Psidium guajava
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Taxon |
Family |
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Psidium guajava L. |
Myrtaceae |
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| Psidium guajava in its natural habitat Credit: Scott Henderson |
Psidium guajava invading new habitat |
Common names: Guava, lemon guava, yellow guava
Synonyms: Guajava pyrifera (L.) Kuntze, Myrtus guajava var. pyrifera (L.) Kuntze, Myrtus guajava (L.) Kuntze, Psidium aromaticum, Psidium cujavillus Burm. f., Psidium guajava var. cujavillum (Burman) Krug and Urb., Psidium guajava var. guajava, Psidium guava Griseb., Psidium guayava Raddi, Psidium igatemyensis Barb. Rodr., Psidium pomiferum L., Psidium pumilum var. guadalupense, Psidium pumilum Vahl, Psidium pyriferum L.
Life form: Shrub/ small tree
Biology/Ecology:
Dispersal: Seeds mainly distributed by cattle as well as other mammals such as feral pigs, monkeys and rats. Birds also disperse the seeds in some areas. Fruit are sometimes dispersed by flowing water. Plants can regrow from stumps and buds along roots. Introduced by humans for use as a fruit tree.
Reproduction: Plants begin to fruit after 2 to 4 years. The plant produces hermaphroditic white flowers, 1.5 cm diameter. Flowers found singly or in cymes of 2 or 3 flowers. The flowers are pollinated by many insects, especially honeybees (Apis mellifera). The fruit is 5 cm in length and contains many seeds of size 3 to 5 mm. The Psidium guajava tree has been known to produce up to 2000 fruit a year, but normally produce around 450. The plant flowers and fruits all year round.
Herbivores: Goats and sheep graze on leaves. A variety of insects feed on the plant, including fruit flies, whose larvae are often found within the fruit.
Resistant stages: Seeds remain viable for up to a year, but usually for several months. After cutting the tree it coppices and spreads by suckering.
Habitat:
Native habitat: Tropical areas with over 1000mm of rainfall.
Habitat occupied in invaded range: Forests, grassland, riparian zones, especially disturbed areas.
Habitat requirements:
| Altitude | Below 2740 metres above sea level. |
| Light | At least partial sunlight required, prefers full sun. |
| Temperature | Plant grows best in average summer temperatures of over 15 degrees Celsius, but cannot withstand intense heat. Only light frost can be tolerated. Produces more fruit in areas that have a distinct winter season. |
| Annual rainfall | Between 1000 to 20000 mm, although it is drought tolerant. |
| Soil | Tolerates many different soil types, but prefers slightly acidic soils with good drainage. Tolerates soil pH of 4.5 to 9.4, but prefers a range of pH 5 to 7. |
Distribution:
Native to Central America, West Indies and northern South America.
Introduced range: Invasive in southern and eastern Africa, Australia, New Zealand, south-eastern USA, South America, Seychelles, Mauritius and many Pacific Islands, particularly Galapagos, Tonga and Hawaii. Introduced but not invasive in the rest of Africa, Asia, Europe and some Atlantic and Pacific Islands.
Impacts:
Ecosystem: Outgrows native species, particularly when it receives full sunlight. The tree is extensively suckering from its roots. When established it becomes the dominant species by producing dense thickets, suppressing native species. The plant is able to invade undisturbed areas to a lesser degree. It is highly adaptable.
Health, social and economic: Can invade pastureland, increasing the costs of livestock farming. Near agricultural land, it can also be a breeding ground for insect pests such as the papaya fruit fly. However, the fruits produced by the plants are often important to local people, making control a problem.
Management:
Mechanical: Difficult because the plant can regenerate by suckering if the roots are not fully removed. Seedlings and saplings can be dug out. Extensive areas of young trees can be controlled through burning, although in some cases this leads to reestablishment of the species. Large trees can be cut and herbicide applied to stumps. Restriction of cattle movement can reduce its spread.
Chemical: The leaves of one form of guava have a waxy cuticle which limits the effectiveness foliar applications. However, the following methods have been reported as being effective at controlling the plant:
Biological: Goats have successfully controlled the plant in Hawaii by grazing leaves and stripping bark.
References:
Weber, E., 2003. Invasive Plant Species of the World: A Reference Guide to Environmental Weeds. CABI Publishing, Wallingford, UK.
Binggeli, P., 1998. An Overview of Invasive Woody Plants in the Tropics. School of Agricultural and Forest Sciences, University of Wales, Bangor. Available from http://www.bangor.ac.uk/~afs101/iwpt/welcome.shtml (Accessed August 2006).
Henderson, S., 2006. Psidium guajava (shrub, tree). Global Invasive Species Database. Available from http://www.issg.org/database/species/ecology.asp?si=211&fr=1&sts=sss (Accessed August 2006).
Pacific Island Ecosystems at Risk (PIER), 2005. Available from http://www.hear.org/Pier/species/psidium_guajava.htm (Accessed August 2006).
Last updated October 2006
