Hi @karaho
Thanks for your question. They are rather weird aren't they those tentacles coming from your apple tree.
Don't panic though; these weird growths are known as burr knots.
What's a burr knot?
A burr knot is a form of adventitious root that can appear on the trunks of trees and shrubs. They look like strange worms or fingers coming from the side of fruit trees and can cause gardeners to panic that some alien life form has taken over their plant. But don't worry it's just a harmless phenomenon.
These fingers are plant cells that are dividing and then transforming into root tips, just not underground!
Its a phenomenon that happens frequently on grafted fruit trees above the root stock. As these root stocks have been chosen due to their high rooting success, rather this can then be passed on to the scion above the graft which can then start to root further up the tree. Meaning it's just a hangover from the overly zealous root stock in most cases.
Adventitious roots are root that form from any non-root plant tissue such as leaves, stems etc. You can often find them on woody climbing plants that may get covered in moss causing an breakout of adventitious roots in the form of 'air layering'.
What causes burr knots
Burr knots are caused by environmental factors such as a damp environment, low light and warmer temperatures. I often find that fruit trees with leaf fall allowed to build up near the base causes burrs or fruit trees in protected, warm corners of a walled garden.
These burrs can be used to propagate a fruit tree by bending over the branch and allowing it to root. This is an old practice which has since been moved away from to grafting.
https://youtu.be/DFdcQU8sNx8
Are burr knots fatal?
No they are not. Though they may take valuable energy away from fruiting and other tree growth. Burr knots can cause weakness in the tree where knots are present and allow infection to get in. So it's vital you keep good plant hygiene with them. Clean sharp secateurs and cleaning off any fungus, rust or bird poo from these roots.
How to prevent burr knots?
Clearing vegetation from around the fruit tree is a good idea, by strimming. Keeping any grass or lawn at a low level. Also if you've used a tree guard, sometimes this can cause burr knots as the humidity behind the sleeve is higher. You can cut off burr knots with a shape knife or secateurs but do so in spring when the wound can heal quickly.
https://youtu.be/jQUHwhhOPKM
Even my orchard has a grafted fruit tree with burr knots. To no detriment.
I would leave them alone, unless they make contact with the soil. They will probably just slow down and sit there as knobbly bumps!
Hope that helps!
Lee
Hi @karaho
Thanks for your question. They are rather weird aren't they those tentacles coming from your apple tree.
Don't panic though; these weird growths are known as burr knots.
What's a burr knot?
A burr knot is a form of adventitious root that can appear on the trunks of trees and shrubs. They look like strange worms or fingers coming from the side of fruit trees and can cause gardeners to panic that some alien life form has taken over their plant. But don't worry it's just a harmless phenomenon.
These fingers are plant cells that are dividing and then transforming into root tips, just not underground!
Its a phenomenon that happens frequently on grafted fruit trees above the root stock. As these root stocks have been chosen due to their high rooting success, rather this can then be passed on to the scion above the graft which can then start to root further up the tree. Meaning it's just a hangover from the overly zealous root stock in most cases.
Adventitious roots are root that form from any non-root plant tissue such as leaves, stems etc. You can often find them on woody climbing plants that may get covered in moss causing an breakout of adventitious roots in the form of 'air layering'.
What causes burr knots
Burr knots are caused by environmental factors such as a damp environment, low light and warmer temperatures. I often find that fruit trees with leaf fall allowed to build up near the base causes burrs or fruit trees in protected, warm corners of a walled garden.
These burrs can be used to propagate a fruit tree by bending over the branch and allowing it to root. This is an old practice which has since been moved away from to grafting.
Are burr knots fatal?
No they are not. Though they may take valuable energy away from fruiting and other tree growth. Burr knots can cause weakness in the tree where knots are present and allow infection to get in. So it's vital you keep good plant hygiene with them. Clean sharp secateurs and cleaning off any fungus, rust or bird poo from these roots.
How to prevent burr knots?
Clearing vegetation from around the fruit tree is a good idea, by strimming. Keeping any grass or lawn at a low level. Also if you've used a tree guard, sometimes this can cause burr knots as the humidity behind the sleeve is higher. You can cut off burr knots with a shape knife or secateurs but do so in spring when the wound can heal quickly.
Even my orchard has a grafted fruit tree with burr knots. To no detriment.
I would leave them alone, unless they make contact with the soil. They will probably just slow down and sit there as knobbly bumps!
Hope that helps!
Lee
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