PLUMS SORT ‘YO YO’
The sort has average growth. It enters full fruition relatively early and has a high and consistent crop. Fruit: big, oval, dark blue with light blue wax bloom. The flesh is crunchy, juicy and has a harmonious sweet-sour taste. The stone separates well from the flesh. The sort is pox and fungus resistant and is very suitable for growing in pox infected areas. The ‘Yo Yo’ plums can be consumed fresh. They can also be processed as well as used as dried fruit. The sort ripens between 30 August and 5 September.
Prunus Domestica L. is part of the sub-family Prunoidae in the family Rosaceae. The tree reaches up to 7 m in height and its leaves are elliptical. The leaf end ranges from hardly to very pointed and its texture is pubescent in various degrees.
August is the month when plums appear on the market with their typical elongated shape and their smooth blue peel, which often turns to purple shades. Prunus Domestica is considerably different than its ‘sisters’ Renglota and Mirabelle plums.
At the start of ripening the flesh is yellow-green with a sour taste. Both gradually transform: the colour to yellow-amber and the taste to rich and sweet. The fruit is relatively juicy; when eaten fresh, the sweet-sour tang can be tasted.
Every year the crop takes place between the 25 August and 25 September when the sugar level in plums is the highest.
Nowadays a big part of the worldwide production of plums is focused on their use as dried fruit. A number to illustrate this tendency is approximately 257 000 tons a year and distinctively rising. More than half of the produce comes from California.
Between 2.5kg and 3.5kg of fresh fruit is necessary to obtain a kilo of dried plums (prunes). The average consumption of fresh fruit per head of population in Europe is around half a kilo a year.
Prunus Domestica was first cultivated in China from where it was brought over to Europe, then later spread to Middle Asia, Egypt and the Mediterranean. In order to preserve its taste all year round, people began using a variety of methods to dry the fruit, dated all the way back to the times of the Roman Empire.
The southern part of Europe is where the sort with its blue to purple colouring finds the perfect conditions for growth: strong sun, rich, crumbly mould and plenty of water.
GROWING OF PLUMS
The plum (Prunus Domestica) is mostly grown through grafting the plum cultivar onto the rootstock of a wild plum (Prunus Americana). The selected seeds come predominantly from the yellow fruit variety, which ripens later. The wild plum grows very well with the cultivated plum sorts, developing a very strong root system and showing a good draught and cold resistance. All types of soils are suitable, from clay soil to poor soil, as long as there is a good drainage. The newly grown plum trees have lush vegetation, longevity of life and high fertility.
Some branch rootstock can be obtained from the wild plum, which then reproduces better through vegetative propagation. Best-known amongst those are the Mirobolan V and the Mariana stock. In some countries damson (Prunus insititia) is used for rootstock because of the medium growth, higher cold resistance and the lower requirements to the soil it passes onto the cultivar.
The seeds of other plum sorts can also be used to grow rootstock. The Pixie rootstock has so far been the weakest amongst the vegetative propagation ones.
The planting distance is one of the factors affecting the intensity of plum produce. The distance depends on the sort’s growth specifics, on the stock, on the technique, and on the type of plantation. When the fruit will be used for processing, the saplings are planted at a distance of 6.5 m to 7 m between the rows and 4.5 m to 5 m within the row and are arranged either by the crown thinning or by a free crown with the height of 90 cm to 100 cm. For the dessert types of plum the distance is 5 m to 5.5 m and 4 m to 4.5 m respectively. They are arranged in the same way, but the height of the trunk is 60 cm to 70 cm forming a hedgerow. After fruit production pruning take place at a height of 3.5 m to 4 m.
During production periodic pruning is necessary both for height and from both sides of the row. This kind of pruning takes place for the trees with high trunks, allowing the reduction of the crown and the encouragement of the branches bearing fruit. Manual pruning is very difficult; these days it is common practice to use mechanical contour pruning with the help of an aggregate after which additional manual trimming is relatively easy.
The main way to take care the upper layers of the plum crops soil is fallow land since most of the trees are grown without watering. As long as there is enough moisture, either natural or through artificial supply, the sod mulch system is another form of taking care of the soil. Aside from its general advantages it serves as an anti-erosion measure for sloped terrains where plum trees are often planted. Other cultures can be grown between the young crops as long as there is wide enough space in the rows and they are regularly treated.
Fertilization encourages fruit production and is therefore particularly important in light of the fact that plum trees are often planted on weaker soil. During the first 3 to 4 years the crops are treated annually with 42 to 48 kg of active nitrogen per acre. Throughout the period of production, in addition to the 48 to 60 kg nitrogen per acre, every 3 to 4 years the trees and the soil are treated with 9 to 15 tons manure, 75-90 kg phosphorus and 105-120 kg potassium. The manure can be replaced by green fertilization or other organic waste. The norms listed here are an estimate and individual numbers should be determined for each crop based on soil and leaf analysis.