Garcinia (Rheedia) gardneriana
Achachairu, bacuri, achacha
Origin
This tropical plant is originally from Bolivia, and has since been spread to Brazil and many other lowland tropical countries.
Climate
Colder winter weather can cause a large drop of flowers and fruit. It fares best with ample rainfall of 1500-2500mm/pa, and in its native environment can tolerate flooding for extended periods.
Plant Description
It is an evergreen tree with a pyramidal canopy that can grow to 5-10m in its preferred environment. It exudes a yellow latex when bruised or cut. Young leaves are pinkish-red before turning yellowish green on maturity. Achachairu is an understory tree and strong sunlight can damage young foliage.
Relatives
Clusiaceae Family with more than 250 species in Garcinia. Taxonomy of the family has been difficult, but Rheedia has now been included in Garcinia (ie it’s a synonym of the accepted name). The difficulty extends to species level and native area locals have assigned both G brasiliensis and G gardneriana to achachairu; fruit available in Australia are most likely gardneriana. The genus includes the highly valued mangosteen, and madrono, gamboge and imbe.
Soils
Like most fruit trees it grows and fruits best in rich soils, but can survive in others with variable fertility. Neutral pH is preferred.
Propagation
Seed is the usual means but they are recalcitrant, so drying is damaging and they are best sown fresh. Germination success decreases with duration of any seed storage. Seedlings need to be protected from full sunlight with shade cloth. With a variable number of seeds per fruit and polyembryony, some seedlings can be clones of the parent with others that may be sexual. Very low success has been found with cuttings and air layers. Grafting is difficult with the latex seemingly hindering effective contact of the cambial layers. Using achachairu as its own rootstock does not produce good results.
Cultivars
There is variation in this species given seed propagation, but no effective systematic selection studies have been reported. Rather, the time-honoured opportunistic selection of seed from good fruiting trees has so far been the main technique of gradual improvement.
Flowering and Pollination
Achachairu is a dioecious species sometimes stated to be andromonoecious. However non-male flowers are structurally hermaphrodite with functionally sterile stamens. Fragrant inflorescences occur as axillary cymes. Male plants have about five times as many flowers per cyme as females, and both have sucrose-containing nectaries as a reward for pollinators. There is a whorl of 10-20 free stamens and staminodes in staminate and pistillate flowers respectively, and in the latter there is a superior globular tri-carpellate ovary surmounted by a central disc-like stigma. Anthesis occurs throughout the morning, with pollination by insects including honeybees.
Cultivation
Little known, but most likely is similar to growing mangosteen.
Wind Tolerance
Not known, but if kept as a small plant should be OK.
Pruning
Pruning is minimal to facilitate harvesting.
The Fruit
The fruit is a berry with a smooth and hard thick skin. It changes from a bluish-green colour when immature to a yellowish-orange and then to orange-reddish colour as it ripens. The skin is thick and bitter, but easily peeled with the fingernails. The flavour is described as something between a feijoa and citrus, sweet and refreshing.
Fruit have an ovoid shape about 4-5cm long with an average weight of 35g. Normally fruit are carried inside the canopy. There can be 1-4 seeds, one sexual and others formed as a result of nucellar embryony, but many of these abort. Together, these seeds comprise a substantial fraction of the fruit. The size of the whole fruit is related to the number of non-aborted seeds.
Fruit Production and Harvesting
Well-managed mature trees can produce a thousand or more fruit per year.
Fruit Uses
They have a sweet, sub-acid flavour when fresh and are normally eaten in this way. Carbohydrate content of the fresh pulp is about 15%.
Pests and Diseases
Fruit fly can be a problem.
Comments
There is now an orchard near Townsville in North Queensland marketing these fruits, and although new to most Australians, their desirable qualities are gradually being recognised.
More Information
Achachairu In Australia
Achachairu is a plant native to tropical south and central America that is included in the genus Garcinia in the Clusiaceae family. Historically the taxonomy of this genus has been a difficult and inadequately studied problem as it includes many species with overlapping and often insufficiently different morphological features that would allow clear species delineation using classical techniques. The problem has been compounded more recently with inclusion of a number of other genera, but it’s hoped that use of modern molecular techniques will help resolve the area.
Currently there are 402 accepted species in the genus globally, with many of these outside the neotropics. It’s likely among the smaller number of currently-listed neotropical species that many of these are actually edapho-climatic variants of individual species and don’t warrant individual status. For example, a recent molecular genetic study in Colombia concluded there were only six native species in that country that were justified as separate and distinct.
An early name for achachairu was Rheedia laterifolia, but more recent taxonomic studies have incorporated Rheedia into Garcinia. The USDA lists G. humilis as a synonym for R. lateriflora, and G. gardneriana as a synonym for R. laterifolia. The Missouri Botanic Gardens have suggested (2017) that fruit available in Australia originally sourced from Bolivia and called ‘achacha’ is probably G. gardneriana (achacha was the common name chosen here for marketing reasons instead of the sth American name achachairu). There doesn’t appear to be any molecular study published in the last 10 years that could help resolve this confusion, so we’re left with a number of possible binomials for achachairu.
The convention in taxonomy is that the most recent and properly approved name should be used with earlier ones being superseded, but in the real world, habits can die slowly and we often see older names still being used. While common names can be confusing and misleading, especially across languages and countries, nailing down binomials is important because we need to know when sourcing information whether it’s applicable to the plants we have – will they grow into big trees, need cross-pollination, can we cross-graft etc. Obviously the sooner we have a thorough genetic study the better we’ll all be. In the meantime however we can speculate that the Australian sourced plants are G gardneriana. There is a taxonomic key for this species, so when we get it to flower and fruit for us in WA we may be able to firm up the hypothesis.