Biennial bearing (or alternate) bearing is a term used in

pomology Pomology (from Latin , “fruit,” + ) is a branch of botany that studies fruit and its cultivation. The term fruticulture—introduced from Romance languages (all of whose incarnations of the term descend from Latin and )—is also used. Pomol ...

to refer to trees that have an irregular crop load from year to year. In the "on" year too much fruit is set, leading to small fruit size. Excess weight in the main branches can be too much for their mechanical resistance, causing them to break. Another major consequence is that flower induction will be lower, and the subsequent year will be "off" year (too little fruit). The behavior could be due to plant hormones, particularly gibberellins produced in excess in the "on" years in the embryos of the young fruit. It could also be caused by depletion of

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or m ...

reserves in the tree. Biennial bearing is more common in certain fruit crops like mango,

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, where its wild ancestor, ' ...

pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the family Rosaceae, bearing the po ...

, apricot and

avocado The avocado (''Persea americana'') is a medium-sized, evergreen tree in the laurel family ( Lauraceae). It is native to the Americas and was first domesticated by Mesoamerican tribes more than 5,000 years ago. Then as now it was prized for ...

, and is almost nonexistent in

grapes A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years ago, ...

. Biennial bearing is a regular feature of

Arabica coffee ''Coffea arabica'' (), also known as the Arabic coffee, is a species of flowering plant in the coffee and madder family Rubiaceae. It is believed to be the first species of coffee to have been cultivated and is currently the dominant cultivar, r ...

production in

Ethiopia Ethiopia, , om, Itiyoophiyaa, so, Itoobiya, ti, ኢትዮጵያ, Ítiyop'iya, aa, Itiyoppiya officially the Federal Democratic Republic of Ethiopia, is a landlocked country in the Horn of Africa. It shares borders with Eritrea to the ...

and East Africa, and indeed throughout the coffee-growing world. In Biennial bearing a good or excellent (bumper)

crop A crop is a plant that can be grown and harvested extensively for profit or subsistence. When the plants of the same kind are cultivated at one place on a large scale, it is called a crop. Most crops are cultivated in agriculture or hydropon ...

is followed by a poor, low-yielding crop in the next year's harvest. This phenomenon occurs independently of weather and climate, so that even when climatic conditions are favourable for a good crop, the yield can be poor. There can be a fivehold (x5) difference between on and off years, although in extreme cases there can be a tenfold (x10) difference in Ethiopia and areas of East Africa. The biennial cropping rhythm is due to the allocation of the plant's resources: in the productive 'on' year, the coffee tree puts it's resources into producing the crop at the expense of vegetative growth ( stem growth and particularly shoot development and flower

bud In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be spec ...

production); in the 'off' year the plant must make up for this vegetative shortfall, at the expense of flower and fruit production. Biennial bearing may also be a tree's evolved response to manipulating predator populations that may depress the success of germination. This theory is known as the predator satiation theory. Biennial bearing can be reduced or almost eliminated using various means, including

pruning Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots. The practice entails the ''targeted'' removal of diseased, damaged, dead, ...

, the addition of fertiliser, controlled irrigation and the use of selected vigorous clones or cultivars.

Horticultural management

This disorder can be reduced by

thinning Thinning is a term used in agricultural sciences to mean the removal of some plants, or parts of plants, to make room for the growth of others. Selective removal of parts of a plant such as branches, buds, or roots is typically known as pruning. ...

flowers A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanism ...

and young

fruit In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering. Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...

References

{{DEFAULTSORT:Biennial Bearing Agricultural terminology Fruit production Gardening aids