School Science Lessons
Taro Project
Updated: 2008-03-29
Please send comments to: J.Elfick@uq.edu.au
See also: Interesting Websites
Preface
Before teaching this project, discuss the content of the lessons with a field officer of the Ministry of Agriculture and get advice on planting material, planting distances, site for planting, approved mulch, composting, and control of pests and diseases. Use only the procedures, agricultural chemicals and insecticides recommended by the local field officer of the Ministry of Agriculture. If you cannot control insects by hand-picking, ask the Ministry of Agriculture to recommend a chemical spray. All insect sprays are dangerous. Show the students how to use them safely. Do not get the spray onto your hands. Do not breathe in the spray. Wash your hands well after using spray. Keep the spray container in a safe place where students cannot get it. Spray on a day of no wind but if you must spray when there is a wind, spray down wind. Make sure the spray does not blow on other people.
Taro Project
Table of contents
1. Different kinds of Taro plant
2. Taro planting material
3. Making a taro garden
4. Planting Taro
5. Parts of the Taro plant
6. Taro Leaf
7. Taro corm
8. Taro roots
9. Taro flower head
10. Life cycle of a Taro plant
11. Varieties of Taro
12. History of the Taro plant
13. Helping Taro plants to grow better
14. Diseases of Taro Plants
15. Insect pests of Taro plants
16. Food value of Taro
17. Harvesting Taro
18. Growing Taro for profit
Introduction
Before starting this project, obtain permission from the Principal and consult a field officer from the Department of Agriculture. Teach the first lesson, then plant some Taro with the students. It grows better when planted during the wet season. Although there are four common kinds of Taro plants, this Taro Project refers to "ordinary Taro" (or dalo or talo).When you are teaching about the plant, have that plant in the classroom to show the students.The students must do all the work of planting, looking after the plants, keeping records of how the plants grow, and keeping a record of costs involved in growing them and money received from selling them.
1. Different kinds of Taro plant
See diagram 62.1: Kinds of taro
Show the different kinds of Taro plants in the classroom or visit local Taro gardens to see different kinds of Taro.
Taro is an important food plant in many Pacific Islands like Fiji, Samoa, Tonga, and the Cook Islands. It is also eaten by many people in the Solomon Islands and New Hebrides. The different kinds of Taro plants are in the family Araceae. The aroids are large herbs usually with tubers. They mainly grow in damp places in the tropics. Taro plants are usually pollinated by flies. The corms are roasted or boiled and the starch in them can be made into flour. Some kinds of Taro plants contain calcium oxalate crystals that must be removed during cooking. Taro usually grows in damp soils and can grow in soil that is waterlogged for a time if the water is moving.
The four main kinds of Taro plants:
Taro, "Ordinary Taro" (Colocasia esculenta) (Synonyms: Arum esculentum L., Caladium esculentum (L.) Colocasia antiquorum). The common names include: Arum (India), Ba, Boka, Botika, Cocoyam (Africa), Dalo (Fiji), Dasheen (Egypt), Daun keladi (Malaysia), Eddoe (Africa), Gaui, Malanga (Spain), Mangasiva sasili, Matiotio, Qolquas, Sali, Sika, Tallas, Talo (Tokelau, Tuvalu. Polynesia), Tara, Taro (Cook Islands, Solomon Islands, Polynesia), Tayoba (Spain) Te taororo (Kiribati), Votuki, Wutao. The plant is a staple food in many tropical countries and very popular in the Pacific Islands. 1-2 m tall with underground corms about 30 cm long. It seldom forms flowers or seeds. It has large flat leaves on the end of upright leaf stalks. The leaf stalk or petiole joins the leaf towards the centre of the leaf. Near the ground a thickened rounded corm is produced. Around this plant is a ring of small plants called suckers. Many different varieties occur. Taro grows from sea level up to high altitudes. It grows well in humid places. It can grow in damp soil and under light shade. It is ready to eat in one year.
Swamp Taro (Cyrtosperma chamissonis) is called different names in different islands. It came from Indonesia - Malaysia. In Kiribati it is called babai, in Fiji it is called via kana and in Tuvalu it is called pulaka. It grows to 4 m in height with large leaves that stand straight up. The lower lobes of the leaves are almost as long as the upper lobe. This plant grows very slowly and it only grows in swampy land. This is the main kind of Taro grown by the atoll people in Kiribati, Tuvalu, the Marshall Islands and the Caroline Islands. They may weave baskets around the growing tubers and add chopped leaves to the baskets to act as mulch.
Chinese Taro, "Kong Kong Taro", Tannia, Yautia, "Cocoyam" (Xanthosoma sagittifolium) It grows to 2 m height and has a corm at the base with about 10 lateral tubers or cormlets (cormels). It is common in the Cook islands and Tonga and less common in other islands. In Fiji it is called dalo ni tana and in the Cook Islands it is called Taro tarua. Instead of making one big root or corm it makes many small cormlets. The leaf is quite different in shape from ordinary Taro and the leaf stalk is joined to the edge of the leaf, not to the underside of the leaf.
Giant Taro, wild taro, kape, elephant's ear (Alocasia macrorrhiza) is not usually planted but grows wild in the volcanic islands. It is a large erect herb 3-4 m tall with a stout permanent stem. It was cultivated in eastern Asia. In Fiji it is called via kau. The food part grows above the ground. The split between the upper lobes of the leaf goes right down to the junction with the petiole or leaf stalk. It is not popular because the food part contains calcium oxalate crystals that must be removed during cooking.
2. Taro planting material
See diagram 62.2: Taro planting material
Show examples of the different kinds of planting material in the classroom.
Taro can be planted from three kinds of planting material:
"Tops" are the leaf stalks with a little of the top of the Taro root. This is the most common planting material. Bigger tops are better than smaller tops because they have more stored food and usually produce a bigger Taro. The best tops are 6-7 cm wide at the base.
"Suckers" grow from the sides of the Taro root or corm. They are good planting material. Use the biggest suckers because they have more stored food. A taro grown from suckers has a pointed base but a taro grown from tops has a flat base.
"Runners" runners grow out from the corms and run over the surface of the ground. These runners make shoots that can be used to plant the taro.
3. Making a taro garden
See also 6.9.14 Composting
Chose a place for the taro garden. It should be a flat place, about 8 X 8 metres, near running water and where the soil is damp.
Dig the garden area twice with two weeks between diggings.
4. Planting Taro
See diagram 62.4: Planting Taro
For an 8 X 8 m garden you will need about 200 pieces of planting material - tops or suckers. Plant the tops 60 cm apart and about 30 cm deep. In some places the people plant the Taro with a digging stick. After making a hole they plant the Taro top, but they do not cover the hole - they leave it open. Is this a good practice? Some people say this is not a good idea and the hole should be filled in after planting the taro.
5. Parts of the Taro plant
See diagram 62.5: Parts of the Taro plant
Show whole taro plants into the classroom. Use the diagram to show the different parts of the plant:
fleshy corm k male flowers
b base of the corm l sterile appendage
c bud on the side of the corm m base of a leaf stalk or petiole
d bud growing into a cormlet n petiole or leaf stalk
e sucker growing up from a cormlet o top of the petiole
f runner growing from a bud near the top of the corm p leaf spot, only in some varieties
g shoot growing from a runner q dark streaks on leaf, only in some varieties
h unopened flower head r midribs of upper leaf lobes
i opened flower head s rounded tips of upper leaf lobes
j female flowers t pointed lower leaf tip
6. Taro Leaf
See diagram 62.6: Taro leaf
Show Taro leaves in the classroom.
The Taro leaf has a large flat lamina, and a long tapering leaf stalk or petiole.
The midrib runs from the petiole to the leaf tip. It is seen mostly on the underside of the leaf.
Two smaller midribs support the upper lobes of the leaf.
In some taro varieties there is a dark spot on the topside where the petiole joins the leaf.
Side veins run from the midrib to the edge of the leaf.
Very small veins pass from the side veins into the lamina of the leaf.
In some varieties, dark marks may be seen on the leaf, especially near the midribs of the upper lobes.
Because the lower tip of the leaf is pointed, it is a "drip tip". This means that water that has washed over the leaf may stop here before dropping off the leaf. This water may bring to the tip some oxalic acid that is in the leaf. That is why if people are going to eat the leaf, they first pull off the tip that contains more acid.
The leaf stalk or petiole has three main parts:
broad lower base part,
middle part,
upper end that joins the leaf and is usually bent over.
The colour of the petiole is important, for this is the chief way of telling one taro variety from another. The colour may be pale green, green, dark green, purple or red. It may have red, brown or dark green streaks on it. The colour of the base may be green, white or red. The top may have a different colour on its upper side or underside.
Cut across the tops of a taro plant. The petioles are all in different positions so that each leaf will be held out to the light in a different position and will not shade the leaf next to it.
7. Taro corm
See diagram 62.7: Taro corm
Show Taro corms in the classroom.
The part of the taro you eat is called a corm. It is really an underground stem swollen with stored starch. Like other stems it has these parts:
The growing point or a shoot apex. To see the growing point, use a knife to cut down through the leaf stalks and the corm. The shoot apex is a rounded part that goes up into the base of the leaf stalks. Another way to see it is to pull off the leaf bases of the petioles until the rounded dome of the shoot apex can be seen.
Many leaves joined to the shoot apex. As the corm grows the older leaves die and drop off and new leaves are made.
A leaf scar is a place where a leaf was joined to the corm but has now fallen off. The leaf scars are seen as circular marks that go around the corm.
Axillary buds form just above the place where the leaf was joined to the stem. The axillary buds can grow into little corms or "cormlets" (cormels). The cormlets can grow into suckers that may be used as planting material.
The shape of the bottom of the corm tells us what kind of planting material was used. If it were grown from tops, the base of the corm will be flat. If it were grown from a sucker, the base of the corm will be pointed.
8. Taro roots
See diagram 62.8:  Taro roots from a top
Show Taro roots in the classroom. The easiest way to see taro roots is to plant a top and then dig it up after a week.
See a ring of white roots growing from the base of the top. As the corm grows upwards, most of the roots are usually up near the top of the corm. When the taro is nearly ready to harvest there may not be very many roots left on it.
Show roots growing from a top that has been recently planted. Dig gently around a taro plant to find some roots.
9. Taro flower head
Show an unopened and an opened flower head in the classroom. Taro flowers are seldom seen, but they are interesting. When the taro plant has grown to full size, it may make a head of flowers. This is not important because it does not usually make seeds and they cannot be used for planting. When the flower head first appears, it is enclosed by a large leaf-like wrapping called a spathe. Later the spathe will open and then the small flowers will be seen growing on a central stalk. The female flowers are form lower and the small male flowers are formed further up the stalk. At the end there is usually a small piece of stalk that has no flowers on it. Flowers may have bad smell to attract flies that pollinate them.
10. Life cycle of a Taro plant
See diagram 62.10:  Life cycle of taro
Show examples of the different phases in the classroom. As a taro plant grows, it passes through three different phases:
Establishment phase
During this phase the plant is making its first roots and forming its first leaves. At first the leaves are rolled up into a tube, but later they unfold as the fast growing petiole carries them upwards. During this phase it is important that the soil is kept moist. This is why the people in the Cook Islands cover the surface of the soil with dead coconut or other leaves to act as a mulch. The establishment phase lasts about eight weeks. During this phase the corm does not grow much.
Vegetative or leaf making phase
This phase starts when the taro is about eight weeks old, and it lasts for about three months or when the plant is 20-24 weeks old. The plant must have many leaves to make much starch for the corm, so during this phase:
the number of leaves increases,
the height of the leaves increase also so the plant gets higher,
the corm starts to grow upwards, but at first it only grows slowly.
Maturity phase or storage phase
This phase occurs when the taro plant has grown to its greatest height. This phase usually lasts from 20 to 40 weeks. During this phase:
the height of the leaves gets lower,
the number of leaves grows less,
the corm grows bigger quickly.
At this time all the starch made by the leaves moves down to the corm where it is stored. At this time also, fewer roots form so there may be very few roots on the taro when it is harvested.
At what phase are the taro plants in the school garden, in the village gardens?
11. Varieties of Taro
See diagram 62.11: Varieties of Taro
Show different varieties of taro in the classroom or visit village gardens to see varieties of taro.
In some places there are only one or two varieties of taro because disease has killed off most of the other varieties. Yet in places where taro plants grow well, there are many varieties, e.g. about 70 varieties in Fiji.
What are the differences there are between local varieties of taro?
What are the names of the local varieties and how to recognize them?
Taro varieties may differ in many ways:
The petiole may be red, purple, green or streaked. The streaks on the petiole may be dark green, or brown, or purple or white and red.
The top of the petiole may be a different colour from the middle of the petiole, or it may have a special colour on top or underneath.
The base of the petiole may be paler, or white or pink.
The corms may be single or they may be branching.
The middle of the leaf may have a purple spot where the petiole joins it.
The top of the leaf lamina may have a dark coloured streaks.
The size of the corms and the yield may vary.
The amount of water in the corms may vary. Some corms have much water and are called "soft" taro. Some corms have less water and are called "hard" taro.
The colour of the corms may be white, grey, yellowish, purple, or pink.
The length of time for growth to maturity may vary. Some taro varieties are ready to harvest in six or seven months. They are called "quick maturing" taro. Some varieties take eight months before they are ready for harvest. They are called "medium maturing" taro. Some varieties take nine or twelve months before they are ready for harvest. They and are called "late maturing" taro.
Some varieties make many suckers but others make very few suckers.
Some varieties make runners that grow over the surface of the ground, but others never do this.
Some varieties need a very wet place to grow, but others can be grown on drier land.
Some varieties easily get infected with diseases but others never get these diseases.
12. History of the Taro plant
Taro plants probably came from Southeast Asia where it still occurs wild. From there it was taken to China or Japan .At the time of Christ, taro plants were was reported growing in Egypt where they are still grown. From Egypt it spread to Mediterranean countries and to Africa, especially to the forest areas of West Africa and the West Indies. About 2000 years ago when taro plants were being taken west to Africa, it was also taken eastward to the Pacific Islands. From the Central Pacific taro spread to Tahiti and from there to New Zealand, Hawaii and the West Indies. Taro plants have different names in different parts of the world that reflects the history of taro.
13. Helping Taro plants to grow better
The energy needed to make the food in the taro root comes from the sunlight. When the leaf uses this sunlight energy and turns it into stored food energy, some energy is always lost. Energy is lost in different ways:
The soil does not have the required plant foods or there is not enough water in the soil.
The taro plants are infected with a disease or insect pests eat the leaves.
The taro plant is not the best variety for that place. Ask a field officer form the Department of Agriculture to advise on the best varieties to grow.
The taro plants are not given good care and are not weeded properly.
How can you make taro plants grow better by controlling the energy losses?
After controlling energy losses you can make taro plants grow better by adding plant food to the soil. Plant foods can be put into the soil in three ways:
Put fertilizers in the soil. Ask a field officer from the Department of Agriculture to recommend a suitable fertilizer for taro. Taro plants need potash. In some places taro is fertilized with a 6:9:8 mixture of ammonium sulfate, superphosphate and potassium sulfate. Do not use too much fertilizer and do not put it too closer than 10 cm to the plants. One matchbox full for every square metre of soil may be enough.
Make compost and put it on the soil near the taro plants. The best kind of compost includes animal manure. Ask a field officer from the Department of Agriculture to advise on the use of compost. In some place mulching taro is NOT recommended because the mulch may contain the larvae of the Taro Beetle.
Green manure. Dig into the taro garden some legume plants, e.g. Siratro or Desmodium or Cowpea. The rotting legumes will add nitrogen to the soil.
14. Diseases of Taro plants
$Show different examples of diseased taro plants in the classroom or visit village gardens where diseased plants occur.
Taro Leaf Blight fungus (Phytophthora colocasiae)
Classification: Myceteae: Mastigomycota: Diplomastigomycotina: Oomycetes: Peronosporales: Pythiaceae: Phytophthora
Other names: Taro Blight, Leaf Blight, Phytophthora Leaf Blight, Yu Yi Ping (China)
The Taro Leaf Blight fungus produces small round watery spots that get bigger. Later these rotten areas may get larger, especially near the tip of the leaf. During the day the spots dry and contain a white powder. The taro plant produces a clear liquid at the leaf tips from a structure called a hydathode. Producing liquid from leaves is called guttation. The liquid dries to form brown pellets where the spores of the Taro Leaf Blight can survive dry conditions. Taro Leaf Blight may be spread by runoff water along the path of drainage. Planting material may be infected and become the source of the disease.
Control of the disease:
Use only healthy planting material.
Do not use planting material infected with the disease from the previous year.
If the disease occurs, observe how it spreads then think of ways to control it, e.g. change to surface drainage may control further spread of then disease.
Plant the taro plants further apart so the disease cannot move so easily from one plant to another.
Spray the plants with Bordeaux Mixture. It is a mixture of copper (II) sulfate and calcium hydroxide or slaked lime.
Viruses cause diseases that may make light and dark streaks on taro leaves, or may make the leaves die. The only way to stop these diseases is to dig out diseased plants and burn them. Then the disease cannot spread to other plants.
15. Insect pests of Taro plants
See diagram 62.15: Insect pests of Taro plants
Show examples of insect pests of taro plants in the classroom or visit gardens where insect pests occur.
Taro Beetle, Babai Beetle (Papuana huebneri and Papuana uninodis)
Classification: Coleoptera Scarabaeidae
The adult beetles of Papuana huebneri are serious pests of taro and other plants, e.g. Chinese Taro Xanthosoma sagittifolium, oil palm, young coconuts, bananas, sweet potato, pit pit and a fern Angiopteris. The adults can make the plants wilt and die. They enter the stalks and bore down into the corms, making 10 mm diameter tunnels. They give a sour taste to the corm.
In the Solomon Islands, Papuana uninodis adults burrows into the corm below ground level base. The larvae may live in the coconut roots, but may not cause damage. The adult female lays eggs deep in the soil. The larvae hatch as white curl grubs. They eat rotting vegetation so they can live in mulch, cow dung and garbage tips. They form a pupa in the soil. The adult emerges about 20 weeks after the egg was laid and lays eggs after about 7 weeks. The adults move about at night and live for up to one year. No insecticide can control this pest.
Taro Hawkmoth, Silver-striped Hawkmoth, Schwärmer, Gabi Moth (Hippotion celerio) (Classification Lepidoptera Sphingidae) The taro hawk moth caterpillar that may cause the taro leaves to die off.
16. Food value of Taro
Taro corms do not store well. They will only keep for about two weeks. If they are put into plastic bags, or refrigerated, they may keep longer. Some varieties have less water and more starch food. It contains much starch, so is a very good energy food. It contains almost no fat and little protein. There is not much fibre, so the food is easily digested. The following table shows the percentage of different substances in taro corms:@@@

Starch 13 to 29%
Protein 1.4 to 3.0%
Fat 0.2 to 0.4%
Fibre 0. 6 to 1.2%
Minerals 0. 6 to 1.3%
Vitamins B and C  not present
@@@
17. Harvesting Taro
When the taro plants are ready for harvest, they can be dug up a little at a time or all dug up and sold in a market.
Dig up the taro plants then cut off the leaf stalks about 90 cm in length.
Sell the taro crop in the market.
Record the following information:
Total weight of the taro crop harvested and total weight sold
Costs of growing the taro crop
Separate costs into:
Production costs, which would have to be paid again next year, and
Establishment costs, which would not have to be paid again for, say, five years.
Divide the establishment costs by 5 and add this the production costs to be the total cost.
Total receipts from selling the taro crop
Profit = total receipts from selling the taro crop - production costs - establishment costs/5
18. Growing Taro for profit
See also 6.9.20.0: Understanding the records
Students could try growing taro for sale in the local market. They should decide how much land they would need and how much taro they think they could look after. If they know how much money came from the small taro garden at the school they can calculate out how much money they could make each year in their garden.
Show students how to make a budget for a taro project.
How much land would they need?
How much money would they have to spend as costs to buy things needed to grow the taro?
Students must watch the growth of the taro plants in the taro project and keep records of how the crop grows.
History
These teaching materials were originally written and illustrated by Mr J. A. Sutherland, Faculty of Education, University of New England, Armidale, Australia and later edited by Dr J. Elfick, School of Education, University of Queensland, Brisbane, Australia.