I was sluggish to answer an English plantsman's email from a few weeks ago. He asked,
Some time ago in one of your blogs you mentioned grafting Disanthus using Parrotia as the rootstock. Have you investigated further and does it make a permanent combination? I find on its own roots it is a BBBB! to grow well. It grows magnificently well in the gardens along the coastal strip of Western Scotland - Inverewe etc.
Finally I responded:
I intended to answer your question about Disanthus in a blog but it never happened.
I once had extra Parrotia rootstock so I grafted whatever I could think of onto it. I must have done about 20 Disanthus and 4 lived. These were potted up and kept a full year, then planted out. All 4 were dead the next spring. I blamed the cold winter but who knows? A few years ago I grafted 10 'Ena nishiki', the variegated Disanthus, and got 0 percent. My one stock plant – on its own roots – died this past winter so I don't even have a single Disanthus on the place.
Hamamelis intermedia 'Arnold Promise'
Hamamelis and Parrotia seem to be a good match, and the advantage of grafting a dwarf or slower cultivar on a standard is that it eventually gives you attractive bark. About 6 or 7 grafts of 'Arnold Promise' were done on a larger branched Parrotia many years ago. All took and today the graft unions are not evident, except to me since I know about them. The trunk is spectacular and I like to point out to plant know-it-alls – who nod in approval – how wonderful it is to have colorful, exfoliating bark on witch hazels...then they look a little confused.
Fothergilla monticola with Parrotia persica trunk
4 Fothergilla monticola were grafted on a Parrotia standard 30 years ago, and again, great bark. The scions on each branch began fall color a few days apart, and so their colors were initially different and I found that amusing. Eventually they all turned the same glowing orange. A couple of years ago one branch died for unknown reason so I pruned it out. But every time I walked past the tree the hole in its canopy bothered me, so a year later I cut the whole thing down. Was it delayed incompatibility? I don't know.
Fothergilla 'Mt. Airy' on Parrotia standards
We used to field grow Fothergilla 'Mt. Airy' on 5-6' standards – a double graft on a single whip. The graft unions were always evident in winter*, but that didn't stop customers from ordering them in summer. Two older specimens remain in the garden. They look fine at about 20 years of age. We've also succeeded with Sycoparrotia as rootstock.
*The 'Mt. Airy' trunk is smaller in caliper than the rootstock.
We don't do any of these Parrotia standards any more, maybe because I've grown old and boring. I'd like to see a younger nurseryman give a go with the Disanthus at least, because it is impossible on its own roots at Buchholz Nursery. Don't you think that if these intergeneric grafts were commercially feasible the Dutch would have figured it out a hundred years ago?
I wish I could give you a more positive report.
Finally answering him prompted me to incorporate my reply into a blog after all. Least Mr. B.H. or others assume that I am a grafting wizard, I know that I can make a living at it but I'm not really such an expert. The fact is: I personally haven't grafted a single stick in the last twenty years. I cut all of the scions now – about 40,000 per year – and my ace grafter Juana, whom I've bragged about before, achieves a high rate of success. And yes, she got her deserved pay raise. Since she's so good and precise at everything she does I think it's time to pass some of the scion cutting on to her as well.
Selecting the best (or correct) scionwood is extremely important – more important than the physical act of connecting the two parts together, which virtually anyone can do. Knowing what to graft onto what is a more elevated matter. You learn by copying others, of course. You either bluntly confront a successful nurseryman about what rootstock to use for the scions you wish to graft, or...more likely, you glance at him sideways to see what he is doing while you chat about the weather.
|Picea pungens 'Baby Blue Eyes'|
Sometimes, though, copying others will teach you a lesson about what not to do. I once worked for a nurseryman – err...actually not a nurseryman, but rather a nursery owner – who insisted that the best scion-to-rootstock policy was to graft your scion choice onto the same species of rootstock, always. So for blue Picea pungens cultivars we grafted onto Picea pungens rootstock exclusively. I was starting my nursery at the same time and I chose the more vigorous Picea abies for my own grafts. By coincidence we both bought 2-0 (meaning two-year) bareroot seedlings from the same grower – he, the “Colorado spruce” and I, the “Norway spruce.” The P. pungens don't really prosper in Oregon on their own roots; they grow slowly and show great variegation compared to P. abies. Furthermore P. pungens resents being grown in black plastic pots when it turns 100 degrees F, as it does every year. By the following winter my rootstock had twice the caliper and his were thin and feeble; and you really do need a pencil-sized (plus) caliper at least if you want to graft the terminal shoots of the pungens cultivar. In other words, the grafts that “succeeded” on his rootstock would take an extra year to catch up to mine, if not longer. Did I report my conclusions to my nursery employer? No, and the reason was because he was Dutch. “If you're not Dutch, you're not much,” his round-headed blonde son used to say. It turned out that Dutchman's brother was the propagation expert of the two, but he had retired a few years previous. The owner was the owner and not a propagator. His forte was not rootstock-scion details but he was too stubborn to admit it. But, as I alluded to earlier: generally speaking, all hats go off to the Dutch when it comes to plant propagation. They are in such a competitive environment that to be dumb is to fail.
P.S.: I've never met a Picea species that didn't admirably connect with Picea abies.
Chamaecyparis nootkatensis 'Sparkling Arrow'
Is it better to grow Chamaecyparis nootkatensis cultivars on their own roots (hardwood cuttings in summer or winter), or better to graft them on a different rootstock? Either way works, except that when you graft, your rootstock is usually a three-year-old vigorous plant, so your grafts have a head start to mature. And maybe the variegated selections like 'Sparkling Arrow' are more vigorous on borrowed roots. Thuja orientalis is often used for nootkatensis grafts, and very few people in Oregon knew that when I began my nursery. Other growers, instead of buying liners from me, would hear that Thuja was the required rootstock and so they began their grafting program by using Thuja occidentalis 'Pyramidalis' or 'Smaragd'. The grafts would “live” sort of, but never would they copulate (as the Germans say) into a strong union. Give enough time and they all eventually failed.
|Chamaecyparis nootkatensis 'Green Arrow'|
I learned to use Thuja orientalis because a previous employer bought grafts from a New Jersey nursery in the 1970's, yeah from a nurseryman of Dutch descent, and a Thuja orientalis sprouted from beneath one of the grafts. So the secret was out. I bought a Thuja orientalis cultivar for stock plants from which cuttings were made to graft the nootkatensis onto, so young Buchholz produced a few thousand grafts per year and made tons of money. I produced 'Pendula', 'Glauca Pendula' and the first crops in the world of 'Green Arrow'. The former two have fallen out of favor in recent times, while 'Green Arrow' is grown by dozens of companies and 6-8' trees are available inexpensively. I remember a Seattle-area retail nursery was offering them at $29.95 in 2009 at the beginning of the Great Recession. They looked good, and came from a company I never heard of before. So they didn't need to buy my $55.00 wholesale-price trees any more. The fun didn't last long, though, as both the grower and the retailer are no longer in business.
|Chamaecyparis nootkatensis 'Pendula'|
Propagator Nelis Kools from The Netherlands prefers to use seedling nootkatensis as understock, and maybe this practice is widespread in Dutch horticulture now. The theory is that the mature “Alaska cedar” cultivars are less likely to produce (unsightly) seed if grafted onto their own species. It would be interesting to do a side-by-side experiment and observe the outcome every decade. My oldest nootkatensis is 'Pendula' in the Display Garden – on Thuja orientalis – at 44 years of age. While it cones it does not do so excessively, nor unsightly. Also, I've noticed a couple of times that western Oregon growers with flat fields and heavy soils can have more death with their young crops during wet winters and springs when using nootkatensis as rootstock. Naturally that would include cultivars produced from rooted cuttings. I know that the casual gardener doesn't follow most of what I've just said. Scions, rootstocks, cultivars – why does it have to be so complicated?
Well, it's not complicated, yet it is complicated. On the one hand you simply look at the trees, and if one resembles the other perhaps they would be compatible as a graft, and so you try it. On the other hand we have seen that Thuja occidentalis – as rootstock – is not compatible with Chamaecyparis nootkatensis, whereas the related Thuja orientalis is. That doesn't pass the eye test and the poor nurseryman learns the hard way. Even more bizarre is that rootstocks can be cultivar specific. For example: I have found that Chamaecyparis nootkatensis 'Green Arrow' happily copulates with Thuja orientalis, but that Chamaecyparis nootkatensis 'Van den Akker' does not do so well, but experiment for yourself and see. Also, as I have reported in a previous blog, Cupressus cashmeriana is intergenericably compatible with the cultivar Thuja occidentalis 'Smaragd' as rootstock, but much less so with Thuja occidentalis 'Pyramidalis'. Isn't that weird?!
|Kew Gardens front gate|
I once grew a few Sorbus commixta, my favorite rowan of all. I wanted to propagate it even though my customer base didn't know it, or think they should have to pay my price to buy them. But the species is a knockout, and I first encountered it in the fall along the walkway near the main entrance at Kew Gardens in London. Later I saw it at Wisley and elsewhere in England, and I understood that the better English arboreta was enamoured with the Japanese species (nanakamado)*. But I didn't have any Sorbus rootstock, so what could I do? Well, we had rootstock of Crataegus monogyna inermis for the 'Compacta' cultivar, and former English employee P.T. said that the Crataegus “should work” for the Sorbus, because both are in the Rosaceae family. Since he once worked at Hillier Nursery I assumed he knew what he was talking about and I threw my hat in the ring. The grafts took and grew like weeds, and I sold all but kept one in the garden for my own pleasure. One fall an aggressive customer saw it in its autumn splendor and demanded to buy my last tree. I grunted and groaned, but ultimately relented and sold him the tree (2” caliper at $110.00) because I reasoned that I could easily acquire it again. I was wrong, and 15 years have now passed. Last spring I purchased and potted some Sorbus rootstock just in case someone can send me some S. commixta scions – and I would especially love the cultivar 'Embley' with fastigiate branching or 'Serotina' which flowers later in summer. Or...just some seed of S. commixta would please me as well.
*The Japanese name “Nana kamado” literally means nana (seven) and kamado (times in the stove), which describes the firewood's durability, that it doesn't get totally consumed even after repeated use.
Cathaya argyrophylla is an odd conifer, and when it first became available to western conifer aficionados as scionwood, it was suggested that the “holy grail” of Chinese species could perhaps be propagated onto Sciadopitys or Pseudotsuga – or one other genus, I can't remember, but something that didn't look like Cathaya – was it Larix? In any case I finally acquired the plant from seed, and no mean feat as the Chinese claimed to have executed four hapless souls for trying to smuggle out the seed. Geeze – I didn't want it that bad – but when I obtained seed I didn't document my source, and furthermore I labelled my first plants as Sciadopitys verticillata 'xyz' in case any communist thugs knocked at my door. Today Cathaya can be found in various collections, and I don't think anyone need fear execution. We have grown a few from seed – from our own mature trees – and we have rooted a few from rooted cuttings with about a 5% success rate. In the last four years I have grafted onto Pseudotsuga menziesii, and about 90% initially look great. But the jury is still out because some of these “successes” look perfectly compatible for a year or two...then one by one they can turn off-color and expire. Yet, none from two years ago have died. One from four years ago is 4' tall and bushy and everyone wants to buy it. So, I don't know, I've got a couple hundred of these “maybe takes” but I don't think I should sell any yet.
|Larix decidua 'Pendula'|
And what's up with grafting Pseudotsuga onto Larix – or was it Larix onto Pseudotsuga? If one way works shouldn't the other? I first saw the combination – but I forgot what was on what – in Holland at Will Linssen's nursery. He chuckled when we Conifer Society enthusiasts deboarded the bus at his nursery and headed straight to his intergeneric construct. But I remembered the absurdity of these two diverse genera hooked onto each other, and for the heck of it I did it myself. A year later both parts were still alive and I would occasionally point it out to visitors. Now, five years later, the graft is no longer here. Did it finally die? I don't remember...what happened, but it's no longer here.
Don't worry – I'm not making fun of this...grower. I suspect that in a few years he will be enshrined into the Oregon Nursery Hall of Fame by our association, and I know that I'll never be. The point is that there's a lot of ways to hang a graft, and maybe the cosmic energy from the kitchen's microwave actually aids in the procedure.