Blackthorn

The advantages of the large-fruited blackthorn cultivars

• Fewer thorns: the large-fruited cultivars have fewer thorns.
• No runners: they are grafted onto the weakly growing St. Julien rootstock and no longer form runners.
• Harvest and process earlier: the new large-fruited cultivars 'Nittel', 'Reto' and 'Godenhaus' can also be harvested in September and October before the first frosts, as they do not necessarily need frost to break down the bitterness and acidity and become edible. This characteristic is most pronounced in the 'Reto' variety. For the other varieties we still recommend waiting for the first frosts or alternatively freezing the fruits harvested early before further processing in order to accelerate the reduction of acids and tannins.
• Larger fruits: finally, the fruits of the cultivated varieties are also significantly larger, reaching about 2 cm in diameter (wild species are approx. 10 mm).

So you have a choice: if you want a primal wild plum that is home to a maximum of nature (insects, birds, butterflies) and almost does not let man through, then you should plant wild blackthorn plants. Ideally, the wild blackthorn then stands in a hedge of sea buckthorn, hazelnut, elderberry and other wild fruits. As a planting distance for a dense hedge (which can also only consist of blackthorn plants) you should choose about 150 cm.

If you like the sweet taste of the sloes and want to harvest fruit regularly for processing, but do not have enough space and tolerance for an overgrown hedge, choose the cultivars 'Reto', 'Godenhaus' or 'Nittel'. Attention: if you plant blackthorn plants, it is best to plant two different varieties, as they are only partially self-fertile and without a pollinator they tend to produce little fruit. Alternatively, plums or prunes can also fertilise their original form, the blackthorn.

Are sloes even edible?

Of course sloes are edible, even if you wouldn't think so when you try to eat the fruit early in September or August. As already mentioned, Ötzi already knew that. Quite a few modern gourmets don't want to do without the characteristic taste, which always includes a bit of astringency and resistance: there are plenty of jams, fruit juices and mixed recipes with other fruits. The production of sloe liqueur is also very common!

Nevertheless, the question of edibility is rightly asked because in the early autumn, especially the fruits of the wild shrubs are inedible, much too sour and too astringent; only after the first frosts do they become softer, juicier, sweet-sour and digestible. With the large-fruited cultivars it is also possible to harvest before the frost, but here too the fruit ripens again after the frost. Alternatively, the not yet fully ripe fruits can be placed individually on a cake tray and frozen in autumn. This ultimately has the same effect as natural freezing, makes the fruit softer, partially dissolves the tannins and softens the taste without losing the characteristic bitter aroma.

Are blackthorn plants poisonous?

The flowers and especially the seeds of the sloe fruit contain the poisonous cyanide glycoside amygdalin, which, however, is neutralised by boiling, so it is not dangerous. The prussic acid content of sloes is generally rather low, it is much higher in almonds and apricots. If the sloes are steeped in brandy during liqueur production, part of the poisonous prussic acid precursor also goes into the liqueur. This then leads to the typical bitter almond flavour, which is the hallmark of the so-called Schlehenfeuer, the popular sloe liqueur. However, the content of amygdalin is so low that it does not pose any danger. In the end, the prussic acid content is less toxic than the alcohol itself. ;-) With both poisons the human body is able to break down small amounts relatively quickly...The problem lies, as always, with the dose...

Blackthorn plants are also poisonous in another sense: their side shoots, which stick out almost horizontally from the branches, have poisonous tips that can quickly sting. This is one of the reasons why folklore and mythology attribute blackthorn plants to all kinds of black, threatening and dangerous things. And really, a sting from a blackthorn, not disinfected, can quickly lead to a painful inflammation, especially on the picking hand. Therefore the tip: always wear firm and safe gloves when handling the blackthorn. And a second tip to calm down: the large-fruited cultivars have far fewer thorns than the wild variety.

The fantastic flowers of the blackthorn plants

Also from mythology and legends, the following story, which is apparently told in Poznan (and on Wikipedia...): the buckthorn mocked the thorns of the blackthorn, who was responsible for the painful crown of thorns of Jesus. But the Good Lord considered the accusation unjust and in order to make amends, he let the beautiful white flowers fall down over the blackthorn to hide the threatening thorns. These flowers, which cover the branches from bottom to top long before the leaves sprout and give off a characteristic sweet almond scent, are really an absolute plus for this primal plum! Incidentally, the flowers, like the fruit, bark and leaves, are also used for astringent teas and infusions, which are said to have antipyretic and anti-inflammatory properties.

Where do blackthorn plants grow and where is the best location?

Blackthorn plants - especially the wild variety - are absolute pioneer shrubs that can easily establish themselves in dry and stony soil and then send out their roots and root shoots to occupy more space. If you buy and then plant blackthorn plants, please note that they love a full sunny to at most semi-shady location, they hate stagnant moisture and prefer a slightly calcareous soil.

Planting blackthorn plants

A full sunny location is even more important for the large-fruited cultivars, and the requirement for a fertile, moist soil is also somewhat greater if there are to be good and high yields. Thanks to the grafting on the St. Julien rootstock, the soil tolerance of the cultivated varieties is greater, from very slightly acidic to alkaline. If the soil is clearly acidic (pH below 6), lime should be added during planting.

We offer the wild form as well as the cultivars 'Nittel', 'Reto' and 'Godenhaus' as strong container plants; the cultivars even as 2-year-old strong plants in 10 L containers. Not only can these blackthorn plants be planted at any time, they are also already so well developed that they usually bloom and bear fruit in the garden in the 2nd year.

If you plant a blackthorn from 1 October onwards, we recommend that you shake out the root ball completely before planting and to remove all of the remaining leaves from the plant. This will ensure that the topsoil is full of roots and that they start growing out immediately. Directly in the topsoil, the sensitive roots (roots are the most “sensitive” organ of the plant) are also less sensitive to warm winter phases than when the entire root ball is planted and the roots have too little time to root out. There is always the danger that the root ball warms up faster than the topsoil in good winter weather and the plant perceives early spring signals and is then damaged by a later cold spell. If you plant blackthorns from spring to the end of September, it is sufficient to tear open the root ball strongly before planting.

The growth

Blackthorn plants form shrubs rather than trees. Also the large-fruited cultivars 'Godenhaus', 'Reto' and 'Nittel', which are offered in the Lubera® Garden Shop and grafted on the St. Julien rootstock, develop into multi-branched shrubs rather than single-stem trees. The growth is correspondingly rather sparse, with the small side branches branching off from the main branches at an angle of almost 90° without a terminal bud, but with a pointed, thorny end. However, there are significantly fewer such thorns in cultivated varieties than in wild plants.

The pollination conditions

Blackthorn plants are only partially self-fertile. So when a blackthorn stands alone, there are only small yields. When planting blackthorns, it is best to always plant two different varieties next to each other, ideally at a distance of 2 - 3 m. Alternatively, it is also possible to plant blackthorn plants near plum and plum trees that are already standing, which they can also pollinate. Bees and bumblebees are then responsible for the actual cross-pollination. Like other insects and butterflies, they appreciate the early grazing of blackthorn.

Blackthorn – the likelihood of confusion

The blackthorn can easily be distinguished from the hawthorn: the blackthorn bloom before the leaves sprout, the hawthorn after. Even with possible poisonous plants, confusion is hardly possible: if you see the plum-like, small fruits of about 1 cm in diameter in autumn and also feel the thorns, you almost certainly have a blackthorn in front of you. Before the frost the fruits taste, as already mentioned, still very astringent; only after the frosts do they become edible.

Pruning blackthorn plants

Well, especially with the wild plants, I understand all too well that one will hardly dare to cut here. That is also largely unimportant, the blackthorn hedge, planted at a distance of about 150 cm, should also become impenetrable. At best, after 10 or more years, such a hedge will be cut back to a stub (10 - 30 cm) in order to renew it and make it more vital again. On the other hand, pruning is very much an issue with large-fruited cultivars, since one wants to harvest as many fruits as possible. For this purpose, old, worn and hanging branches, which also have almost no growth anymore, are cut back to stubs in early spring, so that new fruit shoots can develop.

Blackthorn – where does the name come from?

Blackthorn plants have many names. The fact that they are thorny is not only noticeable on the arms and hands when picking a wild shrub, but the Latin name (Prunus spinosa) already carries the thorns in its name. Why is the blackthorn black? Well, it cannot be the white flowers...The dark bark, however, was used in the Middle Ages to produce ink, which turned out to be not very lightfast and was later replaced. In the age of Snapchat, where pictures and news disappear shortly after publication, such an ink would have its charm. The name “blackthorn”, on the other hand, comes from the Indo-European 'sli', which means 'bluish'. And of course you have to think of Slivovitz, the Czech or Slovakian plum brandy. Because the very hard wood was also used for whips and walking sticks, the nickname 'German Acacia' was probably created, which further extends the colourful circle of names for the blackthorn plant.