Prune


(Genus: Prunus domestica, Prubus. Salicina & Prunus simoni - Family: Rosaceae)

 

The prune tree and its origins

Prunes are harvested from a variety of plum cultivars, although not all plum varieties can be used for prunes.  Modern day European varieties mostly stem from the Prunus domestica, which has been cultivated in Europe since 1000AD. However, its wild ancestor, the blackthorn, which predates the prune, still grows freely in the wild today.

The prunus species has many variants of plum and prune which can be traced back to both Asia and Europe.  Depending of the area of origin, the various existing Eurasian species are grouped in 3 categories:

  • European plums (Prunus domestica) to which all the European cultivars belong
  • Syrian plums (Prunus insititia) which includes all damson plums, otherwise known as “plums of Damascus”
  • Mirabolani (Prunus cerasifera) grow wild in Asia Minor and are also used as a rootstock for the apricot.

In addition to the most common varieties mentioned above, there are also the Sino-Japanese plums (Prunus salicina and Prunus simoni) and American plums (Prunus americana).

Cultivars chosen for prunes are denoted by their high sugar content and sweet taste.  They tend to be a freestone fruit which means that the pit or stone will separate easily or will not to adhere to the fruit flesh, perfect for removing the stone when drying the prune.

 

How to Plant Prune Trees

Both plum and prune trees can be evergreen or deciduous and tend to be hardy fruit trees.  Perfect for the novice gardener, they are easy to grow, suffer very little from common plant diseases and you can reap the rewards with rich harvests in a short number of years. 

For best results, plant from autumn through to the end of March, in a medium, deep soil. The soil should be free from excess limestone and well-draining.  A clay based soil is ideal. 

Plant year-old grafts, spacing each 4.5 metres apart; plum trees can vary greatly depending on the cultivar; allow more space if necessary.   When planting, apply a dose of XXXg of XXXX fertiliser and mix well with the earth from the planting hole. 

After 3 years, fertilise the tree with XXXX fertiliser at a dose of XXXX g/m² and repeat three times a year; before flowering, a month before harvesting and again at the end of winter.  Ensure it receives enough nitrogen to guarantee a strong crop. 

Prunes and plums enjoy a temperate climate and exposure to full sun which helps to develop their sweet taste.  If they get too hot, they will never develop beyond small bulbs, too wet and brown rot can become a problem.  They are not suitable for regions that suffer cold winters and late frosts.

Irrigation is essential as soon as the blossom appears.  Water regularly as the fruit grows, taking care not to over-water as this will lead to a poor fruit set, fruit dropping pre-harvest or splitting fruits.

Pruning is essential to produce a rich harvest.  Thin-out during years of high-yielding crops, leaving branches every 10-15 cm.  Removing old wood ensures that the plum tree will produce the maximum quantity of fruit.

Reduce pruning during the dormant period and in summer, remove excess vegetation to direct all the nutrients to the fruit. 

 

When to harvest Prunes

Prune and plum trees are typically in bloom during the spring.  European varieties produce fruits in the summer months and ripen from late July to September.   Japanese cultivars have a longer ripening period and typically ripen between mid June and late October.

The trees are a medium size and reach 5-10m in height; they have a dark grey trunk and branches.  Many cultivars are self-fertile with blooms that feature 5 white petals with serrated leaves.

Plums are harvested as they mature; they are easy to remove from the branch and should be picked before they become too soft, taking care not to remove the bloom that surrounds them.

The fruits range in colour from green to yellow and red to purple, they can vary in shape and size depending on the variety.

 

Propagation of prune trees

Growing from seed or the fruit’s pit can be easier than other methods but often produces inconsistent or inferior fruits.  The most common method of propagation is by grafting.  Combining a strong rootstock with a rich fruit cutting, helps to produce a superior fruit yield.   The plum tree is usually grafted on myrobalan seed or clones of the same. 

 

Did you know?

The prune is most commonly known for its laxative properties thanks to the presence of diphenyl-isatine, a substance that stimulates the intestine. Once dried, the prune has enhanced laxative properties, increased calories, a higher concentration of sugar and minerals but reduced vitamins.

Both the plum and the prune are packed full of other nutrients - vitamin A, B and C, iron, calcium, phosphorus, magnesium, potassium, sodium and manganese.  They are a natural source of energy, a stimulant, a diuretic, a detoxifier and a liver decongestant.  .

In cooking, they are most commonly used in jams, preserves and sauces but also feature in a lot of desserts thanks to their rich intense flavour and sweet taste.