[NAFEX] bark damage-- recap.
breen at fedcoseeds.com
Sat Dec 10 22:50:57 EST 2005
yep, easy trick from arboriculture class:
xy-up! (xylem=zy-lem phoneticly)
Most woody plants can heal a wound down to but not through the cambium, as long as
the cambium does not get scorched by excess heat/light. Luckily most girdling
occurs during our colder spells here in Maine. The cambium will readily build new
phloem, but the level of stress that the tree endures has much to do with th epoint
in its yearly cycle in which the wound occurs. During and immediately after
flowering and first leaf are bad times for wounds of any type, as well as September
through November. Cambium is so incredibly thin that most people actually are
lining their grafts up with the two phloems matching, not the cambial layers. This
works pretty good, but can be the source of problems in mismatched rootstock/scion
sizes for whipping, and cleft grafting. Beginning clefters, especially on branch
topworking, can see what they have been told is a simple graft turn into a no-take.
This is because the phloem of the branch stem is many times thicker than the scion,
and engulfes the cambium of the scion. This is one of the reason folks report poor
attachment for cleft type grafts. The scion can leaf out, but has not had
cambial "bonding". The scion cambium can and often does grow back toward the branch
cambial layer, but until they meet the growing scion is in danger of wind, bird,
and death from poor alignment.
Finding the cambium:
With a sharp knife, shave through the bark into the white ( can be other colors
depending on species)layer below: this is the phloem. Then carefully shave through
almost parallel down into the wood (xylem and obviously wood-light yellow white and
hard. Between the white phloem layer and the wood layer, a very thin green or grey
or tan (and many other colors depending on the species) is visible, sometimes
barely so. Here is your target. And everything your tree depends on.
zone 4, Maine
On Sat Dec 10 16:01 , 'tanis cuff' <tanistanis at hotmail.com> sent:
>I just ran thru the string on girdling, and had to go review what is phloem
>vs zylem, and wanted to clarify where in the plant the roots deliver up, and
>where the leaves deliver down.
>One of the postings I think said the roots deliver via the thin growth layer
>just under the bark. That's incorrect. The roots deliver (water &
>minerals) via the tiny tubes in the interior or wood part of a trunk or
>branch. The leaves deliver carbs & such to the roots via the thin layer
>very close to the bark. (The inner tubes are the xylem, the outer is the
>phloem. And if I understand correctly, the famous 'cambial layer' is
>between the 2 and produces new cells for both.) This is why when a tree is
>girdled, it looks OK for a while: roots can still deliver juice to the
>leaves; but the tree will eventually fail because leaves are not delivering
>food to the roots. Unless it can throw a water sprout from below the
>girdle, or root suckers, either/both will then connect leaves with the roots
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