What are examples of secondary roots

White berry mistletoe (Viscum album)

Mistletoe catches the eye in many places, especially in winter. Old fruit trees look as if they were evergreen, as the crown is almost entirely interspersed with mistletoe when it is heavily infested. In recent years, mistletoe has spread widely in the orchards of our region. This fact is due to the insufficient care of old fruit trees.

Numerous myths and legends surround this plant. Protection against evil, remedies in medicine or as a symbol of peace. The stories and traditions about mistletoe are varied and very interesting to look at. As great as it is of benefit to many people and animals, it is just as dangerous for the “orchard meadow” as a cultural asset and the associated ecological factors. By regularly cutting fruit trees, as was common in the past, the spread of mistletoe was automatically reduced.

The absence of these fruit tree prunings, as well as the climatic changes in recent years, form the basis for the now existing problem of mistletoe infestation. Mild winters tempt migratory birds to stay longer in our region. They transmit the mistletoe from tree to tree and thus generate a longer spreading phase. In addition, milder temperatures favor the growth rate of mistletoe on its host tree.

The myth that mistletoe is under species protection and should not be removed should be finally eradicated. The hardwood mistletoe (Viscum album L. subsp. Album), a subspecies of the white berry mistletoe, is not under species protection and does not depend on the apple tree as a host. A wide range of host plants thus ensures the continued existence of mistletoe, which is essential for many bird species such as the mistletoe thrush (Turdus viscivorus), even if we remove it from the orchards. Furthermore, birch, poplar or willow trees are also infested by mistletoe and thus increase the infestation pressure anyway.

The mistletoe is considered a semi-parasite. It penetrates the branch and removes photosynthetically produced assimilates and water from the host tree through a so-called haustorium and weakens the tree to the point of death of the host. Due to the asexual reproduction of mistletoe in the bark tissue (cambium) of the tree, several secondary shoots can develop from the primary plant. This means that part of the mistletoe grows in the branch and is therefore not visible to us.

If the branch on which the mistletoe is visible is cut off, it is essential to pay attention to the secondary roots of the mistletoe in the bark tissue of the host tree. If not all parts of the mistletoe are removed, it will sprout again and react with an even stronger sprout on the tree. Make sure that you cut back the branch so far that no secondary roots (green dots in the sectional view) remain in the branch.

Any tree that is infested with mistletoe should be cut to prevent the mistletoe from spreading. Only if every fruit tree owner takes this fact seriously, the spread in orchards can be contained. Do not start cutting randomly, but try to combine the removal of the mistletoe with a sensible pruning. Divert branches and look for secondary roots of mistletoe in the cut surfaces under the bark. In the best case, no parts of the mistletoe remain in the tree. If this is not possible, new young plants have to be removed again and again in the following years. You can also work with notch cuts.

Very old trees with mistletoe infestation should also be cut. Even if the trees can no longer be completely freed from the mistletoe, this measure reduces the infestation pressure in the stand and thus prevents infestation of younger fruit trees. In the coming months, many fruit and horticultural associations will be offering pruning courses for fruit trees. Here it is shown how fruit trees can be tended and mistletoe removed. A list of these pruning courses, as well as books on fruit tree pruning, can be found on our website www.gartenbauvereine.de under the heading Orchards. This list is also updated on our Facebook page (Verband der Gartenbauvereine SAL / RLP e.V.).

The Association of Horticultural Associations Saarland / Rhineland-Palatinate offers you numerous training courses in the field of fruit growing and horticulture. You can request information about courses and training courses at 06887/9032999 or by email to [email protected]

Do you have an orchard that you can no longer cultivate or are you interested in the topic and want to grow your own fruit? Then visit the orchard exchange of the Association of Horticultural Associations Saarland / Rhineland-Palatinate e.V. at www.gartenbauvereine.de or find out more at 06887/9032999.

Horticultural Association Rhineland-Palatinate e.V.