Procuring scionwood for two grafters keeps our new horticulturist Jordan out of trouble. I go into the field with him and try to explain what is the best kind of wood to cut per each variety...which partially depends on the quality of the available scions, and also how desperate the grafter wants to compromise quality versus the desire for quantity. In other words, we play with the hand that we are dealt. It's hard to put into words what this nurseryman does when I cut scions based upon instinct. Pretty much I sum it up to Jordan: 1) don't believe me totally, 2) try different experiments and keep track of the results, 3) I'm cheering that you'll exceed me as a propagator (that won't be difficult) and 4) hurry up because you're always behind.
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| Dutch Clogs |
So far all of our winter grafts have been put into GH18B where the thermostat is set at 34F, or just above freezing. Sometimes a few grafts in the corners will experience frozen pots for a couple of days – or at least a night – and if we're grafting Picea, Abies or Pinus the graft “takes” wind up being just as successful as those placed in the warmer middle. I often wonder if no heat at all, with considerable cost savings, would yield the same results. It reminds me of the old-school Dutchman where I received training at the beginning of my career: “If you're not Dutch, you're not much” was his thinking, and he tossed some pretty ridiculous theories at me, or at least I proved them so eventually. I did what he wanted at his nursery, then I improved upon it at my place. I've suggested to Jordan that he'll probably look back at his early Buchholz days and make light about the gruff old German and his senseless methods.
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| Cornus kousa 'Summer Fun' |
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| Cornus kousa 'Summer Fun' |
As I write this (2-15-24) the days are considerably longer and its warmer in another propagation house (GH12) where we have cranked the thermostat up to 70F. There are thousands of Acer palmatum and Cornus kousa rootstocks that we are trying to push into growth mode. In addition we have Thuja and Juniperus rootstocks where graft takes seem to improve with extra heat and humidity compared to the Pinaceae at 34F. So, GH12 becomes our “hot house,” and the crew is constantly reminded to keep the doors closed even when all the others are open. Also we must keep an eye on the irrigation due to the high heat. Hurry and worry is how I would sum up all propagation, with every season presenting its unique challenges.
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| Thuja occidentalis 'Smaragd' |
Typically I wait until February to supply high temperatures in GH12, so that the expense of burning fossil fuels is somewhat mitigated by the free energy from the sun. Soon enough we'll be 70F in there without any heater on, and the new owners will be relieved, as they had no idea that a $30,000 propane bill is normal for the winter season. Our first grafts were on Thuja occidentalis 'Smaragd', and included various cultivars of Chamaecyparis obtusa such as 'Melody', 'Nana Lutea', 'Nana Gracilis', 'Vokel's Upright' and others. We also root the above, but the same on Thuja rootstock will result in a more vigorous plant that tolerates less-than-ideal soil conditions compared to cutting grown.
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| Chamaecyparis obtusa on lawsoniana |
While 'Smaragd' is a good rootstock, other Thuja occidentalis cultivars would work just as well for Chamaecyparis obtusa, such as 'Pyramidalis', 'Brobeck Tower' and many others. It's a poor idea to graft the obtusas onto Chamaecyparis lawsoniana, with the above photo demonstrating what can happen. Yes they are “compatible” – more or less – but at advanced age the bole of the understock appears to swallow up the scion, probably which is 'Nana Gracilis'. The curiosity above was photographed at Arboretum Trompenburg in Rotterdam, The Netherlands, one of my favorite plant collections in the world.
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| Cupressus cashmeriana |
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| Cupressus cashmeriana |
Surprisingly, Thuja occidentalis 'Smaragd' makes an excellent rootstock for Cupressus cashmeriana, the beautiful but tender cypress from Bhutan. My theories and practices are based on personal trial and error, with plenty of the latter. There are a lot of similarities with the genera of Thuja, Platycladus, Chamaecyparis, Callitropsis, Calocedrus, Cuprocyparis and Juniperus – all in the Cupressaceae family – and so the propagator can experiment and make his own discoveries and draw his own conclusions. The Cupressus cashmeriana makes a perfectly smooth graft union with 'Smaragd', but cultivars of Cupressus arizonica are not as compatible, at least in my experience. C. arizonica will “take” (poorly) on some of the conifers listed above, with the tops growing fast but the rootstock can't keep up; the evergreen foliage is like a sail in the winter wind and serious staking is required. The most compatible rootstock is C. arizonica itself, but unfortunately it can be hard to locate.
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| Chamaecyparis lawsoniana |
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| Chamaecyparis lawsoniana |
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| Chamaecyparis lawsoniana |
Chamaecyparis lawsoniana is an evergreen conifer from southern Oregon and northern California. Commonly known as the “Port Orford cedar,” the trunks can be impressively silver-gray on mature specimens but I don't find the tops to be particularly attractive. Also it's rather unjust that the specific epithet honored Lawson and Son Nursery in Edinburgh, Scotland, just because Charles Lawson's collectors introduced it into cultivation in 1854. Lawson specialized in grass seed and conifers but just nineteen years later he went bankrupt after an unwise investment in guano from Santo Domingo, now the largest city in the Dominican Republic.
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| Chamaecyparis lawsoniana 'Blue Surprise' |
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| Chamaecyparis lawsoniana 'Imbricata Pendula' |
We use a disease-resistant (DR) rootstock of Lawson cypress developed by the Forestry Department of Oregon State University, and we only graft various C. lawsoniana cultivars on it such as 'Imbricata Pendula', 'Blue Surprise', 'Filip's Golden Tears', 'Pembury Blue' and 'Wissel's Saguaro'.
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| Chamaecyparis lawsoniana 'Wissel's Saguaro' |
Chamaecyparis lawsoniana 'Wissel's Saguaro' is our greatest production number and it forms a nice container plant, but if planted in the garden it will require adequate room for the cactus-like arms to develop. Our oldest specimen in the Display Garden is an architectural wonder, standing about 20 ft (6m) tall with an 8 ft (2.5m) base width. At the beginning of my career in the early 1980s I was gifted a plant of C.l. 'Wisselii' that was grafted onto Chamaecyparis pisifera. The union was obvious at about 6” high and the top significantly outgrew the rootstock, and since it was forever leaning sideways I edited it from the scape at about 15 years of age. 'Wisselii' originated in Tharandt, Germany at a forestry station in about 1885 and was named for F. Van der Wissel, a nurseryman from Epe, The Netherlands. 'Wissel's Saguaro' was discovered as a witch's broom mutation on 'Wisselii' in Holland in 1962 by J. Dekker, but not named or propagated until the 1980s. The cactus form far exceeds its 'Wisselii' parent in popularity and I see them more and more frequently in my Portland-area neighboring landscapes. The C. lawsoniana species is threatened in its native range due to the fungus Phytophthora lateralis, and the cultivar 'Wissel's Saguaro' is apt to be short-lived if irresponsibly produced by nurseries from rooted cuttings. Oregon State continues to develop Lawson cypress for even greater disease resistance in an effort to save the species from disappearance, and we're looking forward to using the improvement as rootstock.
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| Chamaecyparis lawsoniana 'Filip's Golden Tear' |
We have been growing Chamaecyparis lawsoniana 'Filip's Tearful', a very narrow green weeping tree and also 'Filip's Golden Tears', both of seedling origin raised by Dutch nurseryman Edwin Smits. The green selection looks like Callitropsis (syn Xanthocyparis, syn Chamaecyparis) nootkatensis 'Green Arrow', although more narrow – a graceful exclamation point in the landscape. The 'Filip's Golden Tears' is equally as narrow and features soft yellow-green foliage that does not burn in full sun, and it far exceeds the green form in sales, at least for Buchholz Nursery.
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| Chamaecyparis vietnamensis |
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| Chamaecyparis vietnamensis |
I don't care to get involved in the nomenclatural kerfuffle over the recently discovered Callitropsis vietnamensis, the “Vietnam Golden cypress.” We continue to label and place it in the Chamaecyparis genus so as not to confuse our employees, and more importantly our customers. I vowed to continue with the old name until the end of my career, but obviously the new owners (MrMaple) can choose to update the name. Whether grafting the Alaska Yellow cedar or the Vietnamese Yellow cedar, the rootstock we prefer is Thuja orientalis, which now is properly known as Platycladus orientalis. Once again we still use the old understock name rather than re-educating our employees. This is the first year that we have propagated the Vietnam cypress, but our original stock tree was cutting grown. I acquired it as a gift from Steve Hootman, Director of the Rhododendron Species Botanical Garden in Federal Way, Washington, and the photos above are from his impressive specimen at the RSBG.
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| Chamaecyparis nootkatensis 'Green Arrow' |
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| Chamaecyparis nootkatensis 'Green Arrow' |
We grafted 100 Chamaecyparis nootkatensis 'Green Arrow', a Buchholz Nursery introduction from the 1980s, but back when we sold many more conifer liners to other wholesale nurseries we would propagate a couple thousand per year. The selection was originally discovered by the late plantsman Gordon Bentham on government forestry land on Vancouver Island in British Columbia, Canada. It is ubiquitous now, and I frequently pass a planting of about twenty trees used in a median strip on Oregon Hwy 99 on my route between the nursery and my new Portland home.
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| Chamaecyparis nootkatensis 'Sparkling Arrow' |
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| Chamaecyparis nootkatensis 'Sparkling Arrow' |
Chamaecyparis nootkatensis 'Sparkling Arrow' originated as a variegated mutation on C.n. 'Green Arrow' in about 2000 at Buchholz Nursery. One solo shoot produced cream-white markings, about half-and-half with the background of normal green. I grafted it myself and fortunately it “took” – one for one equals 100%, hurray! There is still enough green in the foliage so it can be sited in full sun without much damage. 'Sparkling Arrow' has effectively replaced the old Euro cultivar 'Variegata' because 'Sparkling Arrow's' variegation is more stable, and it also grows with a more narrow form than 'Variegata'.
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| Chamaecyparis nootkatensis 'Glauca Pendula' |
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| Chamaecyparis nootkatensis 'Glauca Pendula' |
The most north row in the Conifer Field of Chamaecyparis nootkatensis 'Glauca Pendula' is probably more of a group designation than a specific cultivar. We propagated and sold liners by the thousands a couple of decades ago because we had a full, pretty good blue-green strain and graft takes were usually very high. It was a money crop for years, but sales dwindled with the economic meltdown in 2007. Apparently some of our customers for 'Glauca Pendula' were the type of growers – usually field operations expanding onto new land with a mortgage – who suddenly found the easy-to-grow trees were difficult to sell. In desperation a lot of their crops were burned or found their way to the box stores for cheap. “Let bygones be bygones” is the new Buchholz management direction, which decided to bring 'Glauca Pendula' back into production. I'm confident that sales will pick up because of the influx of new customers in areas that were previously sparse in sales for Buchholz Nursery.
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| Cupressus macrocarpa 'Greenstead Magnificent' |
Remember, the discussed cultivars of Chamaecyparis vietnamensis, and nootkatensis 'Green Arrow', 'Sparkling Arrow' and 'Glauca Pendula' are all grafted onto Thuja (Platycladus) orientalis. Early in my career I was gifted a wonderful selection of “Monterey cypress,” Cupressus macrocarpa 'Greenstead Magnificent'. It forms a dense spreading evergreen but is poorly named, for “Greenstead” implies green foliage, but instead it is a vibrant steel-blue. As my cutting-grown plant prospered I attempted cuttings myself, but results were near 0%. Hmm...I wondered what would be a suitable rootstock? I could find no information in the literature, but I reasoned that if x Cuprocyparis (syn. Cupressocyparis) leylandii is a hybrid of Chamaecyparis nootkatensis with Cupressus macrocarpa, and since C. nootkatensis is compatible with Thuja orientalis, then probably C. macrocarpa would be as well. And it was so.* Now we produce sizable crops, and a full one-gallon pot can be achieved with just one year of growing past the graft year. Even with a USDA zone 4 rating for Thuja orientalis as rootstock, 'Greenstead Magnificent' is only hardy to 0F (USDA zone 7) so our sales are limited to relatively mild areas like southeast and west-coast North America.
*I found an amusing story about 'Greenstead Magnificent' on the website of one of our customers: “After years of trying to get this plant going, we finally found some stock and bought all they had. This plant is almost impossible to propagate by any method. These grafters must be magicans [sic] to get these plants going. They are so beautiful.” Well, this “magican” just revealed what's behind the curtain!
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| Cupressus macrocarpa 'Greenstead Magnificent' |
Cupressus macrocarpa (syn. Hesperocyparis macrocarpa) 'Greenstead Magnificent' originated as a witch's broom mutation on a tree in the Adelaide Hills, Australia, and I assume the parent tree was also blue. Another theory (Hortiflora) is that it originated as a bud mutation on an old specimen of C.m 'Horizontalis' and introduced by Roger Hall of Newman and Son in south Australia in the 1970s. It seems almost certain that the cultivar name honors Greenstead Nursery, a family operation located in the Tea Tree Gully in the Adelaide Hills that was established in 1985 by Simon and Ingrid Hall.
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| Calocedrus macrolepis |
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| Calocedrus macrolepis |
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| Calocedrus macrolepis |
I feel incumbent to report my grafting failures as well as my successes. Many years ago I acquired a plant of Calocedrus macrolepis that was raised from seed and I was very impressed with its lush blue-green foliage with silver-blue undersides. The rare, upright evergreen is from southern China and northern Myanmar (Burma) but it is only hardy to 10F (USDA zone 8). We rooted cuttings (very easily) for a few years but discontinued due to poor sales based on the hardiness issue. I kept one tree around that was grafted onto Calocedrus decurrens, an experiment to see if I could provide extra hardiness on a USDA zone 5 rootstock. The graft took and the top grew rapidly, but it has floundered recently in Box Area Greenhouse #6, a cold frame with no heat. The graft union is a disaster, an unsightly bulge that constricts top growth eventually. The genus name Calocedrus comes from Greek kalos meaning “beautiful” and cedrus referring to a cedar tree. The specific epithet macrolepis comes from Greek makros for “large” and lepis meaning “scale.” If we were to ever grow the “beautiful cedar” again it will have to be from cuttings or grown from seed, and only offered to customers who are equipped to overwinter.
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| Athrotaxis cupressoides |
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| Athrotaxis cupressoides |
Another attempt at propagation within the Cupressaceae involves the seldom-encountered Athrotaxis cupressoides, the “Pencil pine” endemic to Tasmania. The upright evergreen conifer can live up to 1,000 years and I was impressed with its single-veined leaves which are arranged in spirals, a most skeletal appearance which looks somewhat like a true Cupressus. My original specimen was on its own roots, and indeed we propagated for a few years via cuttings, but after about 15 years in the landscape it perished in a harsh arctic blast. Before it croaked I planned to try propagating on Cupressus arizonica var. glabra, but didn’t have any rootstock at the time. Instead I grafted about ten scions onto Sequoiadendron giganteum because they looked similar, and in fact my Athrotaxis specimen was planted next to Sequoiadendron g. 'Glaucum'. Since the two genera co-existed next to each other in apparent harmony, I supposed they might be predisposed to support each other. One never knows what goes on at night in a tree collection. Seven out of ten Athrotaxis took – at least initially – on the Giant redwood rootstock, but in a fervor of capitalism I sold them all a year later, so I can’t report how they fared in the long run, but I encourage a younger propagator to trial other Cupressaceae rootstocks.
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| Taiwania cryptomerioides |
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| Taiwania cryptomerioides |
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| Taiwania cryptomerioides |
Another intrageneric propagation attempt was to use Cryptomeria japonica 'Yoshino', probably the most hardy of the Japanese cedar’s (sugi) many cultivars, with the scions of Taiwania cryptomerioides. The Taiwania’s specific epithet indicates an affinity with Cryptomeria, and indeed the “Taiwan Coffin cedar” looks like a blue sugi anyway. We used to grow Taiwania from cuttings, just as we do with Cryptomeria, but the Taiwania would initially grow branch-like and require strong stakes for a number of years. My crops looked haphazard and unsalable so I discontinued with it from cuttings; but one stock tree still remained at Flora Farm when I got the notion to use 'Yoshino' as an understock. So far the results look great three years along...with vigorous scion growth that has produced leaders. In its native range of Taiwan, and also a thousand miles away in southwest China, Myanmar and Vietnam, some specimens can grow to over 300 ft. tall (90m), but of course the beautiful genus is threatened by logging. The wood is soft but durable, and spicy scented, so I wouldn't mind to have my coffin made from it (although I'm not in a hurry).
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| Juniperus cedrus |
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| Juniperus pingii |
The final genus I'll discuss in the Cupressaceae family is Juniperus, and for all species and cultivars we use only the understock of Juniperus scopulorum 'Skyrocket' which is hardy and well-adapted for many soils. We graft various “tree” species, such as Juniperus cedrus, the beautiful (but endangered) weeping tree from the Canary Islands, and Juniperus pingii, a Chinese species closely related to Juniperus squamata. These two junipers are seldom encountered, even in comprehensive arboreta, let alone in the horticultural trade, but both are very attractive and plenty hardy at my Oregon nursery.
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| Juniperus deppeana 'Ohmy Blue' |
Another upright tree-juniper is J. deppeana which also thrives on the J. scopulorum rootstock. I suspect that our introduction of 'Ohmy Blue' is J. deppeana var. pachyphlaea due to its white resin spots and alligator-like, checkered bark. The specific epithet deppeana honors Ferdinand Deppe (1795-1861), a German naturalist, explorer and painter. In Latin the name juniperus is derived from junio meaning “young” and parere “to produce,” hence “youth producing” or “evergreen.” Ginepro is Italian for “juniper,” while the grain alcohol gin is flavored with juniper berries. 'Ohmy Blue' was a seedling germinant of the southwest USA-northern Mexico species that I grew early in my career; an admiring visitor exclaimed, “Oh my, that's really blue!” Hence the cultivar name.
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| Juniperus horizontalis 'Golden Wiltonii' |
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| Juniperus conferta 'Blue Lagoon' |
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| Juniperus horizontalis 'Pancake' |
Some of our Juniperus 'Skyrocket' rootstock is about 3' tall, and on those we will top-graft ground hugging cultivars such as J. horizontalis 'Pancake' and 'Golden Wiltoni' and in a few years the foliage will weep down to the ground. Also, the Japanese “Shore juniper,” J. confera 'Blue Lagoon' can be developed into an attractive novelty when grafted high.
To conclude, the various genera in the Pinaceae family can be propagated with a minimal amount of supplemental heat, but those in the Cupressaceae benefit from higher temperatures and a humid environment. I should add that this recipe has been developed at Buchholz Nursery with success, but perhaps a different propagator in a different location...
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