Propagation Media for plants
The plant propagating media is defined as “any agency that enables and helps the seed or any plant part kept in it, in getting good germination or rooting”.
Characteristics of a good Propagation Media
- The medium must be sufficiently firm and dense to hold the seed or cuttings in place during germination or rooting.
- Its volume must be fairly constant when either wet or dry. Excessive shrinkage after drying is undesirable.
- It must have a good water holding capacity so that watering does not have to be too frequently.
- It must be sufficiently porous so that excess water drains away permitting adequate aeration.
- It must be relatively free from weed seeds, nematodes and noxious (harmful) disease causing organisins.
- Its PH must be suitable for the plant being propagated or grown.
- It must be free from excess salts.
- It should withstand steam sterilization without any deleterious effects.
- It should not undergo any chemical change during sterilization or afterwards.
Types of Propagation Media
There are over ten different media and their chemical composition are as below:
1-Soil and its composition
Soil is composed of materials in solid, liquid and gaseous state in proper proportions for a satisfactory plant growth. The texture of soil refers to the relatuve proportion of:
- Sand (2 to 0.05 mm in particle diameter)
- Silt (0.05 to 0.002 mm -do-
- Clay (less than 0.002 mm -do-
The principal textural classes are: Sand, sandy loam, silt loam, clay loam and clay. A typical sandy loam may consist of 75% sand, 14% silt and 11% clay. Soil structure refers to the arrangement of the above particles in the entire soil mass.
2-Sand and its composition
Sand consists of all rock grains (of size ranging from 0.05 to 0.20 mm diameter) formed as a result of weathering of various rocks. Its mineral composition depends on the type of the parent rock. Quartz sand, generally used for propagation purposes, consists chiefly of a sillica complex. The type of sand used in plastering is satisfactory for rooting of cuttings. It is worthwhile mentioning that:
- Sand is the most widely accepted rooting medum for cuttings (particularly for ever green species)
- Relatively inexpensive and readily available.
- It is not as retentive of moisture as other media, Hence, needs frequent watering.
- It should be fine enough to retain some moisture around the cuttings, yet course enough to allow water to drain off.
3-Peat and its composition
Peat consists of the remains of aquatic, marsh, bog or swamp vegetation, which has been preserved under water in a partially decomposed state. Peat is often added to sand in varying proportions, mainly to increase the water holding capacity of the mixture. The combination makes an excellent rooting medium for cuttings of most species.
4-Sphagnum moss and its composition
Commerciaphagnum moss is the dehydrated remains of such acid be piants as Sphagnum papillosum and S. palustre. It is relately sterile, light in weight, has a very high water holdi, capacity (absorbs 10-20) times its weight of water). Stem and leaf tissues of sphagnum moss const largely of groups of water holding cells. It is generally shreed before it is used as a propagating medium. It containsvery small amount of minerals. It is also used with sand inqual parts for rooting stem, leaf and root cuttings.
The moss material that is used under our corlitions as a propagating medium is an epiphytic bryophyte hich grows abundantly on the tree trunks and branches in ne tropical and sub-tropical rain forests. As it possesses simar charac- teristics as sphagnum moss and since sphagnumnoss is not available in large quantities in our country, th epiphytic bryophyte is used in place of sphagnum moss.
5-Vermiculite and its composition
Vermiculite is amicaceous mineral which expands markedly when heated. Chemically, it is a hydrated magnesium-aluminium-iron silicae. It is very light in weight, neutral in reaction, insoluble in water and able to absorb and retain large quantities of water.
6-Leaf mold and its composition:
Maple, oak ani pongemia are among the leaf types suitable for leaf mold. In preparing such a medium alternate layers of leaves and soilare heaped up preferably under the shade. Watering once in a day will has ten the decomposition of the leaves. The leaf nold will be ready for use in about 10-11 months. It may contain nematodes, weed seeds and noxious insects and diseasses, so it should be sterilized before using.
7-Shreded bark, sawdust, wood shavings
It Can be used in soil mixes, serving much the same purpose as peat moss.
8- Potting mixtures
(i) For potting of rooted cuttings and young seedlings: 1 or 2 parts sand plus 1 part loamy soil plus 1 part peat moss or leaf mold.
(ii) For general container grown nursery stock: 1 part sand plus 2 parts loam soil plus 1 part peat moss or leaf mold plus 1/2 part well rotten F.Y.M.