Lesson 1.5 Sexual and Asexual Propagation
Completion requirements
Section 1: Plant Breeding and Propagation
Lesson 5: Sexual and Asexual Propagation
Plant propagation methods can be classified into two major categories:
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Sexual propagation is producing new plants from plant seeds. The production of seeds includes the flower and fruit of a plant; therefore, the flower, fruit, and seeds are known as the sexual parts of a plant.
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The method of propagating plants from seeds is known as
sowing, seeding, or planting.
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The method of propagating plants from seeds is known as
sowing, seeding, or planting.
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Asexual propagation is producing new plants
from plant stems, leaves, or roots. These are the vegetative parts of a plant; therefore, asexual propagation is also known as
vegetative propagation.
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The methods of propagating plants from vegetative parts are cuttings, division, layering, and grafting.
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The methods of propagating plants from vegetative parts are cuttings, division, layering, and grafting.
Sowing, Seeding, or Planting
The three terms sowing, seeding, and planting are synonyms and they refer to using seeds to grow new plants.
As you learned in Unit 1, seeds are ripened fertilized eggs of flowering plants.
Each seed contains a tiny plant or embryo, which is stored in a seed coat along with stored-up food either in, or around, its seed leaves.
For a seed to germinate, it requires water, air, and the proper temperature.
The seed absorbs the water which enables certain enzymes in the seed to convert stored starches into sugars.
These sugars make the embryo grow and burst through the water-softened seed coat, and a seedling plant is started on its way.
©iStock
Cuttings
Cuttings
Cuttings are vegetative parts of plants, the roots, stems, or leaves that are cut from a parent plant and inserted into water, sand, peat moss, vermiculite, or perlite, where they form roots and become new plants.
Root cuttings are used to propagate many houseplants.
Stem cuttings are used for plants with woody stems, such as roses.
Leaf cuttings are often made from the leaves of certain plants that are succulent or fleshy, especially those from tropical regions.
As an example, the leaf of an African violet can be removed from the parent plant, and its stem trimmed to a length of about three centimetres. It is then stuck into a rooting medium so that the entire stem and a small portion of the bottom of the leaf is in contact with the growing medium and supported in an upright position. Baby plants will appear where the leaf contacts the rooting medium in about six to eight weeks, depending on the environmental conditions.
Root cuttings are used to propagate many houseplants.
Stem cuttings are used for plants with woody stems, such as roses.
Leaf cuttings are often made from the leaves of certain plants that are succulent or fleshy, especially those from tropical regions.
As an example, the leaf of an African violet can be removed from the parent plant, and its stem trimmed to a length of about three centimetres. It is then stuck into a rooting medium so that the entire stem and a small portion of the bottom of the leaf is in contact with the growing medium and supported in an upright position. Baby plants will appear where the leaf contacts the rooting medium in about six to eight weeks, depending on the environmental conditions.
A stem cutting. ©iStock
Division
Division is one of the easiest methods of propagation and consists of simply using a sharp spade to dig out a large clump of a plant and then replanting it immediately. Rhubarb is a good example of this method.
Alternatively, the division may consist of a part not yet rooted, such as tulip bulblets that take root readily after being removed from the parent plant. Other division methods incorporate stolons or slender branches, i. e. a strawberry "runner", which naturally take root after being cut apart from the parent.
Alternatively, the division may consist of a part not yet rooted, such as tulip bulblets that take root readily after being removed from the parent plant. Other division methods incorporate stolons or slender branches, i. e. a strawberry "runner", which naturally take root after being cut apart from the parent.
A clump of young rhubarb shoots can be dug out and
replanted in spring to produce a new plant.
Layering
Layering
Layering is accomplished by bending and covering branches with soil, except the tip, which must be kept uncovered. The soil-covered part of the branch can be held in place with pegs or stones until rooted. The branches are often scraped or cut
on the underside at the points where rooting is desired. This helps the quick formation of roots.
Layering is often used for vines, or other plants whose cuttings root poorly.
In all cases of layering, the parent plant supplies the food until the new plant has an adquate root system and can survive on its own.
Then the rooted branch can be cut from the parent plant and planted as a separate individual.
In all cases of layering, the parent plant supplies the food until the new plant has an adquate root system and can survive on its own.
Then the rooted branch can be cut from the parent plant and planted as a separate individual.
An illustration of layering.
Grafting
Grafting is the process whereby a part taken from one plant is united with and made to grow on another plant.
For example, a small branch of an apple tree can be sliced off and united with a sliced branch on another tree.
The uniting of the slices can be done by firmly tying them together so as to have tree sap flowing freely from one part to the other part. The binding must remain in place until the two parts have grown together.
An example of grafting. ©iStock
How do you determine the right propagation technique for a particular plant?
To help you with that, click here.
To help you with that, click here.