Ugrow Organic: Propagation

One of the joys of hydroponics is growing on seeds and cuttings. Propagation is a very rewarding process. There are 3 basic methods of propagation.

• Seed Germination
• Rooting Stem Cuttings (a.k.a. cloning)
• Tissue Culture

Seed Germination

Seed germination refers to the sprouting of a seed in the first stages of a plants life. Seed germination is also known as sexual propagation. This method of propagation is popular as seeds are readily available, are usually of low cost, there is a wide variety to choose from and they are disease free plants to start with.

However the grower must be aware of the pitfalls that may occur when germinating seeds. They often give unpredictable and inconsistent results, their slow germination can delay the crop and male and female plants mixed together can lead to unwanted seed production with some species.

A standard method is to spread seeds evenly over a medium of loose or granulated Rockwool placed in a standard starting tray. The seeds are then covered with a thin layer of Rockwool or Perlite and the tray is covered to prevent moisture loss. The loose Rockwool makes it easy to thin, separate, and transplant seedlings. A variation on this method is the use of Rockwool 'cubes'. the Rockwool SBS system is particularly popular. A flat of cubes is placed in a standard starting tray. Each cube is in it own 'compartment' separated from one another. The cubes are soaked in lukewarm water or a weak and slightly acidic nutrient solution, and a seed is put into the 1/4" hole in the centre of each cube. The seeds are then covered with a thin layer of Perlite or vermiculite and the lid is placed on the tray. Once the seeds have sprouted, the cubes are easily broken off and placed into larger growing cubes or other aggregate.

Generally, until the first leaf is sprout, 24 hours light should be given. Once the first leaf is sprout the humidity tent on the starting tray should be removed daily to allow for aeration. The temperature should be between 75 F and 85 F. When the seed has fully sprouted the humidity tent should be removed and the lighting reduced to 18 hours a day. Nutrient solution should be diluted if used on the seedlings. Fluorescent lighting is suitable for seedlings. Once the seeds have sprouted, the cubes are easily broken off and placed into larger growing cubes or other mediums.

Stem cuttings

The stem cuttings method of propagation is formally known as 'cloning' or asexual propagation. Stem cuttings are taken from a healthy 'mother' plant and can be rooted within one to two weeks, producing a genetically identical clone of the mother plant. There is a significant time advantage with this method compared to seed propagation. Cloned plants mature much earlier than those started from seed. They also produce shorter and bushier plants of benefit to the commercial grower as growing space is gained for more plants in their nurseries. The most efficient way to 'root' the cutting is through a hydroponics system and many methods incorporate extra aeration and moisture to aid this process.

A cutting from the mother plant should be taken using a clean, sharp blade. A small branch which has a growing tip on with one or two leaves is ideal and there should be 2 to 4 inches of stem on the cutting. Make an additional cut on each stem just above the first cut and let them stand in water until you have as many as you require. Dip the stem in a root compound and place into a rooting cube. A popular method to root the cuttings is through the use of one inch Rockwool cubes which have been pH balanced, soaked in a diluted, high phosphorus nutrient solution and then placed in a standard propagation tray.

The tray should be covered with a clear dome to increase humidity and the plant exposed to 18 hours of diffused light a day. Lifting the cover a few times a day helps to prevent stale air building up. The cuttings should also be misted periodically with a mild foliar feed like kelp extract. Once the cuttings have rooted (determined by giving them a gentle tug), transplant them into the hydroponics system you have chosen for rearing.

Tissue Culture

Tissue culture is an advanced form of cloning by cell division and is beyond the focus of this article. For further information on tissue culture we recommended reading this Wikipedia article.