Grafting Picea, Winter 2023-2024

Picea abies

Hey, let's spruce it up! We finished our Picea grafts a couple of weeks ago, and now they huddle under a thin layer of construction poly in the greenhouse. Can't be the heavy poly like we use to cover the outside of the greenhouses. The rootstock of choice – for all the species and cultivars – is the “Norway spruce,” Picea abies. In my experience it is highly graft-compatible, extremely winter hardy and a much better container dweller than any other Picea species. Even when propagating the many cultivars of Picea pungens, still Picea abies is superior compared to the like species. Our container media is ten parts medium-grade “Douglas fir,” Pseudotsuga menziesii and one part #6 pumice, and absolutely to the spruces' liking. Generally our media is considered coarse with excellent drainage so we must irrigate more than probably most nurseries, but we have plenty of water. Peat moss and/or sand is never incorporated, and our Piceas thank us that they can thrive without those unnecessary, expensive media amendments.

Cleaning scions

We prepare the rootstock the same way as we did the two-needle pines discussed in the previous blog, where all the side shoots are removed and the short, thin needles at the base of the trunk are cleaned with the fingers. We count the prepared understocks for the exact number, and that becomes our pie to split, some going to this and some going to that. Jordan cut the majority of the scions and Jazmin completed the thankless task of “cleaning” the base of the scion so the grafter can cut. “Cleaning” the scion is a Buchholz Nursery term, but really it's a scraping of the scion base with a knife, and care must be taken to not overly scar the scion, especially as some can be very thin.

Picea engelmannii 'Snake'

Picea engelmannii 'Snake'

Picea engelmannii 'Snake'

There were two spruces that I wanted to cut myself. I needed to focus and didn't want to get distracted by trying to explain. The first batch was from Picea engelmannii 'Snake' and we had only one 8' tree as stock. 'Snake' grows as the name implies with long whip-cord branches, but one must not over-harvest or you'll be short changed the following year. The problem is that where the scion is cut it will not resprout, the remainder of the shoot will die. The reader would probably follow me better if we were both looking at the tree, and as for Jordan, our new horticulture manager, I took him back to our stock and explained my theories the next day. 'Snake' is best described as bizarre, with no two looking alike. I even had one reach to 12' tall with only one stem, with absolutely no side branches. Obviously there was no propagating from the solo pole, and to keep it growing upward a heavy metal stake was used to protect it from wind or snow. Someone eventually talked me out of the tree – and he paid a handsome price – but after it was dug and shipped I truly regretted parting with my queer friend.

Picea farreri

I also worked alone – it only took a minute – to harvest from my original plants of Picea farreri. Again, I couldn't be greedy; one must practice patience and allow the stock trees to develop, and there'll be plenty of scions down the road. “Farrer's spruce” is rare in cultivation, but then it's only hardy to 10 F, USDA zone 8 (at best). I think my stock trees are just four years old, and the scions were mostly very thin, so they were best cut by myself. I know Jordan will be more prepared to do it next year.

Reginald Farrer

Picea farreri was originally introduced by Reginald Farrer from northern Burma in 1919, and can be found in a few gardens in the mild areas of the UK. It is described as having a vertical trunk with long pendulous side branches with gray-blue needles with white undersides. Sadly, the spruce native to southern Yunnan, China and northern Myanmar is threatened due to logging. Sadly also is that poor Farrer (1880-1920) died while collecting plants in Upper Burma (probably of diphtheria) at the age of 40 and is buried in those mountains. Farrer was a rock-gardening pioneer and prolific author, but his prose is old-fashioned and laboriously flamboyant, best consumed with a hot toddy on a winter's night.

Jordan cutting scions

Ok, now it's Jordan's turn to cut the scions, and I'm happy to finally be free from bending low to cut the dwarves. I coach about what is the best type of scion for each cultivar, whether single-shoot one-year wood or two or three-year branched wood for some of the miniatures. Ideally Mr. J. would have had a couple years of grafting himself, and then the intricacies of scion cutting would become more obvious. I'm sure that at some point he will graft some, so he'll have to learn the process backwards.

Picea glauca 'Burning Well'

Picea glauca 'Burning Well'

Picea pungens 'Blue Pearl'

Picea pungens 'Blue Pearl'

There were a couple of miniature Picea cultivars that are appealing, but we (me and management) debated if we should grow the very slow, low-profit plants such as Picea glauca 'Burning Well', a low dense bun with a perky character, and Picea pungens 'Blue Pearl', a tiny, sparkling blue ball. In the end the plants prevailed...because they are so cute. But in neither case do we have much for scion cutting, and for 'Burning Well' Mr. J's interpretation on what to cut was far too thin and feeble. We threw those out then went back to the stock to reharvest.

Picea pungens 'Maigold'

Picea pungens 'Maigold'

Picea pungens 'Spring Blast'

Mr. J. had an easier time with a couple of medium-sized upright spruces that flush like a flower for about six weeks in spring. Picea pungens 'Maigold' (Maygold) is a blue-green tree for most of the year, but the new shoots begin a cream-white color, then evolve to a mellow yellow by May. When the heat of summer eventually arrives the spectacular spring flush has begun to evolve back to the old blue-green which saves it from burning. Similar to 'Maigold' is our introduction of Picea pungens 'Spring Blast', except that 'Spring Blast' blooms with white new shoots, and the bright needles contrast wonderfully with its pleasing blue older foliage. I encouraged Mr. J. to cut strong shoots; don't go too thin especially when you don't have to compromise.

Picea glauca 'Mac Gold'

Picea glauca 'Mac Gold'

Both P.p. 'Maigold' and 'Spring Blast' are challenging to stake and prune into ideal Christmas tree forms. A much more neat and formal upright spruce with the spring-bloom new growth is Picea glauca 'Mac Gold' (AKA 'McConnal's Gold'). New shoots are cream-white with just a hint of yellow, and sometimes a delightful, tiny red cone will join in the fun. We learned from past field harvests that 'Mac Gold' is mildly stressed after it is dug from the field, and that disturbance causes it to set numerous and very ornamental cones. Well done, and popular in the retail garden center. Hardy to -40 F, USDA zone 3, best in full sun.

Picea omorika 'Pendula Bruns'

Picea omorika 'Pendula Bruns'

Picea omorika 'Pendula Bruns'

One of my favorite conifers is Picea omorika 'Pendula Bruns' which I acquired in the 1990s. I assumed its origin was the Bruns Nursery in Germany but when I visited in 2000 Herr Bruns knew nothing about the weeping Serbian spruce. The company is well-known in Europe for large-sized specimen trees, so I found it remarkable that they weren't growing it. Maybe “Bruns” is a common name in Germany and I was at the wrong company? I was on a Conifer Society tour and a few days later we visited an arboretum – I forget the name – in the near vicinity of Bruns Nursery, and there I was delighted to find a large, impressive specimen of...yes, 'Pendula Bruns'! I speculated that perhaps an older generation of Bruns discovered the original tree and donated it to the arboretum before the younger Bruns took over the nursery. Well, we'll never know, but what complicates the issue is that there's a completely different conifer named just 'Bruns' (not 'Pendula Bruns'), a dwarf upright tree which I have never grown because 1) it might confuse my customers and 2) I don't care for it anyway.

North and South America Continental Divide

The first time I drove across the Continental Divide in the Colorado portion of the Rocky Mountains I didn't realize that the so-called “divide” actually extends from the very north Bering Strait down to the southern tip of South America at Patagonia and Tierra del Fuego. The divide separates waters that flow either to the east or to the west, and one fun place I would love to visit is The Parting of the Waters in the Teton Wilderness where one fork flows to the Pacific and the other flows into the Atlantic.

Picea pungens 'Continental'

Picea pungens 'Continental'

Picea pungens 'Continental' supposedly originated at or near the Continental Divide in Colorado, and it's a remarkable “Colorado Blue spruce” cultivar with a perfect Christmas-tree form that requires little or no pruning and staking. Needles are sparkling blue if planted in full sun with good drainage. 'Continental' is not dwarf at all, growing about 7-8' tall in 10 years...and topping out at about 25' at maturity. As with all the “shiner” Colorado Blue spruce, the silver-blue color is caused by a wax that covers the outer surface of the needles called a “glaucous bloom,” a wax that can be rubbed off with the fingers. In the few winters that we experience an Arctic Blast – near 0 F temperatures with up to 40 MPH wind gusts – the silver wax might disappear on the north side of the tree; but not to fear, for when the spruce resumes growing in spring the new shoots will display the blue again.

Picea pungens 'Coors'

Picea pungens 'Coors'

Besides Picea pungens 'Continental' as a non-dwarf upright spruce, we also grow Picea pungens 'Coors' which allegedly was discovered in Colorado on the grounds of the Coors beer estate. It's a nice story but I can't verify if true. The needles of Coors are equally as stunning, but they are more wide than 'Continental'. 'Coors' is much slower growing and needs more attention to pruning and staking to achieve a quality tree at about 5-7' tall in 10 years. Most of the cultivars are hardy to -40 degrees, USDA zone 3, but only if they are established in the ground. As mentioned earlier, all our Picea are grafted onto Picea abies which is even more winter hardy, but we've experienced losses in one-gallon pots (above ground) when the Arctic Blast event is long-lasting and severely windy. We used to grow more upright cultivars of Picea pungens, Picea engelmannii, Picea smithii and others, but they were routinely attacked by the “White Pine Weevil,” Pissodes strobi so we limit production in favor of more-dwarf cultivars that the culprit avoids.

Picea orientalis 'Skylands'

Picea orientalis 'Skylands'

Picea orientalis 'Skylands' is a slow-growing, golden form of the “Oriental spruce,” a species native from the Caucasus Mountains to Turkey. 'Skylands' originated at the Skylands Botanical Garden, New Jersey in 1975. The same plant was also peddled synonymously as 'Aurea Compacta' which is an illegitimate name due to the rules of cultivar nomenclature that prohibits the use of Latin since the 1950s.

Picea orientalis 'Lil' Sky'

About ten years ago I received starts of two dwarf, golden Picea orientalis from the late Dennis Dodge of Bethlehem Nursery, 'Sky One' and 'Lil' Sky', and I assumed they originated as seedlings from the mother tree of P.o. 'Skylands'. I can't tell them apart without labels, but both are wonderful, pyramidal uprights with the same color as the mother tree. Since they are similar I decided to focus on 'Lil' Sky' mainly because a 'Sky One' implies there could be a 'Sky Two', 'Sky Three' etc., perhaps confusing for the customer who just wants a unique plant. A woman attending a party doesn't want to find another woman, or lots of women, wearing the exact same outfit. In any case we grafted 100 'Lil' Sky', but would have done many more if our stock wasn't limited. The reason the stock was limited is because most of the containers have been ordered, awaiting shipment this spring. We could have used skinny, one-year shoots, but decided instead to use two-year, branched scions to create salable plants more quickly. Then the owner/propagator must choose a balance between making (much needed) money today versus adequate stock for future propagation.

Picea orientalis 'Tom Thumb Gold'

Picea orientalis 'Tom Thumb Gold'

If the conifer collector already has Picea orientalis 'Tom Thumb' then he doesn't need 'Tom Thumb Gold' because they're the same plant. I acquired my start as 'Tom Thumb' only, and I have sold a few thousand already with the incomplete name. So sorry. According to the American Conifer Society, 'Tom Thumb Gold' was discovered as a 4” witch's broom mutation on 'Skylands' by Halstead Wells, owner of Tom Thumb Nursery, New York in the 1970s. The photo above is from the Everts garden in Washington state, and is the largest I have ever seen at about 30” in diameter. My original stock of 'Tom Thumb Gold' was probably acquired as soon or sooner than Everts, but the problem is that I keep selling my best trees. The cultivar is particularly cute on a short 12-15” standard. Ultimately, whether low grafts or shorts standards, it prefers AM sun and PM shade in moist well-drained soil. We use two-year branched shoots for our scionwood and the graft takes are usually pretty good.

Picea pungens 'The Blues'

The original Picea pungens 'The Blues' at Stanley Nursery

One of my favorite conifers is Picea pungens 'The Blues', a weeping selection from the former Stanley and Sons Nursery, Boring, Oregon. A central leader can be staked as high as one wants to take it, and then side branches are allowed to droop downward forming a narrow weeping tree. Larry Stanley noticed a decidedly pendulous mutation on Picea pungens 'Glauca Pendula' that displayed a superior look compared to the mother tree, and if I recall, that was in about 2000. Larry gave his findling an excellent cultivar name, a very commercial name. Graft takes on one-year shoots are usually very successful and its not difficult to establish a leader. If the grower discontinues staking upward then the leader will wander sideways. It performs well in full sun or in partial shade in moist, well-drained soil. Thankfully, Stanley never patented his discovery, but sadly he and others suspect that some later, similar introductions (as in 'Slenderella') are in fact renamed and patented copies of 'The Blues'. Shameful for sure.

Picea abies 'Pusch'

Picea abies 'Pusch'

Picea abies 'Acrocona'

Picea abies 'Pusch' ('Acrocona Pusch' syn.) is a cute dwarf “Norway spruce” that forms a low, dense groundcover. Its claim to fame is that the plant develops numerous small cones in spring that rise above the foliage with a dazzling magenta color, like the plant is blooming red. Then by summer the cones evolve to brown and droop downward, where they will persist for the rest and into the following season. It originated as a witch's broom mutation on the prolific coner, Picea abies 'Acrocona', a mother tree that has fallen out of favor compared to its more-dwarf offspring. Discovered by Andreas Pusch of Germany, it received Conifer of the Year in 2008 by the American Conifer Society (ACS).

Picea pungens 'Ruby Teardrops'

Picea pungens 'Ruby Teardrops'

Picea pungens 'Herman Naue'

Picea pungens 'Herman Naue'

Picea abies is not the only species with dwarf cultivars with the coning instinct, we also have a few similar cultivars of Picea pungens: 'Early Cones', 'Ruby Teardrops' and 'Herman Naue'. They're similar, just that they were discovered and introduced in different places and at different times. 'Ruby Teardrops' is the more commercial of the names I suppose, except that the “teardrops” – when they are of “ruby” color – are positioned upwards. Oh well, nice name anyway, much better than 'Herman Naue'. All three selections are slow-growing, forming low, spreading buns that require about three years following the graft year to produce a full salable one-gallon. Besides, graft “takes” are never outstanding, and often the scion only produces one-or-two awkward side shoots. In other words: not highly profitable.

Picea glauca 'Pendula'

Picea glauca 'Pendula'

We continue to graft Picea glauca 'Pendula' because it's a wonderful, narrow weeping tree, but it is common now in the trade; in fact a new landscape at a burger-joint in Forest Grove has positioned them in a number of locations...and they look great in the scape. The tree that became 'Pendula' was propagated by D. Hill Nursery from a native stand in Ontario, Canada. It eventually was collected by the Morton Arboretum, Illinois, and has been grown there since 1958. It is an extremely hardy, easy-to-grow and useful tree that is popular with gardeners with a small lot size, and we have propagated close to 5,000 of them over the years.

Picea breweriana

Picea breweriana

Well, that's about one-half of the Picea cultivars that we produced this winter, but it's a broad spectrum of our favorites, both aesthetically and commercially.