Vegetative Reproduction

Plants can reproduce either sexually (through spores or seeds) or asexually (vegetatively). There is a geographic pattern to plant reproduction: in the temperate zones of the world, cold winters make it difficult for plants to reproduce vegetatively, while in the tropics vegetative reproduction is an option for both wild and cultivated plants. Many tropical cultivars, especially the traditional Hawaiian crops are propagated vegetatively. To understand plants in the tropics, it is important to understand sexual and asexual reproduction.

Sexual and Asexual Reproduction Compared


Asexual (Vegetative) Reproduction Sexual Reproduction
Propagation
New plants start from pieces of old plants. New plants start from spores or seeds.
Inheritance New plants come from single parents New plants come from multiple parents
Plant structures
Parent plants may produce side shoots or tubers.
Plants must produce special reproductive structures such as sori, fruits, or cones.
Vulnerability
Side shoots are usually vulnerable to freezing, so rarely occur in cold places.  (Some plants may produce dormant bulbs which stay underground through winter). Seeds or cones are often hardy enough to endure cold or drought before sprouting in better conditions.
Characteristics Each new plant predictably has the same characteristics as the parent. Each new plant combines characteristics from parents in new, sometimes unpredictable, ways.
Variability
Plant populations have little variability, though there is variability between populations (e.g. types of taro).
There is often a high degree of variability within each plant population.

The high variability of sexually-reproduced plants allows species to adapt to changing environmental conditions, so wild plants most often produce this way. Wild plants can also reproduce vegetatively, and sometimes do so to quickly expand their range, as gingers and bamboo have done in the mountains of O‘ahu.

The high predictability of asexually-reproduced plants make this method very appealing to farmers, who often want to grow new plants that have the same characteristics as the old ones.  Often crops which can be variable in taste, like avocados or mangos or apples, are propagated vegetatively.

Even some “seed crops” are grown from cloned seed produced from tissue culture in labs.  Did you know that most of the corn now grown in the US is genetically identical? Corn traditionally had a high degree of variability (or “agrobiodiversity”) — which allowed it to be adapted to a wide range of climatic conditions — but now modern agribusinesses, that value predictability, encourage farmers to grow identical plants.

Which plants reproduce in which ways?

All wild plants reproduce sexually at some times, though they may also reproduce vegetatively at others.  How can you tell which way it is?  Look at whether the new plants are growing from seeds or in some other way!

Some domesticated plants, i.e. food crops, have been selected for so long that they no longer reproduce in the wild.  For instance, “seedless” bananas and grapes can’t be planted from seed, so they have to be vegetatively propagated.  You can look at list of tropical and temperate foodplants to see which ones are usually grown in which ways.  As you can see, some of them can be propagated either way.

Kinds of vegetative propagation

Plants can be propagated from different parts of the parent plants:

side-shoots: taro (kalo), breadfruit (‘ulu), banana (mai‘a), agave, pineapple, bamboo
slips (apical cuttings): sweet-potato (‘uala), mint, basil
sections of rhizomes, bulbs or tubers: ginger, turmeric (‘ōlena), pia, potato, lilies, garlic, yam (uhi)
stem cuttings: sugarcane (), cassava, malungay, ti (), ‘awa, wauke, plumeria
grafting: avocado, mango, apple, grapes, soursop, citrus

uala ko ulu
Plants propagated by slips (sweet-potato), stems (sugarcane) and side-shoots (breadfruit).

[Illustrations from He mālaʻai kaʻu (I have a garden) from ‘Aha Pūnana Leo]

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Bunchy Top at Ricky's