How to treat an injured tree?

How to treat an injured tree?

John, Passionate gardener, Cambridge

Guide written by:

John, Passionate gardener, Cambridge

47 guides

Tree injuries can have a variety of causes, particularly on fruit trees. The bare wood, usually protected by its bark, can be attacked by pathogens such as fungi if you don't help the tree to defend itself by covering the wound with a protective layer.

Important features

  • Importance of tree care
  • Type of injury and treatment
  • Monitoring
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Why is it important to care for an injured tree?


A tree injury can be caused by many things: a branch can snap in high winds or if overloaded with fruit; the trunk can be gnawed by animals; cuts, grafts and accidental tool damage during garden maintenance can injure the bark (e.g. careless use of a lawnmower or strimmer).

Unlike animals, trees can't form scar tissue over a wound. Instead, they respond by forming a bulge, sometimes called a cicatricial bulge, but this takes a long time.
To help the tree recover you have to act quickly, since a wound presents an entry point for diseases to invade and propagate, specifically fungal conditions.

Polypores are particularly dangerous. They feed on lignin (an important structural compound in trees) and gradually eat away at the wood without leaving obvious signs until the tree eventually dies. Sometimes, ball-, hoof- or plate-like fungi will appear on the trunk.

Caring for a tree with a broken limb

If the broken branch was already dead when it fell, there's no need to intervene: this is just a normal part of the tree's life cycle which nature knows how to manage. You only need to get involved if the branch was living, and if possible start by sawing the remaining part of the branch off cleanly. Then plaster the saw cut over with healing mastic, using a spatula and making sure you go a little over the edges. If the branch has broken at the level of the trunk, clean the wound with a sickle, removing any wood and bark splinters, and apply mastic as above.

If cracks appear in the mastic as it dries, apply a second coat. For the next few months, take special care of the tree as it will be fragile. Give it some fertilizer or compost and water it plenty if dry conditions prevail.

Making up your own tree healing balm


The truth is, commercially available tree mastics are far from universally accepted, either among tree surgeons or scientists. Their detractors claim that they lock pathogens into the wood, creating a warm, damp environment conducive to microbial growth.

Many gardeners prefer to use a plaster of their own making, which more often than not resembles a traditional French product known as onguent Saint-Fiacre (Saint Fiacre's ointment). This is a mixture of equal parts clay and cow dung, used to treat wounds on fruit trees.

Here's another recipe idea: combine in a container 1 part powdered Bordeaux mixture and 5 parts powdered clay. Gradually add water and stir well to produce a thick paste. You can also add one part vegetable oil to prevent the clay from cracking while it dries. Apply with a paintbrush. You can use any kind of commercial clay for this, or even soil from your garden if you live in a clay-rich area.

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Bordeaux mixture

Is it a good idea to fill hollow trees?


At one time people were advised to fill cavities in the trunks of trees using, shall we say... some pretty barbaric methods. After years of trial and error, it's been established that hollow trees can go on living perfectly healthily for a long period of time.

Tree cavities make very useful shelters for wild animals – which can incidentally be a great help in the garden: bees, woodpeckers, owls, sparrows, bats, squirrels...

The only advice that still stands today is that you should avoid letting water stagnate inside the trunk when the rain gets in. All you need to do is drill a hole with a standard drill below the mouth of the cavity to let the water drain out of the trunk.

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Guide written by:

John, Passionate gardener, Cambridge, 47 guides

John, Passionate gardener, Cambridge

When I was young, I was already working in the family garden. Perhaps that is where my interest in plants and gardening came from. So, it was logical for me to study both plant biology and agronomy.   At the request of various publishers I have, over twenty-five years, written many books on the subject of plants and mushrooms (a subject that is close to my heart).They were mostly identification guides at first, but shortly after they were about gardening, thus renewing the first passion of my childhood.   I have also regularly collaborated with several magazines specializing in the field of gardening or more generally in nature. There is no gardener without a garden, I have cultivated mine in a small corner of Cambridge for the last thirty years and this is where I put into practice the methods of cultivation that will I advise you in as well.

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