Curious..... I just ran a search for "broom" (as in Witch's Broom) on this forum, and got nothing. Would anyone have any knowledge of Araucaria brooms having been found somewhere ? ....any details ? There were some inquiries about bonsai Araucarias, with only poor results cited in the replies. It seems to me that WB's would be much better suited for that purpose -- besides being of interest by themselves. Of particular interest to Canadian subscribers to this forum would be WB's of tropical Araucarias, as these would be easier to move indoors during winter. Thanks in advance for any replies.
I've never heard of, nor seen, a WB on an Araucaria. Strikes me as somehow a rather improbable possibility, too - I even wonder if their very stereotyped branching structure might make them impossible.
Curious, I too, have not heard of this term when referring to Araucaria. You can "growth restrict" these Araucaria, to a certain extent, by limiting the container size, using bonsai soil, and some limited root trimming. However, they like a rather tall, narrow container (rather than a traditional shallow bonsai pot) due to the tendency to drop a deep tap root for stability. In addition, the branches are not suitable for "pinching off" like most conifers used for bonsai. Having said all that, some of the Agathis species (Araucaria cousins), when mature, do appear to have a "broom-like" top growth. They shoot up through the canopy of the forest and then spread out their foliage. Their growth pattern appears better suited for bonsai techniques as they have a more leaf-like foliage and freely branch. I have some small Agathis and Araucaria trees that I use as "patio plants" when the weather is warm, and seem to do well in the winter, indoors, near a window.
Thanks for the photo -- the Agathis ovata does resemble an Araucaria muelleri superficially. Oddly enough, the other Agathis species don't resemble Araucarias at all. Do Agathis develop witch's brooms ?
I think we are having a difficult time understanding what is meant by a "witch's broom". What, exactly, are you referring to as I've never heard the term used in the description of Araucaria. Do you have a photo or web link that you could attach?
Many dwarf and miniature cultivariants of conifer and other species are derived from witch's brooms, which form randomly on a few full-size trees. The brooms are harvested and propagated by grafting on a young plant of the same or similar species. See for example Jan Slama's WB web site, wbgarden.com, in particular this page: http://wbgarden.com/nove/sb/indexen.htm
Jaro, I've learned something today. I've never seen or heard of these "witch's brooms". Very interesting. I'll have to keep an eye out for them the next time I go hiking around in a forest. Daniel, Sorry about the images. I thought if I simply gave the website credit for the image, it would be alright. My mistake.
No problem, Mark. Sometimes credit is enough, but only if the organization / person allows it to be. Image use is a bit of a grey area when it comes to educational purposes and international usage / distribution, actually, so I opt for the most conservative approach.
Jaro, From a rather limited web search, these witch's brooms appear to be stimulated by some types fungal infections, rather than a random anomolous growth pattern. I found various sites, pdf files, etc. with descriptions of witch's brooms on other trees than Araucariaceae (various conifers, ginko, maples, etc.). It is difficult to say, but are Araucariaceae immune to these infections, is it deadly, or simply so rare as to not be described in the available literature? An interesting thought, though, would be to examine the specific growth factors involved with this growth pattern, as triggered by the specific fungi under controlled conditions. Perhaps, a new method of rapid propagation could be found and used. If there were only a plant research center available.... ; )
Most of the witches brooms I am familiar with are caused by mistletoes, which as far as I know are fairly host-specific.
I have read somewhere that the Araucaria produce copious amounts of resin, which would inhibit the formation of a witches broom as well... I would think.
I suspect a more important point is the different growth strategies between Araucaria and other conifers. Most conifers produce side branches at pre-determined times (usually intervals of one year); thus a disease (fungus, mistletoe, whatever) that reduces growth rates also reduces the spacing between branches. Conversely, branching in Araucaria is not time-related, they do not produce one whorl of new branches on the trunk each year, but more when a set length of stem growth since the last whorl has occurred. A disease which slows down the growth rate would not then affect the spacing between the branches, all that would happen with the slower growth is that new branches would be produced less frequently.
http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2000000300013&lng=en&nrm=iso I hope this link works. It is a scientific article describing what Michael said regarding how juvenile Araucaria grow with respect to height, frequency of branching, etc. under different light conditions. I may have found a way to keep my trees shorter and more compact.
I don't see how spacing between branches is relevant to the formation of witch's brooms -- typically, wb's occur on a branch, not on the tree trunk.....
I will just endorse Michael's observation. I have seen plenty of Araucaria and Agathis trees, in the wild as well as in cultivation, and never saw the faintest suggestion of a witch's broom.
Hi Jaro, WBs can occur anywhere on a Pinaceae plant, infection isn't limited to side branches. Of course if a lead shoot on a pine or spruce is infected, an uninfected, stronger-growing side shoot will take over and become a new leader. Also what applies to the whorls of branches on the trunk of an Araucaria, applies just as much to the branchlets on a branch of an Araucaria; their spacing does not relate to time.
