SGS Growing Guide - Fundamental Hydroponics

PLANT PROPAGATION FOR HYDROPONICS

Propagation
Propagation from seeds
Recommended seed varieties
Seed care
Propagation media
Propagating in rockwool
Root development
Transplanting seedlings
Transplanting to rockwool slabs
Cuttings
Cloning Process
Summary

Hydroponic gardening is the way of the future for environmentally controlled agriculture. By eliminating soil borne pests and diseases, while maximizing nutrient intake by the plant, phenominal yields can be achieved in a relatively small space.

PROPAGATION

Hydroponic gardening starts at the propagation stage. As with conventional gardening, the most popular propagation methods are from seeds or cuttings.

Most vegetable crops are started from seeds, the best varieties being "greenhouse" style vegetables. Herbs can also be started from seeds, but cuttings are often taken from a parent plant to start the next generation. Cuttings can be taken from plants grown from other cuttings for many subsequent generations.

Tissue culture is another propagation method gaining in popularity. Small tissue samples are taken from the parent plant, usually from bud cells. The cells are then grown in petri dish cultures. In this way, exact genetic duplication is possible, replicating hundreds of identical plants from a very small amount of plant tissue.

Although tissue culture propagation holds great promise for the future, conventional propagation methods are still the most widely used today.

PROPAGATION FROM SEEDS

Most vegetable crops are started from seeds, through the process of sexual reproduction. The seed is usually formed from two parents and contains part of the genetic code from each to produce a unique plant.

Inside the seed is an embryonic plant with its own food supply. Most vegetables are dicotyledons, in other words the seed contains two embryonic leaves. When environmental conditions are right, such as proper moisture levels, light, oxygen and temperature, the seed germinates. The seed sends down a root, then it divides to permit its two leaves to grow. Although each seed plant is a unique individual, plants of the same variety will have similar characteristics.

Commercial growers carefully select seed varieties with specific characterists in mind. Although practically any kind of commercial seed can be germinated and grown hydroponically, some varieties have characteristics ideal for "greenhouse" production.

RECOMMENDED SEED VARIETIES

For example, some tomato varieties recommended for hydroponic applications include:

Tropic
Dombito
Caruso
Larma
Perfecto
and Laura

Cucumber varieties include:

Toska 70
Pandex
Farbio
Sandra
Marillo
and Fidelio.

Recommend green to red bell peppers include:

Delphin
Plutona
Tango,
while Luteus and Goldstar are good green to yellow peppers.

European lettuce varieties recommended for hydroponic growing include:

Deci-Minor
Ostinata
Satonia
and Buttercrunch

And good looseleaf varieties include:

Domineer
Grand Rapids
Black-Seeded Simpson
and Waldmann's Dark Green.

SEED CARE

Seeds should be stored carefully. A seed is a living thing. It respires, using energy, even in its dormant state. Store plants in a cool dry place to help insure high germination rates.

If seeds were improperly stored and have only a marginal ability to germinate, a seed coat may be applied to help the plant get off to a good start. Seed coats contain nutrients and vitamins to supplement initial growth. Seed coats also protect the seeds. Graphite and polyacrylamite crystals in the seed coat can hold up to 200 times their weight in water, congeling into an excellent protective coating for the seed when exposed to moisture.

PROPAGATION MEDIA

There are several good propagation media used in hydroponics.

Peat plugs are popular for starting seeds. Condensed peat is held in a nylon net. Two or three seeds are sown directly into each plug. When water is added, the plug swells to many times its original size. Peat plugs are nutrient rich, so no fertilizers need to be added to the medium for one or two weeks. Once the seedlings appear, cut off the weaker plants so only the strongest plant remains in each plug.

Perlite/Vermiculite is another popular propagation medium. Course perlite provides good aeration and drainage, while vermiculite provides good water and nutrient holding capacity. Sow the seeds directly into the mixture, then cover the top with a layer of finely ground perlite. The surface perlite tends to dry out well, reducing the chance of fungus growth and disease.

Rockwool is the most popular propagation medium. Rockwool has high air and water holding capacity, and comes in many shapes and sizes. A sheet of one inch propagation cubes fits perfectly in an 11" by 22" nursery flat, and can hold up to 98 plants.

PROPAGATING IN ROCKWOOL

Here's how rockwool propagation is done.

The rockwool sheet is first placed in its tray. Rockwool conditioner is then added. Since rockwool is naturally alkaline, the sheet must be completely submerged in the conditioning solution for 24 hours to bring the pH down to acceptable levels. The conditioner also provides B vitamins and nutrients helpful to the plants initial growth.

After 24 hours, drain out and discard the solution by picking up the flat and pouring off all of the excess water.

Seeds may be planted directly into the rockwool cubes. Once the seeds are planted, cover the tray with the huymidity dome. Since the system is closed, 90% relative humidity will be maintained under the dome.

A heating mat or heating cable may also be used. Simply set the tray on the heating mat, and an ideal substrate temperature will be maintained. Since the ideal temperature for germinating seeds is 75-80 degrees, the mat will warm the substrate without overheating the air.

Never allow the rockwool substrate to completely dry out. If necessary, reirrigate with a 1/2 strength nutrient solution. Don't use a full strength nutrient solution, since too high a concentration of mineral salts can stress the young plant. Use just enough solution to keep the substrate moist, pouring off any excess liquid.

Lighting is also important. Full spectrum fluorescent grow lights are recommended, but cool white flourescent lamps may be substituted if desired. The lights should be hung 2 to 4 inches above the plants, and left on 24 hours a day. Good lighting promotes rapid initial growth and helps strengthen the plant to fight disease.

ROOT DEVELOPMENT

There are several ways to promote strong root growth.

Root hormones come in powdered and liquid forms, but the active ingrediate in both is IBA, indolebutyric acid. Small quantities of IBA promote strong root growth, reduce stress and prevent disease.

Careful management of nutrients and lighting can also promote root development in the early stages. A nutrient solution with a high phosphorus content stimulates initial root growth, but after the roots are well established, it should be replaced with a high nitrogen solution to promote stem and leaf development. Lighting with a strong red spectrum also helps initial root growth, but it must be balanced with blue light at the growth stage to prevent plants from becoming tall and spindly.

TRANSPLANTING SEEDLINGS

Once the roots are well established, they are ready to be transplanted. Most plants are ready for transplanting after 10 to 14 days, but spinach and slow herbs could take 3 weeks or more.

If a rockwool propagation system is used, simply lift up the cube and examine the roots. If they are well established, the plant is ready to be transplanted. If another propagation medium is used and you can't see the roots, wait until you can see 2 sets of leaves. The first set are the embryonic leaves. The next set are the plant's first true leaves, which means that the roots are becoming established.

Seedlings can be transplanted from soil to a hydroponic medium. Gently break away the soil, being careful not to damage the root hairs. Then gently rinse the roots in warm water, preferably water in which a hormone/vitamin supplemented has been added. Then place the plant in the new hydroponic medium. The plant may show signs of stress or shock for the first 7 to 10 days, then it should be all right.

Transplanting from peat plugs or rockwool is easy. Simply place the plug in the new medium and cover to the top of the plug. The plug helps anchor the plant and provides a good foundation for the roots. In an "ebb and flow" system, the seedlings should be irrigated with a 1/2 strength nutrient solution. Set the timer to irrigate the seedling six to eight times a day.

In an aeroponic system, simply place the cube in the web pot. The roots will grow easily through the medium into the mist chamber.

Rockwool propagation cubes may also be transferred to bigger growing blocks. This gives the roots more time to get established in rockwool.

TRANSPLANTING TO ROCKWOOL SLABS

Once the roots are established in the growing blocks, the plants can be be transplanted to growing slabs.

Rockwool slabs are about 3 feet long and are enclosed in plastic. Before transplanting, soak the slab for 24 hours with rockwool conditioner to lower its pH. Then cut drainage slits in the sides of the plastic. Once the slab is drained, cut X's where the plants are to be placed. 3 or 4 plants can be spaced on each slab. When you are ready, simply set your plants in position, and secure the blocks to the slab with stakes. Once the feeder lines are in position, and the transplanting is complete.

During this stage, full spectrum lights should be used, preferably 12 to 18 hours a day. Ideally, the root substrate should be slightly warmer than the air temperature, a good target being a 74 degree root temperature with a 72 degree air temperature. Some young plants, however, such as tomatoes and peppers, thrive at temperatures as high as 80 degrees.

CUTTINGS

Another popular method of propagation is from cuttings, an assexual method of reproduction.

Since a plant grown from a cutting only has one parent, the new plant will be a genetic duplicate of the host. Therefore, cuttings can be taken to reproduce plants with specific qualities.

Furthermore, since a cutting already has some initial growth, it will be have a stronger stalk and reach maturity faster than a plant germinated from seed.

Since a cutting takes time to develop its own root system, it must be able to survive for some time on its own water and nutrients. Horticultural aids such as cloning gels improve the plant's chances tremendously.

A cloning gel contains:

macroelements, such as potasium and nitrogen
trace elements, such as boron and molybdenum
root hormones, such as IBA to stimulate root growth
antimicrobial agents, to fight toxic pathogens and reduce damping off effects
B vitamins, to reduce the effects of plant stress
fungicides, to fight diseases caused by high humidity
and a protective gel, to seal the wound and prevent embolism

Embolism is condition in which a bubble of air gets trapped in the stem, preventing moisture from flowing upward, eventually killing the plant.

CLONING PROCESS

The cloning process is quite simple. First the cutting instrument is sterilized in a mild chlorine solution or alcohol, and a suitable hydroponic medium is prepared. The initial cut is taken below a node, and the cutting is dipped immediately in warm water to which a few drops of vitamin/hormone supplement has been added. The final cut is taken under the water to prevent an embolism.

The bottom leaves are then removed, from which point the new roots will generate, and the cutting is inserted immediately in a cloning gel to seal the wound. Then the cutting is transferred immediately to the hydroponic medium.

Cloning wax can also be helpful. Cloning wax temporarily seals the leaf stomata, restricting the transpiration of water from the plant and promoting strong root growth. For example, in this aeroponic system a cutting dipped in cloning gel was added to a web pot and the leaves were sprayed with cloning wax. No humidity dome was used, yet the cutting retained its moisture and developed its own root structure very quickly.

No matter what hydroponic system you use, cloning gel and cloning wax make propagation from cuttings fast and easy.

SUMMARY

In conclusion, let's take a moment to summarize the general propagation techniques for hydroponics:

* vegetables are propagated mainly from seeds
* herbs are propagated mainly from cuttings
* seed coats help marginal seeds to germinate
* cloning gels help cuttings to develop
* humidity domes or cloning wax inhibit the transpiration process, giving the plant more time to develop strong roots.

* 1/2 strength nutrient formulas can be used, promoting growth.
* fluorescent lights can be used, 2 to 4 inches above the plant.
* grow lights with a full spectrum, including red, are most beneficial.
* temperature control, particularly at the substrate, is beneficial.

If these simple techniques are followed at the propagation stage, the grower will be off to an excellent start for a successful hydroponic garden!
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