Pine Commentary

Noted British horticulturist Brian Humphrey, now in his 80's, is writing a book on propagation. We're not close friends – he has been to my nursery once (long ago when I was young) and I have been to his place once in East Anglia – but we used to trade plants when that was less troublesome, and we still correspond, most recently about plant propagation.

RHS President Elizabeth Banks awarding Brian Humphrey with the VMH

Mr. Humphrey was a 2012 recipient of the Royal Horticultural Society's Victoria Medal of Honour (VMH), and that's a big deal since only 63 horticulturists hold the VMH at one time, marking the length of Queen Victoria's reign. He trained at Royal Botanic Gardens, Kew, and he has worked for Hillier Nurseries and Notcutts Nurseries before starting his own nursery, propagating and growing rare and unusual plants. He was also a founding member of the International Plant Propagators Society of Great Britain and Ireland and became its first President.

While working on a section about pine propagation he posed an interesting question:

Dear Talon,
In the course of a literature search on pines I have come across a report in a Dutch paper 1988-89 period, on how pines are grafted in Japan. Two surprising facts come out. One, perhaps not so surprising is that their grafting methods involve apical grafts, usually what we would call wedge or cleft, a few Europeans do that over here, but the second is that once grafted they are placed in complete darkness for 4 to 6 weeks. This would seem to break all the rules of pines requiring high light levels etc. etc.

Do you have any knowledge of this and whether or not it is still practised in Japan? On the face of it it seems to be a good way of guaranteeing zero takes but obviously this cannot be their experience. Also surprising is that they graft some of their five needled pines onto P. thunbergii for Bonsai production, this seems against all the rules as well.
Perhaps Haruko can comment?
Best wishes to you both,
Brian

Pinus thunbergii var. corticata

I responded as follows:

Haruko is familiar with pine grafting for bonsai, but she doesn't know anything about keeping the grafts in the dark, nor do I. Maybe I'll try a few this winter and see if anything lives.

I suppose the value of a wedge graft – versus the typical side graft – is to get the union as low as possible, and maybe the wedge portion heals less conspicuously than cutting off the rootstock stub on a side graft. Anyway I've never done a wedge graft for a pine, but again I think I'll do a couple this winter.

Pinus thunbergii var. corticata 'Tsukasa'

One reason for using P. thunbergii for rootstock is that it grows faster than 5-needle rootstocks, and the "flair" at the base of a bonsai specimen is highly valued. Of course a bonsai master has tricks and techniques to make it all look natural. P. parviflora is compatible with P. thunbergii and I have known growers in Oregon who have succeeded with it, and also with P. mugo as rootstock. The mugo is a better rootstock for a parviflora scion if plants are to be grown in containers. Also it is very hardy, more so than P. thunbergii. What these grafts look like 20 years later I can't say. Another problem with P. mugo is that it is difficult to get a straight section of trunk that is low in the pot.

My old Dutch nursery boss

I mention the old Dutchman I worked for from time to time. He assumed he knew everything horticultural because...well, he was Dutch. He told me once that you cannot graft in a poly house – it must be in a glass house. Each night I would return home from my job with him and successfully graft in my poly houses. Also, when I brought up the subject of grafting 5-needle pine onto 2-needle rootstock he grew absolutely disgusted with me and my ignorance. "You cannot graft 5-needle onto two-needle!" he thundered.

The Dutchman died about 20 years ago and he was soon thereafter enshrined into the Oregon Nursery Hall of Fame. I never will be because I am considered too irreverent.

Haruko has the ability to google in Japanese and she came up with a few websites or YouTube videos that show Japanese bonsai masters in action. She prompted me to search and I watched a few in English, so you might find something yourself.

Haruko and I would love to travel and visit England again. The problem is that we are prisoners of our 14-year-old's professional ballet career. The competition is intense and she can't miss any time. She is too young to drive to classes and so Haruko is practically a full time chauffeur – at least 4 hours per day, six days a week.

You are always welcome to visit us in Oregon though, but you must promise to drive on the right side of the road!

Take care,

Talon Buchholz

--------------------------------------------------------------------------------------------------------------

Dear Talon,

Many thanks to you and Haruko for your reply. How interesting that she too was not aware of this curious procedure. I am sure the Dutch have gleaned the right information from somewhere but they give no source. Japanese nurserymen are obviously keen on their wedge grafts, virtually everything we had at Hilliers or Notcutts as grafted material from Japan involved wedge grafted material, same can be said for the Chinese. I have a few Dutch (Boskoop) nurseryman friends and will see if they know of this system.

I have attached a PDF of the chapter on Pines for your interest. As always if you have time to add comments or criticism it is always welcome.

Brian Humphrey is one of the few people who actually reads the Flora Wonder Blog, and he's never been afraid to comment, criticize and correct me for my mistakes, a service which I actually appreciate, so I'll add a few comments about what he writes:

“As Pines are extremely difficult to induce to root from cuttings grafting procedures are necessary to produce most cultivars...”

Pinus mugo 'Jakobsen'

I would agree with the above summation except for the significant practice of rooting Pinus mugo cultivars. At least one Oregon Nursery roots mugos by the thousands with 'Slowmound' being very popular, and I have seen their impressive crops with my own eyes. I have attempted to root other cultivars myself, but I haven't been very successful, however my research into the matter indicates that particular cultivars are more inclined to root and that timing and hormone strength also factor into the results. Oregon State University was conducting experiments as early as the 1960's.

Pinus sylvestris

But in any case I prefer to graft mugo cultivars because I don't grow them by the thousands and the few that I produce are faster to market when grafted onto an established 3-year-old Pinus sylvestris rootstock. Humphrey mentions that at the Trial Station at Boskoop in Holland (Prefstation voor de Boomkwekerij), “Surprisingly P. sylvestris is suggested as a better rootstock than P. mugo for many P. mugo cultivars, a conclusion likely to be widely contested by many Dutch conifer grafters.” Again, I prefer sylvestris because it is difficult to find a straight section on a gnarly mugo trunk.

Chamaecyparis obtusa grafted on Chamaecyparis lawsoniana
showing long-term incompatibility

I have P. mugo cultivars that were grafted onto P. sylvestris nearly 40 years ago and the compatibility is not an issue. Nevertheless, I agree with Humphrey's conclusion:

It is hard to summarise the above results and conclusions. It seems to be the case that often long term incompatibility is masked by combinations inherently incompatible but which survive and grow with varying degrees of success for periods of time. Unfortunately nurserymen may be guilty of perpetuating misconceptions as apparently successful combinations survive nursery life only to fail at some point in the future. While the pines do not pose such a challenge in discovering the secrets of graft compatibility as some of the hardwood genera, they do present problems which may take many years of patient investigation to overcome.

I like the suggestion that “nurserymen may be guilty...” Of course! Nurserymen are often guilty.

In his introduction to Pinus (Pinaceae) Pines Humphrey refers to “A limited number [of pine species] produce edible seeds, sought after by gourmets but also in past times an important food source for some American Indian tribes.”

Pinus monophylla

I can think of 17 species that produce seeds large enough to be worth harvesting, and there could be others that I am overlooking. They include:

P. pinea	patula
gerardiana	coulteri
koraiensis	torreyana
siberica	lambertiana
pumila	quadrifolia
bungeana	cembroides
cembra	edulis
sabiniana	culminicola
monophylla

Pinus pinea

Pine nuts produced in Europe mostly come from P. pinea which has been cultivated for its nuts for over 5,000 years, and harvested from wild trees for far longer. Greek authors mentioned pine nut trees as food producers as early as 300 B.C.. Roman soldiers took them (P. pinea) as campaign food when they raided Britain over 2,000 years ago. Pine nuts contain 10-34% of protein depending on species, with P. pinea having the highest content. Although a “nut” in a culinary sense, in the botanical sense pine nuts are “seeds.”

Pinus cembra 'Glauca'

European pine nuts are distinguished from Asian by their greater length versus width (Asian pine nuts are stubby like long kernels of corn). In Italy they are called pinoli and are an essential component of Italian pesto sauce. Pinoli cookies (biscotti ai pinoli) are made of almond flour and then topped with P. pinea nuts. In Catalonia a sweet (panellets) is made of small marzipan balls covered with pine nuts, then painted with egg and lightly cooked. In Middle Eastern cuisine pine nuts are used in various dishes and in desserts such as baklava. By the way Pinocchio is the Tuscan (Florentine) word for “pine nut,” from Latin pinuculus.

American pinyon pine production occurs between 6,000'-8,000' elevation with the ideal at 7,000'. Humidity encourages cone development, such as in shaded canyons. Where humidity remains constant throughout spring and summer the cones fully mature and produce the best seed.

Pinus edulis

Pinus edulis was harvested by the Navajo people and was once used as a means of commerce. In recent times the nuts are harvested and one can purchase them at roadside stands in the American Southwest. I think I remember paying $16.00 for a pound, which seems like a lot of money at first, but then not really when you think about it. For some American species the 2-year cone is harvested in late summer while still green, then they are placed in burlap bags and exposed to heat (like the sun). It takes about 20 days until the cone fully opens. Strike the burlap bag against a hard surface, then separate by hand the seed from the cone residue. I bought my pound from a Native American, but there was no way he could identify the species as he wasn't versed in Latin nomenclature. One treat that I remember in New Mexico was a pine nut coffee known as pinyon, but it was heavy and a spoon practically stood up in the cup.

Pinus armandii

If one orders a high-end salad that contains pine nuts, they probably came from China which is the largest supplier in the world. You are advised to nibble at a few at first to be sure that you don't suffer from PNS (pine nut syndrome) and indeed the labelling on a package I purchased recently for this blog warns “Some individuals may experience a reaction to eating pine nuts, characterized by a lingering bitter or metallic taste.” Some victims maintain that the “lingering” can remain up to a month. Some Chinese exporters admitted in the past to mixing the edible P. koraiensis with the inedible P. armandii. The latter are deemed “unfit for human consumption” by food safety experts at the European Commission. Most of us can't tell the difference between P. armandii and P. koraiensis – the trees, that is – but I remember seeing a pile of cones in Yunnan, China that were harvested as food from P. armandii or so I was told. Maybe that was the bad batch that caused the metal-mouth. To be fair to the Chinese, my recently purchased bag of Dry Toasted Pignolias from the Trader Joe's chain is listed as a product of Korea, Russia and Vietnam, although it was roasted in the USA. Nowhere on the bag is the species of pine mentioned, and I am probably the only person on earth who cares or would think to question.

Pinus koraiensis 'Morris Blue'

Pinus koraiensis 'Oculis Draconis'

So I assume that my nuts are from P. koraiensis, a northeast Asian species introduced by J.G. Veitch in 1861. Besides the nuts the species is valued as a hardy, soft-needled pine (needles in fascicles of five) with wonderful horticultural merit. Some of the cultivars include 'Silveray' and 'Morris Blue', selected for long bluish-green foliage. 'Dwarf' and 'Nana' – both terrible names – possess gray-green foliage and a more slow rate of growth. 'Jack Korbit' and 'Oculis Draconis' display yellow banding on the needles and are most evident when trees are grown in sparse growing conditions, at least more sparse than at Buchholz Nursery.

Panthera tigris altaica - By Appaloosa - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8890924

“Korean pine is recorded in north-east Asia, from Korea, Manchuria and adjoining Pacific Russia” according to Rushforth in Conifers. He continues that “It has a valuable timber and also provides edible nuts. Unfortunately its habitat is being reduced by logging, both legal and illegal. And it's not only people who will suffer from over-logging. The mixed deciduous forests of northeast Asia that contain P. koraiensis are important for the Siberian (Amur) tiger – Panthera tigris altaica – because they sustain the tiger's prey. Pine nuts are a valuable source of food for deer and wild boar, the tiger's primary prey. I'll bet that modern Western gourmets never gave a thought that their tasty salads with pine nuts would endanger the magnificent tigers!”

So, there you have some of my rambling thoughts about Mr. Humphrey's upcoming book, which is probably not at all what he was hoping for. Maybe I am masking the fact that I don't really know too much – at least empirically – about pine propagation. Largely I have copied others in my career. I am further enlightened by the likes of Brian Humphrey, and I always learn something interesting from him.... But growing pine grafts in the dark? – that was a complete surprise.