Kathryn (k8tpayaso) has potted rootstock (a lot of potted rootstock). I had forwarded a response to her that I had received (some time ago) to her about grafting to bare rooted mulberry rootstock (bleeding rootstocks). All her rootstock has been potted up already…Do you think it is best to pull them up now or just graft to the potted rootstock?
OK…this is the answer I received from Dithmar (a Belgium nurseryman) as to his opinion why some mulberry grafts don’t take. Some of it was a little hard for me to accept and seems to go against standard practice but he has vastly more grafting experience than I, so I should humbly accept:
"I presume we are talking about container grown rootstock.
There are always a good number of grafts that will fail…
Ideally you should use 2 year old field grown rootstock. After lifting the dormant rootstock all the fine roots must washed clean of dirt and cut back until you are left with just the basic root structure. The stem is cut off at about 15 -20cm above the root collar and grafted with the desired variety (cleft graft). The rootstock is potted. It is best to keep the grafted mulberry relatively cool for the first few weeks. When you see the buds of the graft swelling it does not mean that the graft has taken! Normally some wild growth will start to form on the rootstock…just let it grow and cut it back a bit if it grows to fast. Normally the buds on the graft will also start to break open but soon growth of the graft will probably stop.
The reason for this is the strong sapflow of the rootstock that will eject the graft and prevent it from forming callus. This is the reason why it is best to use rootstock with trimmed roots…to reduce the sapflow…and leaving wild growth on the rootstock will make it possible for the rootstock to evaporate and photosynthesize and alleviate the pressure of the sapflow. All of this is necessary to keep the graft alive. Normally the graft should stay green after bud break but it doesn’t leaf out or it shows only some stunted growth. The idea is to keep it in that state until enough callus has formed. When callus has finally formed between graft and rootstock you can trim off the wild growth of the rootstock and as a result the graft should soon leaf out and grow vigorously. Cutting off the wild growth is done after about 5 to 6 weeks.
Of course when the weather turns hot to soon this will not help the healing of the graft because it will induce stronger sapflow which will eject the graft while at the same time the graft will also more easily dessicate.
At this time we are experiencing a short heat wave which is very unusual for this time of the year. Normally we should have about 13-15°C but this past week temps have been 26-29°C. I’m telling you this because I’m also expecting quite a lot of failed grafts due to sudden heat…
When grafting mulberries in the field you should use the same grafting technique and also let the wild growth form on the rootstock until it is no longer necessary…
Another important factor in grafting mulberries is the variety. Some varieties will graft very easily while others are almost impossible to graft. Most often this has to do with callus formation and it is just a fact that some will easily form callus and others will not. These are the same mulberries that will easily root or almost not root at all…"
There’s no one right or wrong way to slow the sap. This guy makes a lot of valid points; also some of which I had never heard prior.
You have to slow the sap flow. You can also drill holes a few inches above the root flare in addition to cutting off the rootstock. Both will allow flowing of the sap prior to grafting. And you can do a third thing and slice into the rootstock with your knife. And when it comes time to graft you can check if the sap has slowed enough by making a few fresh slices and waiting a few minutes to see if bleeds or not.
huh…my approach with mulberries was to mitigate sap issues by “hurrying the F up” in my grafting, and it did pretty OK, but the cut below the graft area I like a lot
I unpotted a couple this morning. Now, washing the dirt out of rootbound potted plants is not my favorite thing. I might drill the holes next.
However it did give me a feeling of accomplishment in unraveling the roots but that was negated by trimming the fine roots. I have a really hard time with that. I went from this
I’ll have to watch that video when I have time.
I’ve utilized a ‘sap-stopper’ modification of a simple bark graft for pecans/walnuts - rather than completely beheading the rootstock, I just cut ~ 3/4 of the way through and break the top over, leaving it attached and ‘hanging’, to act as a sap-drawer. After the scion breaks bud and begins growing, you can just snip off the hanging top.
Fred Blankenship taught me, decades ago, that when doing a banana-type graft, to make a couple of near-full circumferential knife cuts around the rootstock stem below the graft to allow bleeding there - and it may also be that those ‘girdling’ cuts help to concentrate auxins in the portion above them, to help facilitate callusing.
I’ve also seen recommendations to behead the rootstock and wait until bleeding stops - may take several days - then refresh the beheading cut and graft away!
I’ve left some of the rootstock growth and these are growing strong even with that growth. I have started removing a bit of this rootstock growth a little at a time. I have not seen any leaking sap from these grafts. I have grafted several more a few days later that I just made cuts below the grafts. Several of these did leak sap from under the graft taping. Most of the other grafts have green buds but are far behind these. They were done nearly a week later though. So far these two that were root trimmed are doing well and the rootstock growth on the trimmed roots has been very vigorous.
that is a nice study @k8tpayaso. Have to admit though that i never was a fan of root trimming. Partly due to the arid climate where am at.
But for the most part, i reason that the roots store the most energy(proteins and sugars from previous year’s photosynthesis), and during spring when buds or grafts leaf out is when the food supply actually goes from the roots to the buds. I mean, the initial growth of leaves and stems in spring is totally dependent on stored food from last year’s photosynthesis(an initial net loss of proteins and sugars occurs to produce the solar panels–leaves) and will take a while until a good amount of foliage has unfurled to resume photosynthesis and replenish what the roots have lost.
it is also hard for me to accept what was elaborated on. I actually think that strong sapflow is what grafts need to grow vegetatively and to callus. I guess the closest thing to explain my take on this would be maple trees. Maple trees that are not tapped will leaf out much better than those that are tapped. And those maple trees that are severely bled of sap(relative to size of tree) may result in poor growth and possibly death. The other evidence that can be reproduced empirically would be bark-grafts vs. same caliper grafts. Bark grafts are less likely to be runty compared to same-caliper grafts, because what was originally meant to subserve a great number of buds is now tasked to supply sap to just a few buds on the graft/s.
also not sure how sapflow can be so strong as to eject a graft.
Last year I had bud growth on almost all of my mulberry grafts and out of about 12 I only had one that lived to grow. When I took them apart they we full of dry crusty sap and no callous had formed. I think if the graft line fills up with sap it keeps callus from forming. I know sap has to flow through to feed the graft but when it ooozes out the cuts it’s just overwhelming…and ugly. Lol. These are rootbound potted rootstocks that are being reduced to small grafted shoots so I thought I would try it since hardly anything took last year. It sure looks like it is working. But yes, cutting those roots off made me wince…
My understanding is suppressing or restricting the sap delays the scion from growing before the scion and rootstock junction has calloused over…But I seem to get most of my graft failures when the scion fails to bud out at all, not when it is pushed out too fast!..So yeah, I don’t really get it…but I’m also the last person in the room to get a joke…so what does that tell you…
Many plants such as grapes are like this they flood the graft and the graft fails. Grapes always get an extra cut to bleed the sap off. The mulberry i grafted either i fail or not so i suspect it is about timing and sap flow.
maybe it is just me, and here i go again with my admittedly radical and never-heard-of rationales…
anyway, to explain how i understand this, probably best to use easy-to-root and water-logging-tolerant species as jasmine(jasminum sambac) as a hypothetical study. If we place a jasmine stem in a big transparent bag with moist air, it has a good chance of producing callus at the base, root, and leaf out. It will survive for a few weeks. If we place it in a vase with water, it will do the same, but will grow more vigorously and longer lasting compared to the one in the bag. But if get a stem and if we decapitate a huge jasminum rootstock with healthy roots, and bark-graft it as the sole budwood , it will be the most vigorous of all and least likely to fail.
with regards to restricting growth before callusing, i actually think that callusing need not precede leafing out for the graft to be successful. Phloem is what we severe when we remove budwood and graft to a rootstock or whenever we girdle trees, xylem(sapwood) may be physically severed but will not stop upward movement of sap from the rootstock, but phloem has to be re-established from cambium before the rootstock gets channeled products of photosynthesis.
in effect, girdling actually temporarily benefits the foliage and stems above it, as the food supply from photosynthesis is held back, which is what some juju aficionados here are doing to coax laggard cultivars to bear fruits.
thus said, i actually consider an upwelling of sap being extremely desirable, as it is the best tissue-culture-reagent a callus can have. Much better than plain water or ambient humidity, and abundant sap is better compared to limited sap( as in my tapped vs. untapped maple trees analogy).
if there might be reasons why grafts fail, i actually find it likely to be due to low-sap flow. Or to other reasons other than abundant sap.
Figs are another plant that bleeds when cut. I’ve had grafts flood, leak sap from the graft union, and fail to take. But that has never happened if the rootstock has lots of foliage to allow the sap a good place to go. If all the foliage is cut off the graft will bleed and fail. T buds done in summer with high water use have never failed due to flooding. There is lots of foliage above the bud insertion point. This spring W&T type grafts bleed and failed if all the top/foliage was cut off prior to placing the scion. If the plant had other shoots with foliage then no bleeding and graft took.
I find cuts thru the bark or even cuts half way thru the stem don’t bleed enough to help.
Raf…Are you suggesting that Katy and I are anything less than perfect on our technique?
But I’ll go along with the "other reasons’ notion…Some of the grafts I considered to be perfect failed, while poorly done grafts grew…go figure! I suspect that there are many factors which influence grafting success…weather, compatibility, timing, phase of the moon, etc.
forgot to say, sap can gum up when exposed to air/debris, and that is definitely a no-no, much like blood is rendered useless(apart from actually causing a blockage), when it coagulates after being exposed to certain substances.
but in a totally closed system, a great amount of fluid, functional sap is what’s needed for any cambium callus, because the upwelling of nutrition from rootstock is what sustains the initial growth of buds, as there is zero photosynthesis if foliage have yet to unfurl.
not more imperfect than mine It is just that some nodes are inherently shot(difficult if not impossible to tell the good node from the bad node), and/or plenty debris/gummed sap got stuck at the xylem interface. Also, the sheer act of cutting stems is outright contamination with microbes/fungal spores, etc, which may compromise or spell death to the budwood, or even the rootstock/interstem
I see sap flow from a different perspective. If your theory were true plants that bleed would be easy to graft. That’s not the case. In fact from my experience it’s quite the opposite. Can you actually name a plant that bleeds a lot that’s easy to graft? The biggest bleeder I know of is grapes. It’s very difficult to graft.
Sap flow isn’t needed for callus formation. Pears and apples don’t bleed when cut and are the easiest fruits to graft because they form lots of callus to fill in any gaps in the union. Grapes form a lot of callus when rooting them as cuttings. There is no sap flow in a cutting that is in a rooting bed. So callus doesn’t form from nutrients in the sap. It’s formed from carbohydrates and water in the wood.
It is just that some nodes are inherently shot(difficult if not impossible to tell the good node from the bad node), and/or plenty debris/gummed sap got stuck at the xylem interface. Also, the sheer act of cutting stems is outright contamination with microbes/fungal spores, etc, which may compromise or spell death to the budwood, or even the rootstock/interstem