Methods of vegetative propagation- Cutting and layering techniques
Article by:- Hemanth.S
Introduction:-
Several methods of vegetative propagation have been standardized for different horticultural crops. However, one method of propagation may be suitable for a particular crop but may not be suitable for the others. Similarly, one crop may be propagated on large scale with different methods of propagation, whereas, the others may have only one method.
Further, the success of different propagation methods is influenced by the environmental conditions. Hence, one method for a particular crop may be highly successful in a particular locality, but cannot be of any value in the other.
Types of cuttings
On the basis of plant part used and relative positions on a plant, cuttings are classified in various groups.
1. Stem cuttings:
A stem cutting is any cutting taken from the main shoot of a plant or any side shoot growing from the same plant or stem.
The shoots with high carbohydrate content usually root better. Broadly, there are four types of stem cuttings, namely hardwood, softwood, semi-hardwood and herbaceous cuttings.
2.Hardwood cuttings:
Cutting from mature and lignified stem of shrubs and trees are called as hardwood cuttings.
Hardwood cuttings are prepared during dormant season, usually from one-year-old shoots of previous season’s growth. The size of cuttings varies from 10 to 45 cm in length and 0.5 to 2.5 cm in diameter, depending upon the species.
Each cutting should have at least three or more buds.
For tropical and subtropical crops, straight cut is given at top in order to minimize transpiration loss and slant cut should be given at the base to expose more area for absorption of water and nutrients.
This helps in maintaining the polarity of the shoot and if rain occurs, water does not accumulate on the tip of the cutting, which saves the cutting from fungal infection.
3.Semi-hardwood (green wood) cuttings:
Semi-hard wood cuttings are those made from woody, broad-leaved evergreen species with partially matured wood.
These types of cuttings are mostly used in evergreen fruit plants like mango, guava, lemon, jackfruit some shrubs and shrubby ornamental plants.
The length of the cuttings varies from 7 to 20 cm.
It is necessary that leafy cuttings should be rooted under conditions when water loss from the leaves is minimum.
Commercially, such cuttings are rooted under intermittent mist, fog or under polyethylene sheets laid over the cuttings.
4.Softwood cuttings:
Cuttings prepared from the soft-succulent and non-lignified shoots, which are not hard or woody, are called as softwood cuttings.
Such types of cuttings are very prone to desiccation.
Usually the size of cutting is 5-5.7 cm but it may vary from species-to-species.
The best time for preparing softwood cuttings is late summer.
Softwood cuttings generally root easier and quicker than other types, but require more attention and sophisticated equipments.
Similarly, the temperature should be maintained 23 to 27oC during rooting at the base of cuttings.
5.Herbaceous cuttings:
Herbaceous cuttings are made from succulent non-woody plants like geranium, chrysanthemum, coleus, carnation and many foliage crops.
These are usually 7-15 cm long with few leaves retained at the upper end.
In such cases, basal ends of cuttings should be allowed to dry for few hours before planting.
Generally, fruit plants are not propagated by herbaceous cuttings.
Layering techniques
Layering is a form of rooting of cuttings in which adventitious roots are initiated on a stem while it is still attached to the plant. The rooted stem (layer) is then detached, transplanted, while later becomes a separate plant on its own roots. p
Tyes of layering:
1.Simple Layering
Simple layer consists of bending an intact shoot to the ground to cause adventitious roots to form.
This method can be used to propagate a wide range of plants, indoor or outdoor on woody shrubs that produce numerous suckers.
Layering is usually done in the early spring using flexible, dormant, one-year-old shoot-branches of the plant that can be bent easily to the ground.
These shoots are bent and “pegged down” at a location 15 to 20 cm from the tip forming a “U”shape.
2.Compound / serpentine layering
It is a modification of simple layering in which one-year-old branch is alternatively covered and exposed along its length.
The stem is girdled at different points in the underground part.
However, the exposed portion of the stem should have at least one bud to develop a new shoot.
Muscadine grape is commercially propagated by this method.
3.Continuous/trench layering
It is the most common method of propagation for woody plants, which produce long vines and are difficult-to-propagate by other methods of propagation.
Vigorous rootstocks of apple like M-16, and M-25 and walnut can easily be propagated by trench layering.
In this method, it is important to establish a permanent row of plants to be propagated.
4.Air layering ( Marcottage, Gootee, Pot layerage)
Air layers are made in the spring or summer on stems of the previous season’s growth.
The presence of active leaves on the layered shoot speeds root formation.
Layers are prepared by making an upward cut about 5 cm long at or about the centre of the shoot.
The shoot is then girdled by removing a ring of bark about 2 cm wide.
The upper part of wound is applied with IBA paste made in lanolin.
The wound is covered with moist sphagnum moss in a way to provide complete cover to it.
Polyethylene film is wrapped around the moss grass in such a way as to leave no opening, which could allow evaporation of moisture from the moss .
5.Mound /Stool layering /stooling
It is a method of propagation in which the shoots/plants are cut back to the ground and soil or rooting medium is mounded around new sprouts/shoots to stimulate roots to develop at their bases.
This method is commercially used to propagate apple, pear, quince, currants, gooseberry and other fruit crops.
In stooling, the mother plant is headed back to 15 to 20 cm above ground level during dormant season.
The roots in shoots may emerge within 30 to 40 days.
6.Tip layering
The tips of shoots are buried 5 to 10cm deep in the soil .
Rooting in buried shoots takes place within a month.
The new plants (layers) may be detached and transplanted in the soil during spring.
It is a natural method of propagation for black berries, raspberries etc.
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