Fruit thinning

When integrated within an organic approach, fruit thinning is a useful task which ultimately improves the resilience and vigour of plants. Skilfully applied thinning will help to maintain soil fertility by stabilising the seasonal demand and take-up of important minerals and organic nutrients. It can also enhance the quality and flavour characteristics of each mature crop. Because selective breeding and biotechnology now dominate many aspects of mainstream fruit production, fruit thinning is less commonly practiced and has even been marginalised within the organic sector for many common fruit species. With their ability to manipulate key characteristics of the reproductive cycle, agricultural scientists have developed plants which can produce reasonably fixed quantities of fruit each year. While this provides a high degree of predictability and convenience for some large commercial growers, there are problems associated with the short sighted approach and practices encouraged by these new technologies.

The traditional purpose of fruit thinning was to conserve resources and extend the useful life of plants. This made intuitive sense when fruit trees or vines were considered to be an expensive capital investment, to be carefully maintained and improved over an extended period of time, typically several decades. Compare this long term and sustainable approach with those currently encouraged by the biotech and agricultural research conglomerates. In the realm of fruit production, biotechnology firms are looking to design plants which mature quickly and produce annual crops with a minimum degree of physical effort.

Instead of focusing on organic nutrient replacement and the development of healthy soils, the emphasis is placed upon the plants themselves. On account of their altered characteristics, many trees will be treated with multiple chemicals to control their rapid development and productive output. Instead of progressing through a complete lifecycle, some of the altered plants produce sterile fruit, with seeds that can never sustain new life. This underlies an important component of a current economic strategy which involves securing exclusive patents for modified fruit varieties. At some point in the future, this practice may restrict the availability of fruit varieties which fail to meet the imposed criteria.

From the organic and holistic perspective, fruit thinning is linked with the need to integrate soil fertility, plant development, and crop delivery. This requires preparation based on a practical awareness and application of those natural cycles which support sustainable biological replenishment and renewal. Most fruit varieties take at least several years to mature, with an ability to slow or increase their rate of development according to climate, soil conditions, and related environmental factors. In some situations, early fruiting can result in plants with stunted growth, reproductive defects, and low resilience against disease and pestilence. When left to ripen, it is the seeds inside the fruit which exhaust the immature plant. Seeds contain a concentrated supply of protein, fats, and minerals. When fruit is allowed to develop, the immature plant must obtain these nutrients from the soil and expend additional resources to enhance the functional capacity and protective environment for each seed.

With the exception of cherries, pears, and some older citrus varieties, most of the tree fruits will produce higher quality crops when they are thinned before seasonal maturity. Most sources recommend an aggressive approach, with the early removal of at least half the emerging crop. In naturally dry conditions, the remaining yield of fruit will decrease substantially in weight but is more likely to develop intense flavour characteristics. This is particularly the case for olives, grapes, apricots, and tomatoes and figs to a lesser extent. For other well known species such as plums, apples, and peaches, the fruit left after thinning tends to grow larger so the total yield will not necessarily be decreased in weight. A large percentage of the additional weight will be water, however, when care is taken to maintain soils with sufficient organic material, there is likely to be some increase in the overall quality and flavour characteristics of the thinned crop.

Under natural growing conditions, some mature fruit varieties will crop in alternate years. In order to encourage production every year, some growers will deliberately remove at least half of the emerging fruit during the initial and subsequent cropping seasons. To achieve the best result, thinning should always be carried out before the fruit is half grown. With early attempts, this practice is more than likely to promote uneven crop yields. Over time, a consistent approach to fruit thinning can enable seasonal crops to become balanced and regular. The eventual outcome, however, will always depend upon the overall condition of individual trees, and the suitability of local growing conditions.

Another important reason for thinning fruit is to prevent isolated occurrences of disease and pest from becoming established within a crop. Many species of fruit tree and vine are susceptible to bacterial and viral infections, along with a wide range of insect pests. In order to cause significant damage, plant diseases must be maintained on a permanent or temporary host. Any infected tree within an orchard represents a serious situation because the disease pathogens are most likely to have become established. In most cases, the introduction of disease begins with a temporary host. Plant diseases can survive from one growing season to the next in localised and sporadic clusters.

Infected plant materials including fruit, must be removed and destroyed to prevent the risk of host permanence, and a widely distributed range of incidence. In addition to keeping the ground clear of debris such as kitchen scraps, animal faeces, plastic containers, and insect larvae, it is important to periodically inspect the plant itself and to carefully remove any fruit which appears bruised, ripe, mottled, or misshapen in any way. Sometimes there will be clear evidence of problems, such as the deformed shapes and blistered patches on apples affected by fungal scab. On many occasions, however, there are only subtle indications which may pass unnoticed until harvesting time. The best approach is to consult local fruit growers who have gained sufficient knowledge and experience to identify the early signs and symptoms.