Guava is a low-branching fast-growing evergreen shrub that can grow onto a small tree, 3-6m high. Young green shoots are angular. It has pliable branches and smooth peeling bark. The opposite, oblong-oval leaves, 10-15cm long, with serrated margins are smooth and finely pubescent on the upper and under sides respectively. The species is allelopathic and forms a beneficial mycorrhizal association. The root system extends beyond the drip line. It is classified in the Myrtaceae Family which also includes feijoa, pitanga, jaboticaba, cherry guava, hill gooseberry and the many fruiting Eugenia and Syzygium species. There are about 3000 species in the Family and Psidium has approx. 150 species. Taxonomy of the genus is still problematic and although guava is usually diploid there is considerable polyploidy.
Scientific Name: Psidium guajava
Common Name: Guava
How to grow and maintain guava:
It thrives in humid tropical climates up to 1500m elevation but also in sub-tropical areas that don’t have significant frosts. Ideal temperatures and rainfall are 23-28°C and 1000-2000mm pa with distinct wet and dry seasons. The trees may survive drought periods but they stop growing and there can be almost total fruit drop if it occurs during fruit maturation. In colder, more temperate climates, they may briefly lose much of their foliage.
Adapted to a wide variety of soils but poor soils result in lower yields. Best pH is 5-7 and although they will grow above this range, deficiency symptoms for Fe and Zn can be expected. Although they perform best with well-drained soils they can tolerate some water logging.
Flowering and Pollination:
Axillary flowers develop in spring-summer, occurring singly or in cymes of 2-3 on current season or older growth branches. The perfect white flowers, 2-5-3.5cm wide, have 4-5 petals, 200-250 stamens and a single style. The inferior ovary has 4-5 carpels, each containing numerous ovules. They can self-pollinate but if more than one tree is present, cross-pollination can be considerable. Bees are the main pollinators and fruit set can be as high as 90%.
Seeds are used for breeding or to produce rootstocks for grafting as they don’t come true to type. Marcotting and cuttings are also possible.
Commercially, single-trunked trees are preferred for ease of harvesting, but for the home grower, the bush or vase form is favoured. Maintaining light penetration throughout the canopy is important. Heading back branches results in long whip-like growth with low flowering; cutting at forks gives better results. Horizontal branches are more productive than vertical and fruit size is enhanced with fruit thinning.
Seedlings may take 2-5 years to begin flowering, grafted plants less. Depending on climate and conditions, fruit can take 4-6 months to mature. Dessert fruit are usually harvested when half-coloured ripe, and with care as they’re easily bruised. These can then be stored for 2-3 weeks at 8-10°C; at 20°C this reduces to about a week. Well-managed mature trees are very productive and can yield more than 60kg/tree over a staggered harvest season.
Pests and Diseases:
Medfly is the worst pest and will require baiting and spraying to control; thrips and root-knot nematodes may also cause problems. Diseases include anthracnose, made worse in humid environments, with other possibilities being blossom end rot and guava wilt.