The magical cherry blossom heralds the most beautiful time of spring. What follows are tasty fruits, which of course taste best when freshly harvested. The cherry is one of the most popular types of fruit in Germany. However, it is not uncommon for the cherry tree to become resinous, which is reflected in an amber-colored, sticky discharge. This can have various causes that should not be underestimated.

Resin flow – symptom rather than disease

Sap or gum flow is not a disease but a sign of weakening of the tree. This is a very common phenomenon in Prunus species, which also includes the cherry. Individual branches or the entire tree can be affected. There are veritable foci from which the rubbery mass emerges.

The causes for this can be parasitic or non-parasitic in nature. In some cases they are still unclear. What is certain is that certain factors can favor the occurrence of this resinous discharge, such as fungal infections, unfavorable growth conditions or mechanical damage. It is therefore important to identify and eliminate the exact cause. The tree can only recover if the polluter is found and eliminated.

drought stress

Drought stress occurs after long dry and hot phases, the tree no longer gets enough water. Even though trees withstand dry periods better than other plants thanks to their deeper-reaching roots, prolonged drought is problematic. Natural rainfall is often insufficient.

At the latest when the leaves begin to droop or are already discolouring, you should water regularly. Wrinkled fruits are also a sign of a lack of water. During periods of drought that last longer than a week and are accompanied by heat, it is advisable to water daily, about one to two buckets of water, depending on the size of the tree. Rainwater or service water should preferably be used for watering. But you shouldn’t overdo it, because that can promote fungal diseases.

Tip: If the cherry tree is resinous, you should remove affected branches and twigs. The best time to do this is usually mid-February to early March.

Late blight

Another cause of the so-called gum disease can be late frosts. The cherry blossom begins around May and the Ice Saints take place from the 11th to the 15th. May instead. Precisely on these days, cold days with night frosts can still occur. The tender new shoots are at risk, but especially the flowers.

Even a single night of frost can kill them. In addition, the high temperature differences between day and night in spring can lead to frost cracks that can go deep into the wood. After such frost damage, resin can also escape from the bark in seemingly healthy areas.

Tip: Protecting a tree from frost is difficult. However, when planting, you can make sure that the location is as sheltered as possible.

Unfavorable site conditions

Even with unfavorable site conditions, it can happen that the cherry tree resin. Heavy and dry, sandy soils that tend to waterlogging can promote resin flow. The pH value is important because cherries are more susceptible to acidic soil than to neutral to alkaline ones. The nutrient content of the soil plays an important role. If this resinous discharge occurs, over-fertilization with nitrogen can be just as responsible as a lack of potassium, phosphorus or lime.

Tip: If you suspect the cause in the nature of the soil, it is advisable to carry out a soil analysis and then improve it accordingly.

Error in cutting

Pruning too soon, too late, or improperly can also be responsible for the cherry tree losing resin. Because there are a lot of things that can go wrong when it comes to editing.

  • Do not divert stronger branches to side shoots that are too thin
    • result in strong juice pressure and rubber flow
  • If possible, do not direct the side shoot directly
    • it is better to leave a cone about 20 cm long
    • Resin flow then occurs at the spigot
    • it dies after some time and can be removed
    • Lateral shoot is preserved
  • cut out sharp-angled branches that are close together in young trees
    • otherwise tensile stress in the crown is too great, the tree is resinous
  • when pruning, cut back the relevant shoot to a weaker side shoot
    • he takes over the function of the tip
  • Preferably cut cherries in winter
Note: Careful wound care is essential for any cutting measures.

Parasitic causes and how to combat them

The parasitic causes of gum disease, or gummosis, include various diseases of the bark caused by fungi or bacteria. In the case of cherries, these are Monilia peak drought, Valsa disease and shotgun disease .

Monilia peak drought

  • mainly occurs with morello cherry (sour cherry).
  • Leaves, flowers and young fruits turn brown and wither
  • Gum flow occurs at transitions from healthy to diseased tissue
  • Prune affected shoots back to healthy wood

Valsa disease

  • individual shoots and branches die off suddenly
  • on dying shoots, numerous cracks in the bark
  • Cherry reacts with resin flow
  • Generously remove affected parts
  • always cut outside of the main infection period

shotgun disease

  • punctured leaves, indication of shotgun disease
  • on infected young shoots, brown spots with a reddish edge
  • Gum flow droplets may leak
  • Thin out the treetop and spray


In addition to fungal pathogens, a pest can also cause the cherry tree to become resinous. What is meant is the bark moth, in particular its larvae. As the name suggests, it burrows under the bark. It affects almost exclusively the trunk area. Its larvae sit under the bark or bark, at the grafting point and on the bulges of wounds. A recurrent infestation can cause significant damage, most often associated with rubber flow.

Appropriate countermeasures should be taken as early as possible. Otherwise there is a risk that large parts of the tree will die. In order to do justice to this, one should not only pay attention to obvious resin flow, but also regularly check for possible fungal or pest infestation.

preventive measures

  • prevent by buying hardy or resistant varieties
  • pay attention to a protected location and suitable soil
  • avoid frosty and damp locations
  • Cherry trees like permeable, deep, rather calcareous soils
  • adequate supply of water and nutrients
  • water regularly during dry periods in summer
  • Avoid using nitrogenous fertilizers as much as possible
  • Treat fungal diseases as soon as possible
  • Combat bark moth infestation immediately

In general, regular and professional pruning and thorough disposal of the clippings can prevent diseases and curb an existing infestation.

Tip: Among the cherries, the varieties ‘Burlat’, ‘Regina’, ‘Cerema’ or ‘Corund’ are particularly hardy.

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