting started. Mold can be a more difficult pest to eliminate. Once it is detected, it is often necessary to replace the pellets.
Determining the Correct Watering Cycle for Your Plants
Is your system slow drip or fast? You will need a larger pump and use more electricity for fast drip. These emitters will typically feed at a rate of 5 to 10 gph (gallons per hour) each, and so do not afford as good a distribution of water as a slow 0.5- to 1.0-gph emitter. Because expanded clay pellets will dry out relatively fast, do not have the watering set off for too long a period of time. Avoid growing in areas exposed to moving dry air; this will cause the pellets to dry out prematurely.
Test your watering cycle out before getting started with plants. Popular watering cycles use on/off times of 15 minutes and onwards. Try to avoid an off period of more than half an hour. If using a slow drip system, you can set long watering times (say five hours or more) with 15- to 30-minute off intervals. Slow drip pumps consume little power. The off cycles can extend the life of the pump. A 250-gph pump is capable of watering up to 50 plants where the drip rate totals 1 gph per plant. This rate is not unusual. The timer you select will have a big bearing on your watering cycle.
You’ll want a water application system that does a good job of distributing the water over the surface of the media. Only a drip or two is not going to do well. Ideally you’ll want a drip for about for every 16 sq. in. or more to minimize any dry zones in the media. As the water travels down through the media, it will distribute itself outward through capillary action, so that as it travels lower, all of the media is thoroughly moist. Play with the timer setting to see that you get the best balance of moisture while avoiding intermittent drought conditions. Water will be captured in a reservoir below and then recycled over the media.
If using drip, use an in-line screen to remove debris from the water and prevent plugging of the emitters or aging the pump. The pellets themselves will do quite a bit of removal of particulates. Algae are naturally occurring in water especially where nutrients are involved. An in-line screen or filter can help remove algae, but you’ll need to clean it periodically. Leaving nutrients in the water reservoir create algae and the algae reduce the efficacy of your nutrients. Keep light out of the water tank holding nutrients and clean it often.
Planting and Growing Tips for Hydroponics
Starting plants from seeds is a subject for another article and describing how to do so might take away the focus of just looking at a single type of hydroponic system. Probably the easiest method I know of is to use a rockwool grow cube and incubate it in a humid environment. The water used for new roots needs to be as free from chlorine (or any other toxins) as possible. Using RO or distilled water works, or you can de-chlorinate the water yourself.
If you are transplanting from a soil pot, you will want to gently remove the soil from around the roots and wash with high-quality water. Do not leave soil on the roots of a plant as this can lead to bacterial or fungal infestation and rot. Soil will also plug emitters in a recirculated watering system. Make a cone-shaped moistened pellet area where you lay the thoroughly moistened roots and cover them with wet clay pellets. Begin watering immediately. Avoid allowing new plants to have a dry cycle at all until they have established for at least seven to 10 days.
When transplanting to the new pot, do so as if planting bare root. Using a small net pot is convenient. Place pellets on the bottom, lay your root system over them and add pellets to the top of the root system. When transplanted, the new root system is small and the water applied to the pellets needs to thoroughly moisten the pellets where the roots are. Using a net pot for these roots, and seeing that there are a couple slow drips right on this area, will help.
If you are transplanting from a grow cube, place the cube neck deep in the clay media in a net pot, and then transplant the net pot into your full-sized clay pellet pot. When immersing the small net pot into your grow pot, put your grow pot into a larger bucket filled with water. The pellets will be mostly suspended, making it much easier to insert the net pot into the media at the correct depth, which will be base of the plant—do not submerse the plant! In this example, there are no soil particles to remove before transplanting.
Nutrition Tips for Hydroponics
When plants are young and recently transplanted, high-nitrogen fertilizer is going to stimulate the plant in the wrong way. Nitrogen is what produces foliar growth and new plants need to first grow more roots. So, the nutrient formula you’ll want to use will change as your plants mature.
Often in soil there already exists a considerable amount of macro and micronutrients, but in hydroponic, soilless gardening there usually aren’t any unless you add them. Again, this aspect is not rocket science, but it does require some understanding of what plants need and what different fertilizers to provide to produce healthy, vigorously growing plants.
Summing It Up
Expanded clay requires much of the same considerations that growing in soil does. The method and planning for applying water and recirculating are the most important considerations to make. Once you have a better understanding of these primary parts of growing hydroponically in this medium, you will be on your way towards a successful venture. Take notes during each new crop and things will likely get easier.