Division

You have learnt about propagating plants asexually from cuttings in Plant propagation 2. Plant cuttings are just one technique used to produce more plants asexually. Division, budding, grafting and natural vegetative propagation are other techniques that can be used.

Modified plant parts

Many plants grow from modified roots or stems where food is stored in the modified plant part. Some perennial (long-lived) plants die back to a modified food store during their dormant season. The plant uses the stored food for new growth after dormancy.

Modified stems include:

• crowns
• stem  tubers
• runners
• stolons
• bulbs
• corms
• rhizomes.

Modified roots include:

• root tubers.

Crowns

The crown is the part of the plant below the soil surface from which new shoots grow.

A crown can be divided into smaller pieces using a garden fork, sharp spade or knife or by hand. The tool used depends on the size of the plant involved.

If the plant to be divided has a period of dormancy it should be divided just before regrowth. If the plant has leaves all year round then the plant should be divided in early spring. The leaves should be cut back by two thirds to prevent water loss and wilting while the new shoots are developing.

Examples of plants that grow from a crown are: flax, sedum and chrysanthemum.

Tubers

There are two types of tubers: stem tubers and root tubers.

Stem tubers

The stem tuber you are probably most familiar with is the potato.

A stem tuber:

• is a swollen underground stem
• can produce shoots from buds, also known as ‘eyes’
• can be divided by being cut into pieces or grown from a small tuber known as a  ‘seed’ tuber.

Once divided, each piece of stem tuber has a bud or eye that will grow to produce roots and shoots. The piece of stem tuber will provide the energy for growth until the new shoot is above ground level.

Dividing a stem tuber

You will need:

• a potato
• chopping board
• knife
• warm dark dry area
• newspaper
• plastic bag.

What to do

• Place the potato in a warm dark airy dry place until buds begin to develop. Check your potato daily.
• Once buds have begun to develop, divide your potato into pieces and make sure there is a bud or eye on each piece. Each piece should be about the size of an egg.
• Leave the cut pieces to dry overnight.
• Next day wrap the pieces in newspaper, place in a plastic bag and send them to your teacher with your workbook.

Your teacher will comment on how successful your division of a stem tuber has been.

Overseas students do not send plant material into New Zealand. Take a photo of your divided stem tuber showing the bud on each piece. Send the photo to your teacher.

Root tubers

Dahlias and kūmara are examples of root tubers.

A root tuber:

• is a swollen root
• can be divided in spring
• Each piece must have a piece of tuber with a bud.

Rhizomes

Some types of iris grow from underground stems called rhizomes.

Rhizomes:

• are stems that grow under the soil surface
• can be divided by cutting the parent plant into sections when the plant is dormant. Each section must have a bud at a node. New shoots and roots will form from the buds.

Canna lilies, irises, rhubarb, kikuyu, ginger and bamboo are propagated from rhizomes.

     

Use a sharp, clean spade or knife to divide the rhizome. A sharp, clean implement is less likely to transmit disease or damage plant tissue.

A clean cut will heal faster with less chance of disease entering the wound.

Plant the new plants at a normal depth in friable, fertile soil and keep watered.

If the rhizome isn’t dormant then cut any leaves back by two thirds. This will prevent water loss and wilting.

Plants that don’t have a dormant period can be divided in autumn. Dividing the plants in autumn gives the new plants time to establish before active growth in spring. They are less likely to suffer from a lack of water at this time of year.

Taller plants like bamboo may need a stake for support until the new plant roots are fully established.

More modified stems

Runners and stolons

Bulbs

Whenever you eat an onion you are eating the bulb of an onion plant. Examples of plants propagated by bulbs include plants from the onion and daffodil families.

Daffodil

     

Corms

Corms look like bulbs and are often confused with them. There are no modified leaves on a corm as in the onion. Corms are squashed, compressed stems. They can’t be pulled apart into individual leaf scales.

Corms:

• are flattened underground stems swollen with food
• produce cormlets at their bases.

Suckers

Offsets

What's next?

Go to: 2 Layering.