Should I be growing my plants using a hydroponic system?
If you are growing or planning to grow plants under LED lighting, then you are probably just as interested in optimising the grow medium as you are the grow lighting. Although plants evolved to grow in soil, they actually only need the dissolved mineral nutrients that are found within it ... and that's where a hydroponic system comes in. Hydroponics is a technique for growing plants where the soil is replaced by an optimised concoction of nutrients that has been specifically formulated to cater to the needs of plants.
Unlike soil, which can vary widely in nutrient levels, hydroponics provide a much better way of precisely controlling the amount of nutrients plants are given so that their growth can be optimised. Hydroponics also allow one to do a whole lot more with a whole lot less. Space is something that is always very important to us indoor gardeners and especially to those of us in the UK where any floor space is always at a premium. Hydroponic systems are far more productive per unit area as plants grow far more efficiently in nutrient solution than they do in soil. Since all the nutrients that a plant needs are readily available in an absorbable form, they also don't have to grow as large a root network to ensure that they get enough of their required nutrients. This means that more resources are available to grow the part of the plant that is 'above ground'. It also means that you can get more out of your plants in a shorter period of time, permitting edible-plant growers more harvests per year than the equivalent soil-based set-ups.
Together with grow lighting, hydroponics is also ideally suited to multi-level set-ups where the nutrient solution is able to flow 'down' the system. Hydroponics performed under the right conditions (ie. within grow tents or a grow room with bug nets on the air intakes) can also pretty much do away with pesticides. Finally, the other great thing about hydroponics is that even though the system is based around water, it actually only uses a tenth of the water that plants normally use when they are grown in soil since hydroponic systems continuously recycle the nutrient solution with very little waste, making it kinder on our water bills!
So if it is so much better then soil-based growing, why aren't more people growing hydroponically? The foremost reason is the upfront cost and difficulty of set up: it is far cheaper and easier to throw some soil into a pot, plant some seeds, and let nature take its course, than it is to figure out, learn about and part with your hard-earned cash on specialist hydroponic equipment. The thing is, over time (and if you are a committed indoor gardener like ourselves), it WILL work out to be cheaper to grow hydroponically, and once you've dedicated a little time to understanding how hydroponics works, you will probably save time in the long run not having to deal with all the inefficiencies associated with soil-based gardening!
So you may be wondering whether your specific plants can be grown in a hydroponic system, well fortunately, that's an easy question to answer. If your plants can grow in soil, then they can almost certainly be grown hydroponically. It's just sometimes a matter of getting the right hydroponic system that is best suited to your plant type. Some plants are relatively easy to grow and do well in all hydroponic systems. These include salad greens (lettuce, spinach, etc) and herbs (eg. parsley, basil, mint). In the case of tomatoes, cucumbers, peppers, and chillies, they too will do well in almost any hydroponics growing system as long as they get copious amounts of light - think LED grow lights! 🙂 However, some plants like root vegetable-type plants (eg. potatoes), berries, and bulb-type flowers do better in some hydroponic systems than others. So let's take a look at the different systems available.
Hydroponic Systems available in the UK
As with any other technology, there are a number of equipment variations that one can adopt when setting up a hydroponic system, but all of them pretty much fall into one of two main categories: either the plant roots are 'suspended' in a constant flow of nutrient solution without any supporting medium (other than the starter media used in plant propagation), here referred to as 'water-based hydroponic systems', or they use an inert medium in which the roots of the plant grow with the nutrient solution trickling through it, a so-called 'medium-based hydroponic system'.
Water-based hydroponic systems in the UK
The most commonly-used water-based hydroponic system is the Nutrient Film Technique or NFT which usually does not employ any medium for root growth. These systems are composed of some form of channel in which the nutrient solution, having been pumped into the top of the system, flows back down into the reservoir in an endless cycle. Plants that have well developed root systems are then usually placed in some form of a holding 'basket' with their roots 'dangling' down into the nutrient solution.
For young plants, that have yet to develop a sufficient root structure, rockwool cubes or similar propagation starter media in which the seedlings are first grown, are often placed just at the nutrient solution water line to allow the cubes to become moist. This encourages the baby plant to grow roots down out of the starter media and into the nutrient solution.
For the home grower, the SureGrow NFT hydroponic system is similar to what most professionals use and what one usually sees on TV when the subject is about hydroponic farming but on a small scale. It comes in a range of sizes to cater to your space restrictions and number of plants required, and can be purchased either as a complete system (see table below) or as 'add-on' units, which can be useful for future expansion of your hydroponic set-up (the tanks hold sufficient volume to allow one add-on unit to be attached). The mesh pots that come with the SureGrow system have snap-on lids to minimize light exposure of the nutrient solution and the pots are also designed to be easily lifted, which is useful for root inspections. One point to note is that although this is officially a medium-free system, professionals usually fill the mesh pots with a little coco or clay pebble media to physically stabilise the starter media containing the seedling or cutting especially if the starter media is much smaller than the mesh pot.
SureGrow NFT hydroponic systems
Another UK company, Nutriculture, also makes a simple but versatile NFT hydroponic system that is different from the typical NFT hydroponics set-up and is also specifically designed for the home grower. Instead of independent channels for nutrient flow as with SureGrow-type systems, Nutriculture NFT systems have multiple channels embedded in the bottom of a tray on which plant pots or rockwool cubes or similar starter media containing the plants are placed. The tray sits above a reservoir of nutrient solution which is continuously pumped into one side of the tray, flows through the channels before falling back into the reservoir. Conveniently, they also come in a range of sizes so that you can simply get the system that fits your requirements and the space you have available (see table below).
Nutriculture NFT hydroponic systems
Medium-based hydroponic systems in the UK
Ebb and Flow (also known as Ebb and Flood) hydroponics: These systems contain an inert medium that mostly provides physical support to the plant roots. At regular intervals, the root-filled medium is flooded with nutrient solution which then, through the action of gravity, slowly drains back into the original reservoir whence it came. Ebb and Flow hydroponic systems can be used for plants at all stages in their life cycle, but are particularly useful for small plants since the medium provides structural support for young plants and their developing roots. The simplest and most robust Ebb & Flow hydroponic system that you can get in the UK is also from Nutriculture. In the Nutriculture Ebb & Flow system, plants are grown within an upper tray containing the medium itself or the individual pots containing the medium, depending on preference. The upper tray sits atop a separate reservoir of nutrient solution which is then pumped into the upper tray from an opening at the bottom. The upper tray contains channels to ensure even distribution of nutrient solution as soon as it enters the upper tray. Gradually, the nutrient solution trickles back down into the lower reservoir ready for the next feeding cycle.
Nutriculture Ebb & Flow systems
Drip hydroponic systems: A slight variation on Ebb and Flow medium-based hydroponics is the Drip system. This works in a similar fashion to Ebb and Flow systems but instead of flooding the medium from below, the solution flows into the upper tray from openings placed above the medium. The nutrient solution is then free to trickle through the medium back into the nutrient solution reservoir. This system is even more suited to young plants that are still developing their root network, as the solution is 'guaranteed' to pass over even the smallest root network. Once again Nutriculture appears to have the best all-round system for this type of hydroponics (see table below) - (btw just in case you are wondering, we have no association whatsoever with Nutriculture, they just seem to have the most appropriate systems for the home grower in the UK!).
Nutriculture Drip systems
Another drip-based hydroponic system is the Wilma system that has been developed through a collaboration between ATAMI, a Dutch company that specialises in plant nutrient media, and Nutriculture, a British hydroponics company. As with other hydroponic systems, periodic plant feeding from the Wilma system leads to higher oxygen levels around plant roots, which in turn leads to better plant growth and higher yields than more conventional growing methods.
The Wilma system consists of three major elements: the main reservoir, the electric pump and water distribution network, and the pots that hold the individual plants. A timer (not included) is needed to operate the pump at the required times, usually between 1-3 (depending on the type of inert media used), 15 minute feeds a day are required for young plants, with the number of feeds increasing for adult plants. There are several different size formats that the Wilma system comes in with both reservoirs and media-holding pots varying in size, and with some interchangeability between the different formats. As a consequence, the naming system used for the different Wilma systems is a bit confusing. In general, the type of Wilma system is indicated by the reservoir size first, followed by the number of pots and their sizes. Reservoir sizes come in Small (30L), Large (50L), XL (70L), XXL (150L), Small Wide (85L), Large Wide (120L), and XL Wide (180L), and the individual pots are available in 1.65L, 6L, 6.5L, 11L, 18L, and 25L formats. So for example, a Wilma Large 4 pot 18L system consists of a Large format (50L) reservoir, with four 18L pots sitting on top of it.
One of the nice things about the Wilma system is that it is compatible with just about any hydroponic substrate, including very absorbent substrate like Coco coir, as well as with non-absorbent inert media like clay pebbles. Both types of substrate can be used in the Wilma system so long as the correct dripper stakes, which are included as part of the system, are used, with the flood drippers designed for media with high levels of drainage and the arrow drippers for substrates that will retain water for longer periods.
Another well-thought-out feature of the Wilma system is the integration of a mixing tap, which precludes the need for mixing up nutrients before adding them to plants. Instead, individual components of the nutrient system in use can be added directly to the reservoir in the correct amounts and the system can be run with the mixing tap in the closed position. This allows the pump to circulate the water in the reservoir without it reaching the plant-containing pots, and eliminates any risk of exposing sensitive plant roots to damaging high concentrations of nutrients.
Nutrient monitoring in the Wilma system is also easy, with a large diameter red-capped access point located to one side of the reservoir. This allows for nutrient volume and pH levels to be monitored regularly and adjusted as necessary all without disturbing any other elements of the system.
On the more negative side, as with any drip-based system, Wilma included, there is always the risk of the water distribution lines becoming clogged, usually from the precipitation of the relatively high salt concentrations found in nutrient media. This can mean that plants don’t get the feed they need and there would be little indication that anything was wrong until it was too late and the plants begin to show its effects. Consequently, the Wilma system, although automated for the most part still needs to be carefully monitored and cleaned periodically to ensure that the nutrients are flowing freely to each pot.
Wilma Drip systems
For a detailed breakdown of how to set up and operate the Wilma system, One Stop Grow Shop has put together an excellent video which is well worth watching if you are in the market for such a hydroponic setup.
Hydroponic Supplies and Accessories in the UK
There are a number of components to any hydroponics growing system, and with several different types of hydroponic set-ups in existence today, means there are a whole range of different hydroponic supplies and accessories that are available to fit each system. As a consequence, talking about the subject as a whole on a single page is insufficient and we have split the topic across multiple pages. Immediately below, we focus on the types of inert media available for media-based hydroponics systems, while specfic information about other hydroponic supplies and accessories available in the UK are linked to at the bottom of the page.
Inert Media (for medium-based hydroponic systems)
There are several media on the UK market that can be used with medium-based hydroponic systems (Ebb & Flow set-ups and Drip systems). The four main ones that are most often used are shown in table below. All of them will work to some extent but you will have to do a bit of trial-and-error to identify which are working well in your hydroponic system. For example, if you are using a drip-based hydroponic system and the 'dripping' happens to be slow, then you will need a medium that retains water for longer as the nutrient solution may be draining away faster than it is being added. Often more experienced hydroponic horticulturists will use a specific mixture of different media to achieve the desired aeration and drainage properties that they need.
The most commonly-used hydroponic medium around are clay pebbles which you often see used on display in garden centres and gardening stores. The clay pebbles are reusable so can be quite economical but they will have to be cleaned and sterilised after each use. Less common media include coco, perlite, vermiculite, sand, gravel, growstones, and others. The 4 best ones appear to be clay pebbles, coco, perlite and vermiculite. Clay pebbles and perlite exhibit excellent aeration and drainage properties compared to other media, whereas coco and vermiculite tend to retain water more and have the added advantage that they absorb nutrients for later use by plants. Unlike clay pebbles however, perlite is very light weight and often needs to be stabilised with a denser medium to prevent it from floating away, especially in Ebb & Flood hydroponic systems. 50% perlite / 50% vermiculite or 50% perlite / 50% coco are mixtures that tend to give the right combination of aeration and drainage properties for many hydroponic systems, but ultimately you will have to experiment to get the right one for yours.
The reusable clay pebbles are sterile and ready to use out of the bag. However, when it comes time to reuse them, they will need to be cleaned and sterilized. A 10% bleach solution followed by copius rinsing in clean water should be sufficient. Even though 'clay' sounds heavy, it is actually quite light and does not compact with time unlike other media. Consequently, the clay pebbles exhibit better aeration and drainage compared to other media.
Coco naturally contains the trichoderma Fungi, which is known to protect roots and stimulate their growth. Coco drains readily and holds just the right amount of air and water for healthy roots. Consequently, plant roots grow very readily in coco. Coco also tends to capture minerals from the nutrient solution and release them to the plants over time. Coco can take different forms, so dont be alarmed if your coco does not look exactly as in the picture. The most common form is known as coco peat, which looks a lot like soil but is in fact completely inert.
Perlite is actually often used with the next medium on the list, vermiculite. Perlite is very light weight and often needs to be stabilized with plastic netting or similar to prevent it from floating, especially in some Ebb & Flood hydroponic systems. This is also a reason that it is often used in conjuction with the denser vermiculite.
Vermiculite is very similar to perlite, and is often used in combination with perlite due to some complimentary properties. Vermiculite tends to retain more water than does perlite. Vermiculite also tends to retain more nutrients from the nutrient solution than perlite, releasing them slowly over time.
For information on media used for seed-starting and plant propagation in hydroponics, see the Seed Starter Media page.
For information on nutrient solutions used in hydroponics, see the Nutrient Media page.
For information on pH meters used for hydroponics, see the pH Meters page.
For information on EC and TDS meters used in hydroponics, see the EC (TDS) Meters page.
For information on Reverse Osmosis (RO) water purification systems, see the water purification systems page.