A broom are a very little part of the tree, received a very little part of heat, when grafted, he became a "tree" itself, with all the heat furnished by the roots.
AND the roots are not a broom but a normal roots !
By this way the scion are influenced by the roots.
About the needles, it's neccesary to clean the plant, the compact branchs system remains many needles with sometime some fungi.Clean your broom for air circulation.
Clement

sorry clement.. let me be a little clearer...

i meant while they are still attached to momma.. hanging way up in the sky ...

asking the question from the other end of the spectrum.. what causes brooms .. and is that why they look so sickly on the tree ???

i suppose.. in other words.. is disease one of the factors that can cause a broom ...

ken

Yes, a lot of brooms are caused by disease (mostly not transmissible diseases, but some are).

Some of the dead patches are also caused by the density of the broom making it impossible for normal needle drop of old dead needles to occur, so old dead foliage accumulates and blocks light and ventilation from the live foliage - good idea to clean out broom dwarfs regularly so they don't get clogged up.

All this is a large part of why I don't like these dwarf broom cultivars ;-)

Resin

so once they are harvested and grafted.. the disease issue is mostly resolved???

what diseases can cause a growth mutation?? [if those are the right terms]

makes sense on the topical needle problems.. with lack of proper air movement.. etc ... but that didnt cause the broom ...

is it something akin to a cell cancer causing weird growth on a bud ?????

give me some words of art .. but dont get too complicated... lol ...

ken

Interesting topic. Arceuthobium is one disease that can cause deformed growth, including brooms.

When I first started broom hunting, I was excited to find a lot of brooms, but was later told that many of those brooms and unusual forms were due to arceuthobium, and not good for grafting. Better to find non-diseased mutations.

My guess is that a diseased scion, if grafted onto healthy rootstock, would either remain infected or become healthy. If it became healthy, it might revert to normal growth (e.g. not dwarfed, etc.).

I have found a few brooms that were healthly-looking all over, but then there are others that do seem to suffer in certain portions from lack of light, air flow, etc. as mentioned above.

Is there a master list of what causes each mutation?

I believe metasequoia Ogon arose from an irradiated seed.

Lightening strikes and simple bud-mutations are two other reasons they form.

Dax

Disease or parasite attack might trigger a counter-attack by the plant in the form of an unusually large amount of growth-hormones being produced,resulting in abnormally high bud proliferation ...but then,what causes dwarf-ism ??? (Just my 2 Euro-cents, whilst they're still valid! ) T.

It's geared into DNA of all living species is the simplest answer I come up with. I recall a long time ago a girl on a conifer forum whom worked in forestry came upon a grove of pygmy Pinus ponderosa. That illustrates extreme levels of dwarfism of which I am curious to know the reason(s) of that level of occurrence.

Dax