Friday, February 9, 2018

Winter Maple Propagation

I have owned a wholesale nursery for 38 years, which is unusual since I am only 39 years old. Over the course of the years we propagate by grafting in both summer and winter...and here we are: well into February and I'm trying to wrap up my 38th winter season. These "years" don't consider that I previously grafted for other companies, so ok, I confess that I'm older than 39. What to graft, how many to graft, what rootstocks are available at the correct size??? – nobody in the company has a clue what to do if I'm not here. Believe me, I'm not trying to boast about my importance; and really I am stating the sad fact that I have created a company that cannot operate without me...which is not a comforting prospect for this old geezer.

Acer x conspicuum 'Phoenix' in August
Acer x conspicuum 'Phoenix' in January

Acer x conspicuum 'Phoenix'

We've had a mild winter and soon spring will engulf us. Before it's too late I committed to grafting our stripe-bark (AKA snake-bark) maples. Acer x conspicuum 'Phoenix' is the cultivar in greatest demand, so it took up the majority of the rootstock (on A. davidii). I have a love/hate attitude towards 'Phoenix' – I love the winter bark of course, but in summer my oldest specimen planted next to the house looks dreadful after a 100 degree day. It's not that the leaves burn, but rather all of the green is bleached away and so I have to look at a yellow tree from July through October. Some years the autumn foliage is vibrant, but most of the time it goes from yellow-to-brown. If you grow 'Phoenix' in shade the leaves will be protected, but then the winter bark color will be dulled. I gave up growing 'Phoenix' as a field crop, and now all of our plants are produced in a greenhouse under white poly. They grow too fast that way, so we prune the new growth in half around August. The x conspicuum hybrid is Acer davidii x Acer pensylvanicum which would be hardy to -20 degrees F, USDA zone 5, however the 'Phoenix' cultivar is probably less hardy, which is usually the case for such freaks of nature.

Acer pensylvanicum 'Erythrocladum'

Elaeagnus 'Quicksilver'
Speaking of freaks, nothing can be moreso than Acer pensylvanicum 'Erythrocladum', a maple that I consider to be more problematic than A. x conspicuum 'Phoenix'. In the Hillier Manual of Trees & Shrubs (2014) 'Erythrocladum is called, "A lovely form with brilliant candy-pink, white-striated young shoots in winter." Lovely indeed, unless the shoots are black from death. I grafted 50 anyway since they are so easy to sell, but they'll spend their formative years in our greenhouse, and never see the outdoors until they are in somebody's garden center. 'Erythrocladum' received the Award of Merit in 1976, but I can't imagine that it performs better in wet foggy England than in Oregon. In my career I have questioned quite a number of Awards of Merit, and I actually wonder if money is changing hands under the table. Take Elaeagnus 'Quicksilver' which received the AM in 1978: It took a few years and a lot of effort to get rid of mine; it was looking scrappy so I cut it down, but 50 feet away the suckers kept popping up. 'Quicksilver's' place might be at the edge of a woodlot, but certainly not in a "garden."

Acer pectinatum 'Mozart'

Anyway, back to maples. We grafted 50 Acer pectinatum 'Mozart' (which some list as a conspicuum cross). It takes full sun in Oregon and so far has proven hardy. In winter the bark is purplish-red with white vertical stripes. I have seen photos inside an enormous Dutch greenhouse operation where thousands of 'Mozart' were being grown from rooted cuttings, but I wondered how hardy they would be. According to De Beaulieu in An Illustrated Guide to Maples, Acer pectinatum is native to the southern Himalaya, from Nepal, Bhutan, northern Myanmar to Yunnan, China. That doesn't sound very hardy. The subspecies forrestii is from Yunnan Province in the Yulong Mountains and is perhaps more hardy. It is said (Hillier) that 'Mozart' was "Raised from seed wild-collected by Peter Vanlaerhoven." If that is the case, then it certainly can't be an x conspicuum hybrid (A. davidii x A. pensylvanicum). Most of my maple market is in regions more cold than Oregon, so the botanic status is very important. DeB. continues: "In 1977, Murray regrouped four species – Acer forrestii, A. laxiflorum, A. maximowiczii, and A. taronense – under A. pectinatum, which is the oldest valid name among them." Note that A. maximowiczii is not the same as A. maximowiczianum (formerly A. nikoense). The former is in the Macrantha section and the latter is in the Trifoliata section (with A. griseum) and they are completely different.

Acer caudatifolium 'Variegata'

I also grafted a few Acer caudatifolium 'Variegata', a pretty thing even though its cultivar name can't be valid. This is another case where the botanists are not friendly with the gardener, because care must be taken to not confuse the A. caudatifolium species with A. caudatum. The former is in the Macrantha section and the latter in the Parviflora section. A. caudatifolium (formerly A. kawakamii, A. morrisonense) is from mountain forests in Japan, while A. caudatum is from China and Manchuria. Remember, we are talking about stripe-bark grafting, and A. caudatum is not a stripe-bark. I grafted only five scions of the A. caudatifolium 'Variegata' to be sure I keep it on the Ark when I plant the mother tree into the arboretum. I don't know if it will prove hardy enough, but what else can you do when its canopy is pushing into the top of the greenhouse?

Acer davidii 'George Forrest'

Acer davidii 'George Forrest'

Acer forrestii

Nomenclatural confusion continues when you consider Acer davidii 'George Forrest' and A. forrestii, and though both are stripe-barks they are not one and the same according to Hillier. 'George Forrest' ('Horizontale') is "An open tree of loose habit with vigorous, spreading branches and large, dark green leaves with rhubarb-red stalks. This is the form most commonly met with in cultivation." This "cultivar" was introduced by George Forrest from Yunnan in 1921-22. Acer forrestii was also introduced from Yunnan by Forrest in 1906. Are these really two separate species? The photos of 'George Forrest' were taken in England 15 years ago, while the photos of A. forrestii were taken recently at the Rhododendron Species Botanical Garden in Washington state.

Acer davidii 'Serpentine'

I have been growing Acer davidii 'Serpentine' for a long time, although I only propagate about every third year. It is a fast-growing cultivar and I suppose with time it would get huge. The colorful bark is most evident on young shoots, so it is probably better grown as a bush rather than as a large upright tree. That's another way of saying that sales are not so hot for fast-growing stripe-barks.

Acer tegmentosum 'Joe Witt'

Acer tegmentosum 'Joe Witt'

I attended a Maple Society conference in Belgium six or seven years ago and the most eminent Acer botanist of our time declared that Acer tegmentosum comes true from seed, and that there is absolutely no variation and therefore no cultivars of the species. Immediately a half dozen hands shot up to protest the know-it-all, and everybody said, "What about A. tegmentosum 'Joe Witt'? The botanist conceded nothing, and to this day is sure that 'Joe Witt' is undoubtedly a hybrid. Maybe it is. It was raised from seed by Mr. Witt, curator at the Washington Park Arboretum in Seattle. He planted it at his home where it grew fast and strong, and was one day noticed by visiting plantsman Dan Hinkley. Hinkley thought it was remarkable for its chalk-white bark, so he named and introduced it. 'Joe Witt' can be grafted onto any stripe-bark maple, and we have even rooted it with summer cuttings under mist.

Acer davidii 'Serendipity'

Acer davidii 'Serendipity'

Joe Witt passed away a number of years ago, and by chance his daughter worked at Buchholz Nursery for a few years. When her mother aged the decision was made to sell the family home, but I wonder if the new occupants recognize and prize their famous maple. On the property was a companion to the Acer tegmentosum – it was an Acer davidii seedling, also from the Arboretum. Witt's daughter asked if we could propagate the davidii as a memory to her father. She named the selection 'Serendipity' for a reason that I cannot remember. If anybody would like a start of that, or of the tegmentosum 'Joe Witt', just let me know.

Acer pensylvanicum 'Silver Fox'

Acer pensylvanicum 'Silver Fox'

The final stripe-bark that I'll mention is Acer pensylvanicum 'Silver Fox', a selection from Crispin Silva of Oregon. The "Moosewood" maple is the only native American stripe-bark, and 'Silver Fox' displays a trunk that commands attention. As with the others I've written about, I don't propagate many nor do I do it every year because my customers prefer exotics versus native American species.

The exotic maples we propagate in greatest number are of course Acer palmatum cultivars, but about 95% of them are grafted in summer when the heat is free. In the winter we place the grafts on our hot-callus pipe, and though the heated water in the pipes is certainly not free, last year virtually every graft "took" so I hope for the same this year. I know the risks, for the Gods of propagation like to toy with you to keep you humble. If they all live again this year I should probably buy a lottery ticket.

Acer palmatum 'Marlo'
Acer palmatum 'Taylor'

Some palmatum cultivars are too thin and soft in the summer, so these are the candidates that we winter graft. A.p. 'Marlo' is relatively new (for me) and it is very colorful, and it has effectively replaced the patented A.p. 'Taylor' because the latter is more prone to mildew. I received my start of both cultivars from Holland, and while I know that 'Taylor' is a Dick van der Maat selection, I don't know about the 'Marlo'. Anyway 'Marlo' grows as a bush about as wide as tall. It needs some protection form the sun in Oregon, in fact I consider it to be a patio plant in a container where it will also receive winter protection. 'Marlo' – I think named for a girl – is like a high-maintenance woman: very pretty when happy, but the guy has to decide if she's worth the effort.

Acer palmatum 'Tattoo'

While I was searching for another maple in the greenhouse I noticed my original start of A.p. 'Tattoo', a compact miniature spreading bun. I noted dozens of one-inch shoots that I had somehow overlooked in summer, and these little twigs were promptly dispatched to Juana in the propagation room. She makes every graft successful it seems, no matter how small or difficult the scion. I don't know the origin of 'Tattoo', or of its curious name, but if someone claims that it was a seedling or a mutation from A.p. 'Mikawa yatsubusa', that would be believable. A fantasy plant that I can imagine would be a red-leaved 'Tattoo', but I've never seen seed on my green specimen. For a while there was a false 'Tattoo' in the trade; I had it and it wasn't very impressive. Then the late D. Dodge of Bethlehem Nursery in CT – well, before he was "late" – gave me my start of the real deal. Mr. Dodge operated a small nursery, but one with a choice collection of maples, ginkgo and conifers, and my source records indicate that I received over fifty wonderful plants from him. So, in that sense he lives on...and I should do likewise.

Acer palmatum 'Wild Fire'

Basically, winter maple propagation involves me walking around the nursery with plastic bags and a pair of felcoes. I cut what I encounter and I can make an excuse for most everything. Such is the case with A.p. 'Wild Fire', and with the leaves out of the way it is more simple to choose good scionwood. I remember back a few months ago that I was impressed with its bright yellow fall leaves. Now the stem colors range from yellow to orange to red at the tips, and really it is more interesting than the ubiquitous 'Sango kaku' ("coral tower") which we stopped growing altogether.

Acer palmatum 'Bihou'

Another coral bark A. palmatum is 'Gold Digger', and it displays green leaves that evolve from yellow to red in autumn. The summer shoots stay yellow on my young plants, and I'm curious how evident this will be as the trees age. Both 'Gold Digger' and 'Wild Fire' can probably tolerate more cold temperatures than the popular Acer palmatum 'Bihou', but we sell a lot of the latter in Oregon, Washington and California.

Acer palmatum 'Peve Starfish'

Acer palmatum 'Japanese Princess'

I try to keep my propagating numbers reasonable, meaning that it is better to sell out of a cultivar down the road than to have too many. My customers are fickle for the most part, and it is their right to be. We could have propagated twice as many Acer palmatum 'Peve Starfish', a plant currently in great demand, and at least five times as many 'Japanese Princess', which is also in great demand, but I resisted the temptation to graft more. I remember in 2007, a year before our great recession, that a large Oregon wholesale nursery limited their customers on maples to only 30% of their total order. Some of their customers were trying to order maples only, and then buy their Hydrangeas and Alberta spruce elsewhere where the price was better. I found that amusing, to try to force your customers into supporting your other plant material. My customers can order whatever they want, and I'm pleased to be able to supply them, and it's my job to mind-read their future wants when I propagate. Feel free to "cherry-pick" at Buchholz Nursery; after all we only grow the cherries.


  1. Thanks, as always good stuff. curious, When will you be listing the new stock for sale?