Hydroponic growers propagate by direct seeding, cloning (tissue culture, cuttings), & using soil grown plants. A discussion follows.
Direct seeding can be used for vegetable propagation.
Media used for seed propagation are:
Peat plugs: Condensed sphagnum held together by a net.
Rockwool cubes: If seeds do not need light to sprout sow & cover the cube surface with rockwool strands. Cubes stay with the plant throughout its life.
Combination mixtures: Peat is too wet for seed growth so it is mixed with vermiculite for drainage. A mixture of 1 part each peat, vermiculite & perlite may also be used.
Baggie method: Place seeds in a moist paper towel, coffee filter, or peat, & put in a baggie. Place in a warm place & transplant when sprouting occurs.
Seed growing tips:
Light: Seeds germinate in light or dark depending on the seed. Ideally grow lights, hung 2-4" above plants are on 24 hours daily until true leaves (second set of leaves) are seen; then 18 hours daily.
Temperature: Usually 75-85F (20-25 C) depending on the seed. Bottom heat such as an incubator, heating mat, or heating cable may be used.
Nutrient: Seeds need no nutrient to sprout since they have nutrition in the seed coat. Use 1/2 strength nutrient once true leaves appear. In general flush every 2-3 hours. Increase nutrient strength if the leaves turn yellow & decrease it if they turn brown.
Transplanting: Seeds are transplanted once roots develop as is indicated by fully expanded true leaves, visible roots, or feeling stem resistance with gentle tugging.
Non germinating seeds may be due to:
Seeds need pre-treatment (scarification,
Old, improperly stored, or diseased seeds (discolored
shriveled, cracked, moldy seeds).
Seeds need a longer germination time.
Improper media, system, or sprouting technique.
Seed variety not ideal for hydroponic growing.
Mixing acid & alkaline seeds.
Seed coat has germination inhibitors that were not
removed (i.e. palm).
The media needed an additive (i.e., orchids & special
Moldy seedlings: Some seeds (i.e., forage) may need fungal treatment before sowing.
A black stem & wilting indicates damping off. Media should have good drainage; a sphagnum based media may prevent this.
Long thin seedlings: Due to poor light, high temperature, excess nutrient. If using fluorescent lights change to grow lights.
Tissue culture involves taking small plant parts (buds, nodes, leaf, or roots), & growing them in containers with an agar based nutrient. Sterile technique & specialized equipment are used, since contamination can cause other things will grow in the media.
Cutting propagation involves cutting part of a plant & rooting it. Media used for cuttings include perlite, peat plugs, & rockwool cubes. Aeroponic systems use no media but roots cuttings quickly.
Cutting propagation tips
Nutrient: Nutrient should be 1/2-1/3 concentration.
Light: 18 hours daily.
Temperature depends on the plant usually 72-74 F (22-23°C).
Wilting: Caused by bacteria or other contamination, or the roots being unable to keep up with the water lost from the leaves (transpiration). Wilting can damage leaves or kill the cutting. Tips to decrease wilting are:
Use a rooting hormone.
Remove large & bottom leaves.
Transplant late afternoon.
Decrease light intensity.
Use a humidity dome & mist leaves frequently.
Remove growing tips.
Decrease the nutrient concentration. If too strong the
plant tries to equalize the salt concentration inside
and outside the roots. The plant releases water from
its tissues to dilute nutrients surrounding the root;
thus causing wilting.
Consider using willow water, aspirin, or salicylic
Increase root oxygen with a pump or hydrogen peroxide.
The cutting was taken at the wrong time. Proper times should be looked up. Examples are softwood (spring), semi-hardwood (summer), hardwood (fall), leaf (early summer), & root (fall).
If a hardwood cutting does not root take a heel or mallet cutting. Mallet & heel cuttings are taken from a cutting with a cross section at the base. A heel cutting looks like an arrow; a triangle of wood is cut at the base. A mallet cutting, or upside down "T" cut, involves cutting the top of the T at the base of the cutting. Wounding (notching the cutting bottom) can be made before rooting hormone treatment.
A rotting root cutting indicates too much moisture.
STARTING SOIL GROWN PLANTS
Soil based seedlings or plants can be transplanted to a hydroponic medium. There is a risk of introducing pests and disease, however. To transplant, gently remove root soil & rinse with warm water. Soak 24 hours & place in the hydroponic medium or system. A hormone or vitamin supplement can be added to the water.
© 2004 Baci