I see this term being used all the time in regards to maples...."This is a very unusual compact dwarf upright discovered as a witch's broom growing in a 100+ year old red maple cultivar." What does that mean exactly? Thanks, Peter
Witches Broom
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Bonsai Nut
Nuttier than your average Nut
Witches' brooms are nodes of growth on a tree that result in a ball of growth with short internodes and many branches all erupting from the same point (it doesn't really remind me of a broom, but that is the source of the name). The cause of this abnormal growth can be environmental (fungal / pest) or genetic. In the case of genetic cause, it is sometimes possible to propagate material from the witch's broom than retains the same characteristics (dwarf growth / short internodes).
Here is a good article with images.
An example for bonsai is the JBP cultivar Pinus thunbergii "Kotobuki Yatsubusa". All yatsubusa JBP came from a witch's broom on a kotobuki. Here is a photo of the mother plant:
You can see the yatsubusa witch's broom at the top, and how the needles are a brighter green, softer, more multitudinous than the kotobuki base material.
Here is a good article with images.
An example for bonsai is the JBP cultivar Pinus thunbergii "Kotobuki Yatsubusa". All yatsubusa JBP came from a witch's broom on a kotobuki. Here is a photo of the mother plant:
You can see the yatsubusa witch's broom at the top, and how the needles are a brighter green, softer, more multitudinous than the kotobuki base material.
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Bonsai Nut
Nuttier than your average Nut
Depends on what caused the witch's broom. If it were aphids, for example, removing the aphids would cause the tree to revert to its normal growth habit. Only witches' brooms with genetic cause can be propagated with a hope of retaining the same genetic characteristics. You wouldn't try to remove the entire broom - rather take a cutting or make a graft from a piece of it.
just.wing.it
Deadwood Head
Is Dwarf Alberta Spruce from a Witch's Broom?
This year I've been noticing many landscape DAS's that appear to be reverting to normal growth?
How common is this?
What causes it?
Is it similar to a variegated plant reverting to straight green leaves?
This year I've been noticing many landscape DAS's that appear to be reverting to normal growth?
How common is this?
What causes it?
Is it similar to a variegated plant reverting to straight green leaves?
Melospiza
Shohin
I think many cultivars have the capacity to revert to the straight species. I have seen dwarf spruces revert to normal growth, variegated privet revert to normal, green-leaved privet, weeping cherries revert to upright growth.
When a variegated/dwarf/weeping/fancy-leaved cultivar produces a "normal" branch, that branch is usually more vigorous than the cultivar, i.e., it grows quicker, photosynthesizes better, survives cold and drought more easily etc. This makes sense because the fittest version of the plant is what would survive in the wild. This eventually results in the reverted branch taking over the whole plant, with the 'fancy' part of the plant dying off.
Another interesting effect I have seen in parks is with cultivars grafted on more hardy and vigorous rootstock, chiefly cherries. If the gardener neglects to remove rootsprouts or shoots growing from the stock, they end up taking over the whole tree and the more interesting part of the plant dies off.
Melospiza
Shohin
'Reversion' is simply the cultivar mutating back to its original form, so it applies to cultivars grown from cuttings as well as the part of grafted plants (scion) above the graft union. I have seen some fancy-leaved Japanese maples reverting partly to a more plain form.
Melospiza
Shohin
It's not something that happens often, and some species are more prone to it than others. If it does happen, you can always cut off the reverting branches. It's really not something a bonsaiist has to worry about.
Bonsai Nut
Nuttier than your average Nut
Here's an extreme example of what @Melospiza is talking about. I have a variegate Chinese elm that I am growing out to increase the trunk caliper. This summer, it was almost completely defoliated by a tree rat - a very discriminating tree rat that only liked the small leaves. The rat kept returning each night despite my best efforts to prevent it, even crawling under a net that I had placed over the tree. Eventually I moved the tree to the other side of my yard, where it has started to recover.
Because the tree rat left the larger leaves alone, I have left them on the tree as well in order to provide energy to the tree as it recovers. I now have three different leaf sizes on the same tree; small, medium and large. In the spring when it pushes new growth I will remove the large and medium branches and it will be back to being 100% small leaves.
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Leo in N E Illinois
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I can not speak for the actual history of the cultivar ''Dwarf Alberta Spruce'', I don't know when or where it was found. There were 5 or more possible causes for witches brooms. Disease and chemicals being 2. Random probability is another. Many witches brooms disappear after you clean up the cause. Treat for downy mildew, the tree reverts back to normal.
There are 2 changes that cause relatively stable witches brooms, that can be stable long enough to be propagated.
Epigenetic changes - this is activating or deactivating the protective proteins that allow or prevent a segment of DNA from being read. Your skin cells and heart cells and brain cells all have the same DNA coding. There are proteins that block the reading of large parts of the DNA for each tissue type, this way the heart muscle cells only read the parts that tell it how to be a heart muscle cell, not the directions on how to be a nerve cell. Similarly the skin cell has proteins blocking the reading of directions for becoming a heart cell. This blocking and unblocking of the DNA Is called Epigenetic Control. Many witches brooms are screw ups in this mechanism. If the DNA at a specific location becomes methylated, the blocking control protein becomes semi-permanently bound to that portion of DNA. If it happens in the right spot, it creates what looks like a true genetic mutation, and can create dwarfs, contorted growth, variegated leaves, new flower color patterns, and all manner of other horticultural oddities. This methylation process can be quite permanent, hand even be inherited through seed propagation. BUT the methylation can reverse itself. Where it does you get the ''reversion'' to normal growth. As described above. So the underlying DNA still has all the code for the normal form of the species, so when the epigenetic control is unblocked, the growth reverts to normal. Some epigenetic changes in trees (and in humans) are known to persist through 2 or 3 generations.
A second genetic form of mutation which forms a stable witches broom is an actual point mutation in the DNA. This is where the DNA has changed, and it will never, or almost never change back. This is not as common as the epigenetic change, but when it happens it will be stable for thousands of years, and it will be heritable through thousands of generations.
It is hard to tell epigenetic changes from genetic mutations, it takes time and lengthy testing to sort out which is which. So it is very seldom that it is really known which witches broom originated from which type of change.
The Dwarf Alberta Spruce reverting to normal fairly regularly is likely a good indicator the original witches broom is from an epigenetic change, the underlying DNA of the Dwarf Alberta Spruce is still for the normal White spruce or normal Alberta spruce. Since the DAS is a far northern tree, mostly occurring north of the Canadian border, it is very likely that heat stress is contributing to the reversions.
There are 2 changes that cause relatively stable witches brooms, that can be stable long enough to be propagated.
Epigenetic changes - this is activating or deactivating the protective proteins that allow or prevent a segment of DNA from being read. Your skin cells and heart cells and brain cells all have the same DNA coding. There are proteins that block the reading of large parts of the DNA for each tissue type, this way the heart muscle cells only read the parts that tell it how to be a heart muscle cell, not the directions on how to be a nerve cell. Similarly the skin cell has proteins blocking the reading of directions for becoming a heart cell. This blocking and unblocking of the DNA Is called Epigenetic Control. Many witches brooms are screw ups in this mechanism. If the DNA at a specific location becomes methylated, the blocking control protein becomes semi-permanently bound to that portion of DNA. If it happens in the right spot, it creates what looks like a true genetic mutation, and can create dwarfs, contorted growth, variegated leaves, new flower color patterns, and all manner of other horticultural oddities. This methylation process can be quite permanent, hand even be inherited through seed propagation. BUT the methylation can reverse itself. Where it does you get the ''reversion'' to normal growth. As described above. So the underlying DNA still has all the code for the normal form of the species, so when the epigenetic control is unblocked, the growth reverts to normal. Some epigenetic changes in trees (and in humans) are known to persist through 2 or 3 generations.
A second genetic form of mutation which forms a stable witches broom is an actual point mutation in the DNA. This is where the DNA has changed, and it will never, or almost never change back. This is not as common as the epigenetic change, but when it happens it will be stable for thousands of years, and it will be heritable through thousands of generations.
It is hard to tell epigenetic changes from genetic mutations, it takes time and lengthy testing to sort out which is which. So it is very seldom that it is really known which witches broom originated from which type of change.
The Dwarf Alberta Spruce reverting to normal fairly regularly is likely a good indicator the original witches broom is from an epigenetic change, the underlying DNA of the Dwarf Alberta Spruce is still for the normal White spruce or normal Alberta spruce. Since the DAS is a far northern tree, mostly occurring north of the Canadian border, it is very likely that heat stress is contributing to the reversions.
Leo in N E Illinois
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@Peter44
Japanese Maples (JM) - everything about witches brooms in conifers, ''mostly applies'' to Japanese maples. Except - Japanese maples, when young, will often revert to juvenile foliage. This is a process like Junipers having needle like foliage when juvenile, and scale like foliage when mature. The juvenile foliage of a Japanese maple looks pretty much like ''normal'' foliage of a ''normal'' Japanese maple. Once the JM's growth rate slows down, the foliage will revert to the ''adult'' or mature foliage. JM with finely cut leaves, will often have normal leaves until the branches are over 3 to 5 years old. For some JM, the variegation pattern won't appear until growth as slowed down, and the tree has some ramification. So for most of the JM being propagated out there, you have this confusing couple of years where the tree looks like you paid extra for an ordinary JM, but then once the tree settles down, the ''adult traits'' should appear.
It all gets a bit confusing, but I would not worry, I would still pick up named varieties of JM raised from cuttings so you don't have to deal with graft union scar issues. If Brent is selling a JM cutting of a named cultivar, you can be fairly certain it is a stable mutation, and even though you have a few years of ''normal'' green foliage, it will switch over to the mature foliage as described in his catalog.
Japanese Maples (JM) - everything about witches brooms in conifers, ''mostly applies'' to Japanese maples. Except - Japanese maples, when young, will often revert to juvenile foliage. This is a process like Junipers having needle like foliage when juvenile, and scale like foliage when mature. The juvenile foliage of a Japanese maple looks pretty much like ''normal'' foliage of a ''normal'' Japanese maple. Once the JM's growth rate slows down, the foliage will revert to the ''adult'' or mature foliage. JM with finely cut leaves, will often have normal leaves until the branches are over 3 to 5 years old. For some JM, the variegation pattern won't appear until growth as slowed down, and the tree has some ramification. So for most of the JM being propagated out there, you have this confusing couple of years where the tree looks like you paid extra for an ordinary JM, but then once the tree settles down, the ''adult traits'' should appear.
It all gets a bit confusing, but I would not worry, I would still pick up named varieties of JM raised from cuttings so you don't have to deal with graft union scar issues. If Brent is selling a JM cutting of a named cultivar, you can be fairly certain it is a stable mutation, and even though you have a few years of ''normal'' green foliage, it will switch over to the mature foliage as described in his catalog.
just.wing.it
Deadwood Head
Thanks @Leo in N E Illinois
I was also wondering if anyone knows about Shishigashira?
Is that from a witches broom?
I was also wondering if anyone knows about Shishigashira?
Is that from a witches broom?
Melospiza
Shohin
Does not look like a Witches broom to me. Not all congested/dwarf cultivars are witches brooms.
Leo in N E Illinois
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Honestly I don't know. If you can find a copy of Vertre's Maple book, it might have answers. Or contact Buchholz, he tends to know this stuff. Buchholz owns a wholesale only nursery, and writes a really nice blog on landscape trees.
Flora Wonder Blog, by Buchholz.
http://florawonder.blogspot.com/
Flora Wonder Blog, by Buchholz.
http://florawonder.blogspot.com/
Vance Wood
Lord Mugo
I have Vertrees book on Japanese Maples and I do not recall mention of witches brooms. Most J. Maples are the product of cuttings or grafting and the soures are generally created from identifying unique seedlings and grafting subsequent progeny.
Orion_metalhead
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