This page has been designed to help answer the important questions beginning
growers might have when just getting started in hydroponics. A lot of these
concepts are connected to each other. Follow the links and put the pieces of
this growing puzzle together.
The more you know, the easier it is to grow!
During photosynthesis, plants use carbon
dioxide (CO2), light, and hydrogen (usually water) to
produce carbohydrates, which is a source of food. Oxygen
is given off in this process as a by-product. Light is a key variable in
Measuring nutrient solution strength is a
relatively simple process. However, the electronic devices manufactured to
achieve this task are quite sophisticated and use the latest microprocessor
technology. To understand how these devices work, you have to know that pure water
doesn’t conduct electricity. But as salts are dissolved into the pure water,
electricity begins to be conducted. An electrical current will begin to flow
when live electrodes are placed into the solution. The more salts that are
dissolved, the stronger the salt solution and, correspondingly, the more
electrical current that will flow. This current flow is connected to special
electronic circuitry that allows the grower to determine the resultant
strength of the nutrient solution.
The scale used to measure nutrient strength is electrical conductivity (EC)
or conductivity factor (CF). The CF scale is most commonly used in
hydroponics. It spans from 0 to more than 100 CF units. The part of the scale
generally used by home hydroponic gardeners spans 0-100 CF units. The part of
the scale generally used by commercial or large-scale hydroponic growers is
from 2 to 4 CF. (strength for growing watercress and some fancy lettuce) to as
high as approximately 35 CF for fruits, berries, and ornamental trees. Higher
CF values are used by experienced commercial growers to obtain special plant
responses and for many of the modern hybrid crops, such as tomatoes and some
peppers. Most other plant types fall between these two figures and the
majority is grown at 13-25 CF.
When a seed first begins to grow, it is germinating. Seeds are germinated in
a growing medium, such as perlite. Several factors are
involved in this process. First, the seed must be active–and alive–and not in
dormancy. Most seeds have a specific temperature range that
must be achieved. Moisture and oxygen must be present.
And, for some seeds, specified levels of light or darkness must be met. Check
the specifications of seeds to see their germination requirements.
The first two leaves that sprout from a seed are called the seed leaves, or
cotyledons. These are not the true leaves of a plant. The seed develops these
first leaves to serve as a starting food source for the young, developing plant.
Soil is never used in hydroponic growing. Some systems have the ability to
support the growing plants, allowing the bare roots to have maximum exposure to
the nutrient solution. In other systems, the roots
are supported by a growing medium. Some types of media also aid in moisture and
nutrient retention. Different media are better suited to specific plants and
systems. It is best to research all of your options and to get some
recommendations for systems and media before making investing in or building an
operation. Popular growing media include:
There are a number of other materials that can (and are) used as growing
media. Hydroponic gardeners tend to be an innovative and experimental group.
The apparatuses used in hydroponic growing are many and varied. There are two
basic divisions between systems: media-based and water culture. Also, systems
can be either active or passive. Active systems use pumps and usually timers and
other electronic gadgets to run and monitor the operation. Passive systems may
also incorporate any number of gadgets. However, they to not use pumps and may
rely on the use of a wicking agent to draw nutrient to the roots.
Media-based systems–as their name implies–use some form of growing
medium. Some popular media-based systems include ebb-and-flow (also called
flood-and-drain), run-to-waste, drip-feed (or top-feed), and bottom-feed.
Water culture systems do not use media. Some popular water culture systems
are raft (also called floating and raceway), nutrient film technique (NFT), and
Think of a plant as a well-run factory that takes delivery of raw materials
and manufactures the most wondrous products. Just as a factory requires a
reliable energy source to turn the wheels of its machinery, plants need an
energy source in order to grow.
Usually, natural sunlight is used for this important job. However, during
the shorter and darker days of winter, many growers use artificial lights to
increase the intensity of light (for photosynthesis)
or to expand the daylight length. While the sun radiates the full spectrum
(wavelength or color of light) suitable for plant life, different types of
artificial lighting are selected for specific plant varieties and optimum
plant growth characteristics. Different groups of plants respond in physically
different ways to various wavelengths of radiation. Light plays an extremely
important role in the production of plant material. The lack of light is the
main inhibiting factor in plant growth. If you reduce the light by 10 percent,
you also reduce crop performance by 10 percent.
Light transmission should be your major consideration when purchasing a
growing structure for a protected crop. Glass is still the preferred material
for covering greenhouses because, unlike plastic films and sheeting, its light
transmission ability is indefinitely maintained.
No gardener can achieve good results without adequate light. If you intend
to grow indoors, avail yourself of some of the reading material that has been
published on this subject. If you are having trouble growing good plants, then
light is the first factor to question.
A large part of the success in growing hydroponically is planning where to
place the plants. Grow plants that have similar growing requirements in the
same system. Placing your system 1-2 feet away from a sunny window will give
the best results for most herbs and vegetables. Even your regular house lights
help the plants to grow. Make sure that all of the lights are out in your
growing area during the night. Plants need to rest a minimum of 4 hours every
night. If your plants start to get leggy (too tall and not very full), move
the system to a spot that has more sun. Once you find a good growing area,
stick to it. Plants get used to their home location. It may take some time to
get used to a new place.
–Charles E. Musgrove
Plants need around 16 mineral nutrients for optimal growth. However, not
all these nutrients are equally important for the plant. Three major
minerals–nitrogen (N), phosphorus (P), and potassium (K)–are used by plants
in large amounts. These three minerals are usually displayed as hyphenated
numbers, like “15-30-15,” on commercial fertilizers. These numbers
correspond to the relative percentage by weight of each of the major
nutrients–known as macronutrients–N, P, and K. Macronutrients are present in
large concentrations in plants. All nutrients combine in numerous ways to help
produce healthy plants. Usually, sulfur (S), calcium (Ca), and magnesium (Mg)
are also considered macronutrients.
These nutrients play many different roles in plants. Here are some of their
Boron (B), copper (Cu), cobalt (Co), iron (Fe) manganese (Mn), molybdenum
(Mo), and zinc (Zn) are only present in minute quantities in plants and are
known as micronutrients. Plants can usually acquire adequate amounts of these
elements from the soil, so most commercial fertilizers don’t contain all of
the micronutrients. Hydroponic growers, however, don’t have any soil to
provide nutrients for their plants. Therefore, nutrient
solution that is marketed for hydroponic gardening contain all the
In hydroponics, nutrient solution–sometimes just referred to as
“nutrient”–is used to feed plants instead of plain water. This is due
to the fact that the plants aren’t grown in soil. Traditionally, plants acquire
most of their nutrition from the soil. When growing hydroponically, you need to
add all of the nutrients a plant needs to water. Distilled water works best for
making nutrient. Hydroponic supply stores have a variety of nutrient mixes for
specific crops and growth cycles. Always store solutions out of direct sunlight
to prevent any algae growth. See also conductivity, macronutrients, and
Disposal Unlike regular water, you need to be careful where you
dispose of nutrient. Even organic nutrients and fertilizers can cause serious
imbalances in aquatic ecosystems. If you do not live near a stream, river, lake
or other water source, it is fine to use old nutrient on outdoor plants and
lawn. Another possibility is to use it on houseplants. However, if you live
within 1,000 feet of a viable water source, do not use your spent nutrient in
The ends of a plant’s roots aren’t open-ended like a drinking straw and
they definitely doesn’t suck up a drink of water or nutrients. Science is
still seeking a complete understanding of osmosis, so to attempt a full and
satisfactory description of all that’s involved in this process would be
impossible. However, we can understand the basic osmotic principle as it
relates to plants.
First, consider a piece of ordinary blotting paper, such as the commonly
used filter for home coffee machines. The paper might appear to be solid.
However, if you apply water to one side of it, you’ll soon see signs of the
water appearing on the opposite side. The walls of a feeding root act in much
the same way. If you pour water onto the top of the filter paper, gravity
allows the water to eventually drip through to the bottom side. Add the
process of osmosis and water that’s applied to the bottom side drips through
to the top.
With plants, this action allows water and nutrients to pass through the
root walls from the top, sides, and bottom. Osmosis is the natural energy
force that moves elemental ions through what appears to be solid material. A
simplistic explanation for how osmosis works, although not 100 percent
accurate, is that the stronger ion attracts the weaker through a semipermeable
material. So, the elements within the cells that make up plant roots attract
water and nutrients through the root walls when these compounds are stronger
than the water and nutrients applied to the outside of the roots.
It then follows that if you apply a strong nutrient to the plant roots–one
that’s stronger than the compounds inside of the root–that the reverse
action is likely to occur! This process is called reverse osmosis. Many
gardeners have at some time committed the sin of killing their plants by
applying too strong a fertilizer to their plants, which causes reverse
osmosis. Instead of feeding the plant, they have actually been dragging the
life force out of it.
Understanding how osmosis works, the successful grower can wisely use this
knowledge to promote maximum uptake of nutrients into the plants without
causing plant stress–or worse, plant death–from over fertilizing. All plants
have a different osmotic requirement or an optimum nutrient strength.
As a result of the process of photosynthesis,
oxygen (O) is given off by plants. Then, at night, when light isn’t available
for photosynthesis, this process is reversed. At night, plants take in oxygen
and consume the energy they have stored during the day.
Even though hydroponic gardeners dodge a large number of plant problems by
eschewing soil (which is a home to any number of plant enemies), pests and
diseases still manage to wreak havoc from time to time. Botrytis, Cladosporium,
Fusarium, and Verticillium cover most of the genera of bacteria that can
threaten your plants. The insects that can prove annoying include aphids,
caterpillars, cutworms, fungus gnats, leaf miners, nematodes, spider mites,
thrips, and whiteflies.
A few good ways to prevent infestation and infection are to:
With insects, sometimes you can pick off and crush any large ones. Or you can
try to wash the infected plants with water or a mild soap solution (such as
If a problem gets out of control, it may be necessary to apply a biological
control in the form of a spray. Research which product will work best in your
situation. Always follow the instructions on pesticides very closely.
Alternatively, there are a number of control products on the market today
that feature a botanical compound or an ingredient that has been synthesized
from a plant material.
On botanical compounds as controlling agents:
Over the last few years, researchers from all around the world have started
to take a much closer look at any compounds present in the plant kingdom that
might hold the answer to our pest and disease control problems. Many companies
have even switched from producing synthetic pesticides to copying nature by
synthesizing naturally occurring compounds in a laboratory setting. Extracts
of willow, cinnamon, grapefruit, garlic, neem, bittersweet, lemon grass,
derris, eucalyptus, and tomato have been helpful in controlling diseases and
–Dr. Lynette Morgan
The pH of a nutrient solution is a measurement
of its relative concentration of positive hydrogen ions. Negative hydroxyl
ions are produced by the way systems filter and mix air into the nutrient
solution feeding plants. Plants feed by an exchange of ions. As ions are
removed from the nutrient solution, pH rises. Therefore, the more ions that
are taken up by the plants, the greater the growth. A solution with a pH value
of 7.0 contains relatively equal concentrations of hydrogen ions and hydroxyl
ions. When the pH is below 7.0, there are more hydrogen ions than hydroxyl
ion. Such a solution “acidic.” When the pH is above 7.0, there are
fewer hydrogen ions than hydroxyl ions. This means that the solution is
Test the pH level of your nutrient with a kit consisting of vials and
liquid reagents. These kits are available at local chemistry, hydroponic,
nursery, garden supplier, or swimming pool supply stores. It is also a good
idea to test the pH level of your water before adding any nutrients. If your
solution is too alkaline add some acid. Although such conditions rarely occur,
sometimes you may have to reduce the level of acidity by making the solution
more alkaline. This can be achieved by adding potassium hydroxide (or potash)
to the solution in small amounts until it is balanced once again.
–Charles E. Musgrove
Plants need to absorb many necessary nutrients from the nutrient solution
or–in the case of traditional agriculture–the soil. However, plants can create
some of their own food. Plants use the process of photosynthesis to create food
for energy. Carbohydrates are produced from carbon dioxide (CO2) and a source of
hydrogen (H)–such as water–in chlorophyll-containing plant cells when they are
exposed to light. This process results in the production of oxygen (O).
Every now and again, you are sure to run into a problem with your plants.
This is just a simple fact of any type of gardening. The key is to act quickly,
armed with quality knowledge.
Nitrogen deficiency will cause yellowing of the leaves, especially in the
older leaves. The growth of new roots and shoots is stunted. In tomatoes, the
stems may take on a purple hue.
A phosphorous deficiency is usually associated with dark green foliage and
stunted growth. As in nitrogen deficiency, the stems may appear purple. But
since the leaves don’t yellow as they do in nitrogen deficiency, the whole
plant can take on a purplish green color.
Iron deficiency results in yellowing between the leaf veins. In contrast to
nitrogen deficiency, the yellowing first appears in the younger leaves. After
a prolonged absence of iron, the leaves can turn completely white.
This condition can be caused by environmental factors or disease (usually
caused by Fusarium). Nutrient and media temperature can be adjusted to remedy
wilt. However, if Fusarium have taken hold, the chances that your plants will
survive are slim.
If wilting is due to environmental causes:
Try to spray the plants and roots with cool, clean water to rejuvenate
them. If this hasn’t helped them by the next day, try it again. If the
plants respond, top-off the nutrient solution and check the pH. If the plants
don’t respond to the misting, empty the tank, move it to a shadier spot, and
refill with cool, fresh nutrient solution. Don’t reuse the old
solution–start with fresh water and nutrients.
–Charles E. Musgrove
If wilting is due to a system blockage of nutrient:
I have seen tomato plants that have been so dehydrated due to a nutrient
supply blockage that they were lying flat and for all the world looked
stone-cold dead. When the nutrient flow resumed and the plants were given the
less stressful environment of nighttime, they rebounded so well that I
wondered if I had dreamed the previous day’s “disaster.” The moral
of this story is to always give plants a chance to revive, even when the
situation looks hopeless.
Plants can be propagated by a number of methods. Growers can let a plant go
to seed, collect the seeds, and then start the cycle over again (see germination).
Another method is to take stem cuttings, which is also known as cloning (because
you are creating an exact copy of the parent plant).
Although this process won’t work with all plants, it is a highly effective
technique. Simply cut off a side shoot or the top of the main shoot just below a
growth node. Make sure that there are at least two growth nodes above the cut.
Remove any of the lower leaves near the base of the new plant. This cutting can
then be rooted by placing it in water or in a propagation medium (perlite works
well) that is kept moist. The use of some rooting hormone can help your chances
Remove any discolored, insect-eaten, or otherwise sick-looking leaves from
plants. Picking off some outer leaves or cutting the top off a plant can help it
grow fuller. Use sharp scissors to prune your plants. Sometimes you will want to
prune a plant to focus its energy on the remaining shoots. Pruning is an art and
should be performed with care. Damaged or dying roots may also need to be pruned
from time to time.
Never use soil during any aspect of hydroponics. If you ever move a plant
from a soil-based situation to hydroponics, remove all traces of soil or
potting mix from the roots. Soil holds lots of microbes and other organisms
and materials that love to grow in and contaminate your hydroponic system.
Some of these will actually parasitize your plant and slow its growth. This is
another advantage of hydroponic growing: The plant can get on with growing
without having to support a myriad of other organisms as happens in
conventional soil growing.
Different plants have different germination and
growing temperatures. Always make sure that you check each plant’s growing
requirements–especially minimum and maximum temperature levels. Keep in mind
that specific varieties of plants may have different requirements.
Because the water supply is the source of life for your plants, quality is
important. All plants rely on their ability to uptake water freely. Between 80
and 98 percent of this uptake is required for transpiration (loosely compared
to perspiration in animals), which allows the plant to produce and somewhat
control its immediate microclimate. Plants also need clean, uncontaminated
water to produce their own healthy food supply.
The water you use in your hydroponic system needs to be pure. It is always a
good idea to test your water source before adding nutrients so you aren’t adding
an element that is already present. In small systems, it would be wise to use
If you are starting a larger hydroponic operation, it would be a good idea to
have a water analysis completed. Factors such as sodium chloride (NaCl, or salt)
content and hardness will be of great use to growers. Also, groundwater can have
elements normally not present in conditioned water. A key piece of advice: Get
to know your water!
Rooting a Cutting:
- have everything ready first then take your cuttings and plant them right
- for best results, take cuttings first thing in the morning
- use only healthy actively growing stock plants with soft green stems
(woody stem cuttings do not root fast!!!)
- for green stem (softwood) cuttings use a straight clean cut; for yellow or
brown stem cuttings use a slanted cut
- remove any leaves or branches that would be below the soil line (snip off
leaf stem, leaving a 1/4″ stub)
- dip cutting into “Roots” or other hormone products
- after planting, trickle a few drop of water down the stem to settle the
soil mix around the stem
To Root in Potting Soil or Soiless Mixes:
- fill containers with potting mix
- water well with room temperature water with “Nutri-Boost” added
(“Nutri-Boost” is a vitamin mix; add 7 drops per litre or quart of
- it is always a good idea to have “No-Damp” nearby in case you
notice any signs of wilting; if this occurs, use the recommended application
rate of l0m. “No-Damp” to 1 litre of water and spray generously
- now take your cuttings, dip them into a rooting hormone and plant them
To Root in Rockwool Cubes:
- rinse cubes in lukewarm pH balanced water
- water cubes with “Nutri-Boost” solution as described above
- plant the cutting 3/4″ of the way into the cube
More Helpful Hints:
- root cuttings under moderate light (flourescent light)
at 70 – 75°F
- if you use a clear cover, remove twice a day and wipe any condensation off
the cover and replace
- use only water and “Nutri-boost” solution until cuttings show
signs of new growth at tips then feed with 1/2 strength fertilizer
Hydroponic Nutrient Manipulation and Modification Techniques
or “Playing with your food”
Some gardeners are ignoring their mother’s advice and modifying their
fertilizer mixes. The fact is, the soil-less mixes, lava rock, rockwool, etc.
hold little or no food compared to garden dirt, so any change in fertilizer
strength or quality is noticed by the plant almost immediately.
This is why gardeners use different fertilizers for different stages of
growth, giving the plant just what it needs for today’s “Work”. Here
are some other tips on changing your fertilizer mix for special circumstances.
We match food strength to growing conditions in the garden, and to the health
and activity of the plant.
Weak fertilizer for:
- newly rooted cuttings
- plants in low light conditions
- plants in hot gardens (over 90°F or 33°C)
- plants under stress – disease, bugs, etc.
- plants in transition between stages of growth
- plants in poor growing conditions – crowded, root-bound, poor air
Regular Strength Fertilizer for:
- healthy plants in active growth
- good light levels, temperature and air movement
Strong Fertilizers for:
- natural spurts of growth in crop plants
- plants in very good growing conditions – very high light levels; precise,
consistent temperatures; major air movement through plants; excellent
exhaust and intake fans; huge quantities of C02 delivered efficiently to the
garden; regular growth hormone treatments (to help the plant take up
Note: Increase food strength gradually – watch for black leaf tips!
Food Formulas – We modify fertilizers by changing the quantity of
individual nutrients for special circumstances.
Low Nitrogen Fertilizers:
- to avoid “stretching” (long thin stems) of plants between stages
- a good example would be a chrysanthemum grower who has shortened the day
length to make the plants start their flower cycle; he would use a full
strength fertilizer with Nitrogen only (1/2 strength or less) to keep the
plants compact until the flower buds form.
- return to regular Nitrogen levels once your plants have actually begun
their next growth stage.
- this trick works especially well with our “B” and “C”
You can see that gardeners start by examining the conditions in the garden
and the “job” of their plant, then decide what strength and quality to
mix their fertilizers.
So What’s the Deal with Pesticides?
Well, they suck! However, sometimes they are necessary to save your valuable
crop. The “new” trend is to use pesticides only as a last resort. Your
object is to control your pests and you might even get lucky and wipe them out.
Start with a healthy plant! It’s much less likely to develop problems than a
plant under stress. Bugs seem to sense a hurting plant, much like a pack of
wolves will prey on an injured or tired animal. That’s where our Predators come
In. Just wonderful little things. They are moderately priced and they do all the
work for you. When the bad guys are all gone, (ie. no more food), they either
pack their bags and leave, or eat each other down to the last one. Predators are
carnivores (eat meat) not herbivores (vegetarians), therefore no worries about
damage from them.
Predators have been used since before the “Dead Sea” was even sick.
It’s only since First World War France, where pesticides and rodenticides were
first used in the trenches to relieve troops of overwhelming infestations that
we have changed our thinking. We’ve been poisoning our land, our water, and
ourselves ever since. Some treatments are much safer than others. Pokon and
Safers Soap are a good organic way to go, plus we can get you Predators within a
day or two. This old/new topic is called “Integrated Pest Management”,
or I.P.M. for short.
Avoiding Plant Diseases
Watching healthy plants get sick and die is a very depressing sight to a
gardener. Plant diseases are always out there, waiting to attack your garden.
While sonic diseases are easily treated, other more serious diseases will
require repeat treatments to handle. Some diseases are so serious (tobacco
mosaic virus for example), that the plant is doomed. Plant diseases can
seriously lower crop production, even if the sick plants recover. Lets keep
diseases out of our gardens! Here’s how:
Good Growing Conditions and Practices:
The best defence against plant disease is to keep your plants healthy and
actively growing, by creating good conditions in your garden.
Attention to temperature, air movement and air change, proper spacing of
plants, consistent growing conditions – all these practices ensure healthy,
stress-free plants that can resist bugs and disease well. Often, bugs and
disease will attack a weak plant in your garden and build up armies to invade
the rest of your healthy plants!
Use Healthy Plant Stock
- a cutting from a sick plant will carry on the disease in the new plant.
- some varieties of a plant will have greater natural resistance to disease
than their “weak sisters”; if possible, grow only varieties that
have known disease resistance.
Keep Tools, Hands and Clothing Clean
- diseases, pests and insect eggs can travel to new host plants
- during pruning, transplanting and handling; wash your hands after handling
diseased plants before you touch a healthy one
- clean tools and knives well after use
- keep garden clear of dead leaves
Sterilize Garden or other Grow Mediums
(a Medium is what your roots are growing in)
- this is especially important when using garden dirt from the backyard in a
container indoors or when using recycled rockwool or lava rock for new crops
- the soil-less potting mixes and new rockwool are considered clean already
– no further treatment is needed
Use R/O Water or Distilled
- if you are concerned about the possibility of disease in your water, there
are a couple of simple methods to treat water and kill disease before you
infect your garden:Chlorine Bleach (1/4 cup for 30 gallons)
- add to water and stir well
- add fertilizer to water after treating with bleach
- use air pump and air stone to drive off bleach and keep water bubbly
Hydrogen Peroxide (35%) (1 tablespoon for 10 gallons)
- this product is actually water with extra oxygen, and the active
oxygen will kill disease in the water
- add to water
- stir well, then add fertilizer
Note: Peroxide helps plants to take up food easier and quicker, so this
treatment has an extra benefit to the garden.
Watch your garden for problems and treat them promptly! You may eliminate the
disease entirely, before it gains a foothold in your garden.
Treating Fungus and Bacteria in Your Garden
Seedlings and Newly Rooted Cuttings
- treat with No-Damp or other mild fungicide
- be sure roots are already wet before root-drench treatment: No-Damp
contains alcohol that could damage dry roots or unrooted cuttings
- treat plants once a week until plants recover
Vigorous Plants – Green Growth (no flowers or crop on plant)
- spray top-growth well with Safers Garden Fungicide
- wet all leaves until liquid runs off leaves
” Caution ” – Do not spray plants with flowers or crop on them; you
will definitely burn your crop!
- treat your plants once a week – the best time to spray is late in the day,
so the plants can dry in the dark; avoid spraying in strong light.
Flowering or Crop Plants
- treat plants by hand-watering Benomyl fungicide into the roots
” Caution ” – Never spray a flowering plant with fungicide; it
could damage the flower or crop!
- water enough Benomyl solution into the roots to drench the entire root
- treat the plants when the roots are already wet from feeding or watering,
and when they won’t be watered again for at least a few hours
- treat once a week
Hints on Treating Plants for Disease
- avoid high temperature and strong fertilizers until plants recover
- disease can become tolerant of a fungicide if used many times; after you
have used one product three or four times in a row, switch to another
suitable product and attack the disease with a new weapon.
Safers Garden Fungicide is a sulphur based product only for spraying Green
Do not use Safers Garden Fungicide for crop plants!