Guava

What is a guava?

The guava is a small, tough fruit tree from tropical America. It grows as a single- or multi-stemmed tree up to about 6 metres, with smooth bark that peels in copper-coloured flakes and opposite, strongly veined leaves. It belongs to the myrtle family, the Myrtaceae, like the myrtle of the Mediterranean macchia and the eucalyptus. Its flowers are white with a dense brush of stamens, and its fruit fills a room with its scent when ripe.

Origin and growth

From tropical America the guava was carried throughout the tropics and subtropics early on. It grows quickly, branches low and fruits young: seedlings bear after two to four years according to Morton, after three to eight according to the University of Florida, and they do not come true to variety. Because the tree resprouts readily from the base and the roots, it survives damage that would kill many other fruit trees. The same quality makes it hard to remove once it has escaped.

Requirements

Cold. Young trees may be killed at -3 to -2 °C; mature trees survive short periods of -4 to -3 °C without much damage.

Water. The guava tolerates prolonged drought by pausing growth. For good fruit it needs water during flowering and fruit development. Short waterlogging is tolerated moderately.

Soil. Undemanding, from sand to clay, as long as water does not stand for long.

Light. Sun; in shade it grows lanky and bears little.

Fruit, use and harvest

Guavas are eaten fresh, as juice, jelly or a firm, sliceable paste. The fruit is rich in vitamin C: the USDA database gives about 228 milligrams per 100 grams of raw fruit. Ripe fruit softens and changes colour slightly; it bruises easily and keeps only a few days. Leaves and prunings are useful as mulch.

In many tropical countries guava leaves are a traditional household remedy, above all as a tea for diarrhoea; a review in the Journal of Ethnopharmacology (2008) collects these uses and the laboratory findings behind them. In Japan a guava leaf tea is approved as a food for specified health uses that dampens the rise in blood sugar after a meal. The evidence for this comes from enzyme and animal studies and from a few small human trials, summarised in 2010 by researchers of the company that sells the tea.

In the food forest

In a food forest the guava belongs to the small tree layer: below the tall canopy trees, in sun at the edges or in gaps. Because it tolerates drought and poor soils and resprouts after cutting, it can be pruned hard and repeatedly; the cuttings cover the soil as mulch. In succession it plays the part of a robust early fruit tree that bears while the long-lived trees are still young. Its invasive tendency is the other side of this toughness and needs watching: in a plant guild it should stay where it was planted.

In the Mediterranean climate

Around the Mediterranean, guava is grown commercially in Egypt, among other places, and there the Mediterranean fruit fly is one of its most important pests. A study in the Nile Delta found that fruit infestation peaked at about one fifth of the fruit in August and September. In southern Italy, researchers at the University of Palermo report that a wide range of tropical and subtropical fruit trees can be grown in Sicily if microclimate, varieties, irrigation and wind protection are chosen well. On a plantation near Orosei, about two hours north of Sa Medada, guavas have been bearing fruit for years.

The guava is not on the EU list of invasive alien species, but it is invasive on many tropical islands and in southern Africa, where birds and mammals spread its seeds. Whether it can spread in the Mediterranean is not well documented. Terra Humana deliberately uses some species that are invasive elsewhere, as a method; that is a stance, not an excuse. It means watching where seedlings appear and removing them where they are not wanted.

Propagation and care

Good varieties are propagated by air layering, cuttings or grafting; seed is used for rootstocks. Young trees need protection from frost in their first winters. Pruning after harvest keeps the tree compact and stimulates new fruiting shoots, since the guava flowers on young wood.

How Terra Humana understands it

At Sa Medada the guava stands for a tough, early-bearing fruit tree that can cope with dry summers and hard pruning. It is meant to bring fruit to the planting while the slower trees grow, and to give biomass from its cuttings. Because it spreads easily elsewhere, it is also a plant we observe with particular care.