The Hydroponic Greenhouse

Greenhouses are used by many traditional gardeners and they also offer a good alternative to the hydroponic gardener as much of the same advantages apply in either setting. Hydroponics is, in fact, especially suited to greenhouses, because light, temperature and airflow are easier to maintain than in some other settings. If they are in a good hydroponic greenhouse fruits and vegetables such as strawberries, peas and many others; thrive – and flowering plants such as orchids are particularly suited to this type of environment.

Proper light control is one of the more challenging aspects of hydroponics because the medium in which the plant grows is obviously kept wet. When the medium is itself water, algae growth can be a problem. In a greenhouse it is easier to keep light from reaching under the surface; in addition to this the amount and angle of the light can be more easily controlled with shutters and shades etc.

Just like their soil based siblings hydroponically grown plants need ample light to grow well. Greenhouses don’t produce more light by themselves; rather they filter and diffuse it which keeps the interior warm and more uniformly lit. Greenhouses protect the plants from the cold exterior while at the same time letting in needed sunshine.

Many northern countries have low temperatures in the winter but several hours of sunshine daily – investing in a translucent polycarbonate greenhouse wall can easily keep a greenhouse at 100F/38C even in winter temperatures of 15F/-9C. It is also easy to install vents with fans which will keep the greenhouse from getting too hot. Temperature control for hydroponically grown plants is just as important, if not than it is for soil-based situations.

Utilizing a greenhouse to ‘keep the benefits and exclude the harm’ gives the hydroponic gardener the best of both worlds. Without a greenhouse the only alternative might be using the inside of the home – and for some people this can be a big disadvantage whereas a greenhouse, among other things, can provide a superior lighting and watering system arrangement. Few homeowners will want to give over a room to high pressure sodium or metal halide lamp fixtures and not everyone will want drip irrigation systems running through the spare room.

With a greenhouse elaborate systems can be placed in the precise position that is best for the plants; which is more convenient for the gardener. Convenience is of particular importance in hydroponics, since light and water amounts are more critical than they are in soil-based gardens. Soil-based gardens tend to be more self-regulating and without the need for special setups – even so it is easier to arrange nutrient feeding systems in a greenhouse. When it comes to hydroponically grown plants this is critical. Given reasonably good soil, plants will simply extract what they need and exclude what they don’t. In a hydroponic setting that has to be arranged by the gardener.

pH control offers the same problem and greenhouses the same solution as it is much easier for the pH to shift in a hydroponic garden. Because water is ever present acidity and alkalinity can change rapidly by large amounts and ions flow more easily in these circumstances. Working in a greenhouse allows the gardener to set up automatic pH control systems to reduce the amount of manual adjustment needed.

Greenhouses can be constructed or purchased ready made and they are an excellent investment for anyone interested in hydroponics.

Hydroponics Really Simple Plant Biology

Hydroponics is essentially a branch of horticulture or the practice of cultivating plants. Before one can cultivate well however, it is essential to have some knowledge of what plants need – and this is where botany comes in.

Some people are intimidated by the phrases ‘plant biology’ or ‘plant physiology’ and even the word botany. Certainly these sciences can be very complex and studying them is reserved for someone who is truly motivated or is a botanist by profession. However, even those who garden ‘by the seat of their pants’ can benefit from a small amount of such information, and it doesn’t have to be difficult to absorb.

Plants are living things but there is an important difference between plants and animals. Chief among those is a plant’s ability to absorb nutrients and generate what it needs – it does this by absorbing sunlight, which provides an energy source. At the same time, a plant can extract available chemical elements from the surrounding medium and transform them into food for itself.

Animals, on the other hand have to get their food from other sources, such as plants and other animals. Sunlight provides animals with warmth but not the energy to power their functions – however, there are exceptions as in all biology. Some extremely small organisms that are sometimes thought of as animals can perform plant-like activities and this makes them borderline cases.

The primary mechanism that most plants use to perform needed activities is photosynthesis which can be represented by a simple chemical equation:

6CO2 + 12H2O + light = C6H12O6 + 6O2 + 6H2O

Six molecules of carbon dioxide (6CO2) and 12 molecules of water (12H2O) combine by using energy provided by light. The chemical reaction produces glucose (C6H12O6), a type of sweetening agent. As with animals, the glucose is then later broken down to provide energy for various functions – a ’side benefit’ to the gardener is that six molecules of oxygen (6O2) and six of water (6H2O) are given off.

That relatively simple chemical reaction allows plants to be self-sufficient. They take in available energy, pull nutrients from their surroundings and produce their own energy and food. It would be great if humans could do the same! However, there is more to the plant’s life than energy production and food consumption. In order to perform those functions plants have to be sturdy and able to breathe.

In order to carry out essential processes, the plant needs a stable structure. Since hydroponics is soil-less, that support has to come from somewhere. Externally it is supplied by the medium which can be supporting trays, strings, or rockwool, etc. Internally, the plant’s own cells provide that support, using available elements.

Calcium, for example, plays a large role in forming a plant’s cell walls these eventually build up into tissues that form different types and enable features that stand up to gravity, wind and other forces.

Plants, like animals, perform a kind of respiration – breathing. Many of us are taught in elementary school that plants take in carbon dioxide and give off oxygen. That’s true. But they also consume oxygen. They simply give off more than they consume.

Plants don’t have lungs of course, but they do have stoma (pores or holes) that allow them to take in CO2 and oxygen and expel some of the O2 and this process is called cellular respiration which is essential to root growth.

Preparing Your Hydroponic Garden

Hydroponics is fun experimenting with different plants grown in water or rockwool leads to a new appreciation of the factors required for them to thrive. With any successful project however, a certain amount of preparation is required.

The first, and most obvious thing needed is the plant itself, either in the form of seed or a pre-existing plant. Luckily, and with the proper care, nearly any plant can be grown hydroponically. Tomatoes are a favorite starting plant for those new to hydroponics. They drink up large amounts of water anyway and can grow to enormous size in containers without soil.

Since hydroponics doesn’t use soil to support the plant as it grows, some substitute has to be found. Water is the most common medium, but it won’t support a growing plant against gravity. The hydroponic gardener uses a number of different methods instead.

A small container with proper supports for the stem will do well – hose supports can be as simple as wooden ice cream sticks or plastic straws glued to the container or secured with string. There are also kits are available that will supply all the structural components the novice hydroponic gardener will need.

The container size will vary depending on what it is intended for but a good first try will be about 6-12 inches deep and 2-3 feet wide. A smaller container will work with smaller plants or gardens – but even a single tomato plant will require room to grow, so better to overestimate than start out too small. Transplanting is a more advanced activity that should be reserved for later.

Fill the container with water and reserve non-aqueous methods such as perlite or rockwool for later when hydroponics cultivation has become more familiar. Start with clean, but not necessarily distilled, water; plants in fact, grow better in water with minerals. However, the water you use should be free of organisms you can sterilize or microwave it to be certain.

The water will have to be aerated because plants grown in water still need to get oxygen from the medium for cellular respiration in the roots even though photosynthesis consumes CO2 and gives off O2. However, plants use up any dissolved oxygen quite quickly and this means it has to be added artificially. An aquarium pump and filter will do the job, but one designed specifically for hydroponics is best.

As with most plants, light is essential; there are some exceptions, of course – not all plants need to photosynthesize. Most plants will require 8-10 hours per day of intense light and that is best supplied by natural sunlight. It is possible to substitute, to a considerable degree, with artificial lights and sodium lamps and other types made especial for hydroponics are available.

Plants need nutrients. A good supply of NPK (Nitrogen, Phosphorus, Potassium) fertilizer with certain trace elements is fine but you should look for those with the right percentage for growing in a hydroponic setting. Too much nitrogen, for example, can easily burn a plant living in water just as it can burn soil-grown plants. Pre-mixed solutions are the easiest to work with, but you need to ensure that they contain roughly the following elements or compounds:

Substance	Amount (per 25 gallons of nutrient solution)
Potassium Phosphate	1 tsp
Potassium Nitrate	4 tsp
Calcium Nitrate	7 tsp
Magnesium Sulfate	4 tsp
Boric Acid	1/2 pint
Manganese Chloride	1/2 pint
Zinc Sulfate	1/2 tsp
Copper Sulfate	1/2 tsp
Iron Sulfate	1/2 pint

Some water sources may already have some of these and water testing kits will help you ensure you have the right compounds and a close to neutral pH. You need to be prepared to change the solution about every two weeks.

A means of keeping the water at the right temperature is vital as most plants don’t grow well in continual cold and that is especially true of tomatoes! Unless the climate supplies all the warmth the plant will require a heating element is essential. You will also need a thermometer to measure the temperature.

Once you have your plants and the materials to support and care for them, then being a hydroponics gardener is just a matter of a little bit of research.

Plant Nutrient and Feeding Guidelines

All plants need nutrients to supply them with the elements needed for vital biochemical processes. Nitrogen (N), phosphorus (P) and potassium (K) are the top three that are generally listed, but there are more than a dozen others. Magnesium (Mg), iron (Fe), calcium (Ca) and several more perform essential roles in the life of hydroponic plants, just as they do in soil-based gardens.

Nitrogen is used by growing leaves; but despite the fact that the air is about 79% nitrogen, plants need it in the form of a supplement. The N2 molecule in air is very stable and plants don’t need to break it apart to use single nitrogen atoms. Phosphorus is essential to root growth and owing to its role in enzyme formation potassium aids in disease resistance.

There are other elements which perform a variety of functions to aid growing plants. Calcium, for example, is a large component of cell walls and also helps to deliver ions to various parts of the plant. Chlorine (Cl) is a component of chlorophyll and an important participant in photosynthesis. Iron is essential to the hemoglobin molecule, which is formed in plants as well as animals and it helps to transport the oxygen needed for cellular respiration.

Pre-made solutions are the easiest to work with when it comes to supplying all the elements that plants need. Dosage is important as it is with any compound. For very young plants, such as small cuttings or those that are just germinating, 1/3 teaspoon of calcium nitrate dissolved in a gallon of water is about right. Plants that are flowering will require more, about 3/4 teaspoon of calcium nitrate.

Water and temperature conditions are important factors when it comes to feeding your plants. Any solution should be applied at room temperature and this should also be the temperature of any water used in hydroponic gardens.

Dry plants should not be fed nutrients as it is possible for them to be burned by the nitrogen. However, this is rarely a problem with hydroponics, although one ‘branch’ which is known as aeroponics, where the plants are grown in air, can suffer that problem.

Allowing any water to stand overnight will help to evaporate any excess chlorine from home water sources. Mineralized water is preferable to distilled water for this purpose as it will contain calcium and other useful elements.

Regulate the pH to keep it as near neutral as possible. As plants take up nutrients they’ll tend to make the water alkaline. Add tiny small amounts of sulfuric acid to move it back to neutral. Sodium hydroxide will help shift excessively acidic water back to a neutral pH.

Hydroponically grown plants are more sensitive to nutrient levels and less able to self-regulate than those in soil-based gardens. In soil, for example, they can take up or shed compounds. Releasing compounds into the water medium doesn’t move them away from the plant. The hydroponic gardener will need to exercise more care to keep plants healthy.

Lighting the Hydroponic Garden

Most plants that are grown in a hydroponic setting require light, lots of it. This is because they photosynthesize to produce their own nutrients. They require warmth, not only to keep biochemical reactions going but to keep it going at the right rate. A hydroponic setting regulates many processes by the amount of light present, speeding some up and shutting down others.

During photosynthesis plants take in carbon dioxide and water to produce glucose and oxygen. The glucose is used as an internal energy source and much of the oxygen is expelled; but the color and intensity of the light they receive plays a large role in how plants do that.

The fact that leaves are generally green and/or yellow shows that those colors are being reflected. The other components of white light (which is a mixture of many wavelengths) are mostly absorbed by plants – but some are taken in more efficiently than others at different growth stages. The wavelengths that we perceive as red in the spectrum range are used more during growth phases. Blue on the other hand is absorbed more to produce flowering or fruiting.

Since few hydroponic gardens are simply left out in the sun to take their chances, a lighting scheme is required to assist them in all those activities. Plants that sit near an open window or which are grown outdoors largely self-regulate the wavelengths they absorb, where the whole spectrum is abundant. On the other hand plants that live indoors can only take up what is available – this makes it important to ensure that they have all they need, both in terms of intensity and wavelength.

Indoor lights are typically less intense than natural light as they provide less overall energy and therefore plants may need to be supplemented with natural light. In some cases it may be necessary to use special lights to provide the total amount of light energy needed for warmth, photosynthesis and other useful tasks. However, the mixture will vary from one climate to another.

Indoor lights come in a variety of types, prices and wavelengths, some are better than others for plants. Incandescent lights for example provide a lot of heat – and this is the reason that they are relatively inefficient in electricity usage. However, incandescents at the red end of the spectrum produce strongly while they produce a lot less in the blue range.

In contrast to incandescent lights many fluorescents tend to produce greenish light. This is because they are filled with mercury and the interior coatings that produce light in the visible range may be better or worse at producing a white-approximating spectrum. However, in the long run these are much cheaper to use.

A relatively inexpensive setup can be achieved with a mixture of incandescent and fluorescent lights. A 30-watt incandescent with a 100-watt equivalent fluorescent provides a good balance of wavelengths – fluorescents use much less electricity so the wattages can’t be directly compared.

Metal halide and sodium lamps make for very good lights for hydroponic gardens even though they are more expensive. Metal halide lamps produce well in the blue range and sodium lamps provide more reddish light. The bulbs can’t be switched between fixtures so it is necessary to buy a housing fixture that is appropriate to each type.

Some newer LED lamps will produce a very broad spectrum and some can be adjusted to favor one wavelength range. However, they are expensive and many will not produce the same output as other types. In addition to this plants vary in the intensity of light they require; you should try to ensure that medium light plants receive at least 1,000 foot-candles while others will need 2,000 foot-candles (about 20 watts per square foot) or more. A good light meter will tell you how much is being given off, or you can sometimes find the rating listed on packaging or advertisements.

Plants that receive sunshine will need from 8-10 hours per day. If only artificial lighting is used, the number rises to between 12-14 hours per day. For some plants and lighting schemes 16-18 hours per day may be needed as the specific number depends heavily on the type of plant.

Hydroponics Growing Media

Plants grown in a hydroponic setting require support and water just like any other plant. As a result of its name; many people who are new to hydroponics might be forgiven for thinking that plants are always grown in water. This is certainly done, but there are many other choices og media. Hydroponics is really just soil-less plant growing, with some other substance which provides the support and nutrients fed in ways other than through earth.

Using Rockwool

One of the most popular choices is a material called rockwool. This is a type of basalt that is specially processed to provide a strong, porous base. It is mostly inert, so it won’t decay or leach compounds into the water very much. Since it is porous, it provides good drainage. Rockwool is also lightweight and inexpensive.

Rockwool cubes are often used but small slabs are also available. There are pre-drilled holes in that allow for placing and growing seeds – any cubes containing plants that don’t survive can be easily removed. The cube can be cleaned and replaced with another seed to try again, or simply left out to provide additional space for the survivors. This way, the hydroponics tray can be regulated easily so that there are a limited number of plants competing for air, light, space and nutrients.

Despite its lightweight and porous nature, rockwool provides a very sturdy medium for growing plants. It gives good support to developing roots. At the same time it helps regulate the water temperature as it is a good heat conductor. Adding rockwool will alter the pH of the environment slightly at first, but this is easily controlled using a pH kit.

Though rockwool has many advantages for a hydroponic gardener, most people will want to experiment with different media at some time and there are a number of options available.

Using Sand

Ordinary beach sand is one common medium and it drains well compared to ordinary clay-infused soil. In a hydroponic setting however, it doesn’t do as well as most other possible media on the other hand it is extremely easy to use and certain plants take to living in sand very well. Certain orchid species in the wild, for example, grow naturally in wet sand.

Using Gravel

Ordinary aquarium gravel is used in some settings as it provides a strong, clean supporting medium that can also be attractive. But it can crumble and this means it will have to be cleaned and filtered well before use. Because it’s very heavy, a good pump will be required to keep air and water flowing through the system properly – otherwise, plant roots may dry out.

Using Perlite

Perlite is a more popular alternative than gravel. It is a type of volcanic rock that is heated to form small, lightweight pebbles resembling glass beads. Perlite is popular because of its ability to retain air. Since hydroponically grown plants will quickly deplete any dissolved oxygen, perlite will help the pump keep the water oxygenated.

Using Vermiculite

Vermiculite is similar to perlite as it is also made into small pebbles to provide a flexible supporting medium for hydroponic plants. It draws in water from passive systems by capillary action, and this in turn helps to automate the watering and nutrient feeding tasks. Since it holds even more water than perlite it may exclude air so it needs to be used in moderation. For this reason many people will use a mixture of perlite and vermiculite. If you are new to hydroponics then experimenting with different options can provide a lot of fun.

Hydroponics – All about pH

pH or the relative degree of acidity or alkalinity, is a vital component of a plant’s environment as the pH changes the ability of the roots to absorb nutrients changes. However, in order to understand pH and what to do with it, it is helpful to have some elementary knowledge of chemistry.

pH is a measure of the relative concentration of hydrogen ions or hydroxyl ions. They are called ‘ions’ because they are electrically charged. Hydrogen ions are positively charged while hydroxyl ions are negatively charged.

The standard pH scale runs from 1-14. Numbers below 7 and nearer the 1 are more acidic (relatively more hydrogen ions), those higher than 7 and toward 14 are more basic or alkaline (more hydroxyl ions). Exactly 7 is neutral, no ions or a balance between acid and basic. Any free hydrogen (H) and hydroxyl ions (OH) will tend to combine to form water, H2O.

Hydroponically grown plants will do well in a near-neutral environment and most plants thrive in slightly acidic conditions of 6.0-6.5. Apart from the chemical state in the roots themselves, nutrient solutions need to be fully dissolved into the growing medium (often water), so that they are more easily absorbed. A highly acidic or basic environment interferes with that. However, with easy to use kits it is now relatively simple to control the pH level. There are different types of kits but two of the most common kits include a bottle of solution and a container of powder respectively – each of these has good points and bad points.

With dry powder kits you need to make up a solution before you can feed the plants; the powder is concentrated but the setup is best when the material is in liquid form – if it is not sufficiently dissolved then inevitably the application is uneven. On the plus side powder kits are cheaper than solutions; they store well and providing they are kept sealed; the material will last a long time.

Solution kits may cost a bit more, but they are ultra-easy to use. You just measure out the exact amount, which is a little easier with solution than powder, and dilute or apply it as it is. Kits vary; many are highly concentrated solutions while others are premixed at the right concentration in the bottle. Before you can judge how much of a solution you should apply you first need to know what the plant’s environment is at that time. This is made easier with a pH testing kit.

Older testing methods are still available and often consist of simple colored strips. The paper strip is dipped into the plant’s medium and an embedded dye makes the strip change color – the color is then compared to a chart to gauge the pH level.

By contemporary standards this is a fairly inaccurate way to judge pH; as you can imagine. Today digital meters are the most popular means and these are generally more reliable than the strips. They do, however, need to be cleaned between tests to maintain accuracy whereas the paper strips can simply be thrown away.

Whatever kit and testing method you choose, it is essential to keep the plants’ pH near optimal levels. The difference between 6.0 and 5.0 in a pH level represents ten-times the difference in the concentration of acid present – and with pH levels, small numeric differences matter.

Growing with Hydroponics – Soil-less Plant Culture

The name hydroponics refers to plants grown in water rather than soil. Basically the word covers any method of horticulture that often takes place in an artificial setting and doesn’t use soil. This method is also referred to as soil-less controlled environment agriculture or S/CEA.

While hydroponics has many benefits both to the plant and the gardener it also has its challenges. Using this method makes controlling the amount of water and nutrients that reaches the plants is more difficult. Light control is more important with hydroponics than with more conventional methods and pH adjustment is critical. These are mostly factors that are self regulating in a soil-based garden. The gardener has to take some extra care when using hydroponic methods.

On the plus side; and given the right conditions hydroponics actually yields larger fruits and a larger output overall than traditional methods – this is because hydroponic methods use less space to accommodate larger plants and this results in a greater yield. It is actually easier with hydroponics to achieve a greater yield with less effort than normal. In a typical hydroponic setup for example, weeding is much less of an issue than it is when the plants are in soil. In a soil-less environment it is much harder for the weeds to get started and they are more easily killed off when they do. However, achieving such benefits depends to a large extent on the arrangement of the hydroponic setting.

It is much easier to achieve the right environment and arrangements if you use a complete hydroponic kit – these kits come with trays and tubing, nutrients, lights and air pumps as a starter; some kits also contain seeds. Hydroponic kits are especially good for the novice because they contain all the ‘ingredients’ needed to start a hydroponic garden. The kit also includes the knowledge that a beginner needs to start this type of garden.

However, a kit-housed hydroponic garden needs as much care as any other. The right nutrients have to be fed to the plants and even if the kit contains an automatic feeding system this will have to be set up, filled and checked. You will also need to build or arrange for automatic watering systems, like drip irrigation or under-the-tray tubing. All of the above components need regular monitoring for fungi and then cleaned or sterilized.

Just as pest and disease control are part of traditional gardening; so they are in hydroponic gardens. Constant moisture provides a fertile environment for bacteria, mildew and other harmful organisms. You will also need to deal with white flies, aphids, spider mites, caterpillars and other common garden pests. Luckily there are plenty of easy to use methods for tackling this.

Remedies run the gamut from the traditional 18th century methods still in use; to insecticidal soaps, botanicals, fungicides and other compounds as well as chemicals fresh from the latest laboratory discoveries.

There is a variety of hydroponic methods to choose from these include an all-water system, trays that hold roots and solutions are fitted with supports from which strings can hold an upright plant and working with rockwool, perlite and other highly useful hydroponic media which some gardeners enjoy.

Gardeners who incorporate all the above in a convenient greenhouse find that they are able to control the light, air, water and other factors much more easily than in other settings. Many greenhouses today are modular and these can be expanded as the garden ‘grows’.

It is helpful to have some knowledge of elementary botany before you start your garden. Plants have unique needs and hydroponics builds on that base. Knowing what factors are needed for flourishing plants is a good first step. Hydroponic gardening is great fun so why not get yours started today.