Picea breweriana S.Watson

Picea breweriana is one of the more fascinating members of the genus. Long considered distinct from any other spruce, phylogenetic work has demonstrated that it occupies a basal phylogenetic position, morphologically and genetically distinct from any other species (Lockwood et al. 2013). Befitting this position it is a true relict, confined to a relatively small area in the Klamath and Siskiyou Mountains straddling the borders of NW California and SW Oregon in the United States. Partly on account of its narrow area of distribution, where it exists in small, scattered stands rather than in expansive forests, it is categorised as Endangered by the IUCN, the principle threats being forest fires and climate change, which might render parts of its already-small range unsuitable for it by the end of this century (Nelson, Farjon & Thomas 2019).

This species was discovered in 1863 at Black Butte, west of Mount Shasta, by the American botanist William Henry Brewer, Professor of Botany at Yale, but it would not be described to science until it was refound by Thomas Howell in 1884. The earliest documented introduction took place in 1891, when a Mr R. Douglas of Waukegan, Illinois, visited Oregon and collected ‘a large quantity of cones, from which several hundred thousand seedlings were grown’ (Elwes & Henry 1906–1913). Whether or not this is an exaggeration matters little, for it seems that none survived in America long enough to make a sapling, let alone a tree, although a few plants were raised in Europe by Baron von Saint Paul Illaire (for whom the genus of African Violets previously treated as Saintpaulia was named) and a few specimens survived on the family estates in central Europe into the early 20th century, although their ultimate fate is unknown (Elwes & Henry 1906–1913). Also in the late 1880s or early 1890s the Oregon nurseryman Mr Johnson of Astoria transplanted several young trees to his nursery, and it was from this source that, via Professor Sargent at the Arnold Arboretum, a single tree arrived at Kew in 1897 (Jacobson 1996). It survived near the Pagoda until the mid-1990s ‘a gaunt object, no advertisement for the species’ (Mitchell 1996).

At its finest, when mature trees bear foliage branchlets that hang vertically like heavy curtains from the elegantly bowed main branches, Picea breweriana is among the most striking of temperate conifers. Like several others with weeping branchlets, such as Callitropsis nootkatensis, Cupressus cashmiriana and Picea smithiana, the effect is elegant and beautiful, and in a garden setting it can produce an aesthetic with few rivals. It is an easy spruce to recognise thanks to the unique combination of rather long, flattened needles, green above with white stomatal bands beneath, being radially arranged on the flexible, pinkish brown shoots; only P. smithiana is likely to be confused with it, but that has needles similarly coloured on all surfaces, not spreading so widely from the pale cream-white shoots (Mitchell 1972).

For all its ornamental qualities, Picea breweriana has one significant draw back; it is extremely slow growing. Seed-raised plants spend many years putting on only a few centimetres annually. They might reach 30 cm in as few as five years or as many as ten, irrespective of whether they are grown in open ground or containers. Even cultivation in Air-Pot^© containers does nothing to accelerate growth (pers. obs.). Long after planting out progress remains infuriatingly slow, and unless well maintained, plants are vulnerable to being overwhelmed by competing vegetation. After several to many years plants start putting on respectable annual increases in height, and whilst it might seem a big improvement it might only amount to 10 or 20 cm per year, and is not always vertically upward. This can create a somewhat awkward looking young tree, but worse than this, the pendulous second order branches and branchlets for which the species is almost solely grown do not start to develop their unique habit until trees are well established, often 20 or more years old. Until then, the first order branches ascend and the crown appears relatively sparse, which might often call their identity into question.

To get around this problem – and to modestly increase growth rates – nurseries graft scions from established trees, well into their pendulous ‘adult’ phase, onto young rootstocks. The effect is difficult to manage and hideous to behold, but nurseries and garden centres across the temperate world sell thousands of such plants every year, blind to the fact that they scarcely do a greater disservice to conifers than plastic Christmas trees. For many years grafts are dumpy, gawky, and graceless, with erratic spiky branches going off in odd directions. This handicap lasts for years, and even long after grafts begin to make decent trees and develop a reasonably respectable overall shape, the upper crown continues to look totally at odds with the rest of the tree.

One of the reasons such plants pass muster is that young seed-raised examples are so rare few people have ever seen one, and so they have nothing to compare the grafted versions with. Raising Picea breweriana from seed is simply not commercially viable for most modern nurseries, and only enthusiastic specialists would entertain the idea. Even then, seed is difficult to come by, and even the most knowledgeable growers can lose patience; the late Alan Mitchell evicted one from his own garden when, after 11 years, it remained only waist high (Mitchell 1996). Although the species has become much more popular since the mid to late 20th century, most specialist collections are still only likely to grow a few examples for display and education purposes and so are more likely to buy in plants than to go to the trouble of obtaining wild-sourced seed. A notable exception is the Royal Botanic Garden Edinburgh, which has multiple known-wild-origin accessions distributed across various partner sites participating in its International Conifer Conservation Programme (ICCP) and at Dawyck Botanic Garden in the Scottish Borders. Some of the most significant plantings of P. breweriana established by the ICCP include those at Cragside (Northumberland, UK) where over 40 trees representing several different accessions were thriving in a large, naturalistic planting when last monitored in 2017, creating a truly beautiful scene (pers. obs. 2017).

Within the UK, Dawyck has always been an important garden for Picea breweriana. Three of the UK and Ireland’s ‘top ten’ examples grew here (they are currently dying at an alarming rate following attacks by the Great Spruce Bark Beelte – see below), including the champion for girth, planted in 1908 and 23.5 m tall × 89 cm dbh in 2014. This is also the second tallest known, the record going to a tree at Glen Tanar, Aberdeenshire, 27 m × 74 cm in 2018 from a 1922 planting (Tree Register 2024). R.F.S. Balfour of Dawyck was a keen dendrologist and forester and accompanied Professor Brewer on several expeditions to study the tree in the wild and to remove young seedlings to worthy sites for fear of its long-term future as a wild tree (an early example of ex-situ conservation) (Mitchell 1996). Balfour brought seedlings home to Dawyck in 1906 and 1908, from which the majority of Dawyck’s mature examples are derived, and then in 1911 he received, to his surprise, many more in a box made from the wood of Calocedrus decurrens, sent by a farmer with whom he had stayed on an earlier trip. Balfour kept some, but the majority were surplus to his needs and were distributed amongst dendrologically-inclined friends, and many of the biggest and best extant examples in Britain are ‘Balfour trees’ (Mitchell 1996).

Although there are still some fine old trees in the south of Britain, in cultivation Picea breweriana appears to prefer cooler conditions than now prevail there and the best specimens are concentrated in the north. Although preferring high rainfall and humidity, it will not tolerate wet ground, and is happiest on an acid soil. It is not well adapted to a continental climate; only a single tree was reported from the Arnold Arboretum in 1982 (Warren 1982) and today none are extant there (Arnold Arboretum 2024). This echos Dirr’s observation that there are very few good trees at all in the eastern United States, but he heaps praise upon a beautiful stand of trees growing in the Hoyt Arboretum, Portland, Oregon (Dirr 2009). P. breweriana seems to grow better in continental Europe than it does in the continental central and eastern United States; in 2022 there was a tree 18 m × 47 cm in Pfaueninsel, Wannsee, Berlin (Monumental Trees 2024) while the Beltrees database lists fewer than 20 notable examples from Belgium, the tallest 14 m and the largest 38.5 cm dbh (Arboretum Wespelaar 2024).

At least in Britain, Picea breweriana has been observed to be particularly vulnerable to windthrow, and in more recent years mature examples at Dawyck have been targeted by outbreaks of Great Spruce-bark Beetle (Dendroctonus micans) (Royal Botanic Garden Edinburgh 2023). The beetle seems to have a particular fondness for Brewer Spruce, and the tree a particular weakness, for several of Balfour’s original trees, among the finest in cultivation anywhere in the world, have gone from perfectly healthy to standing dead in as little as eight months (G. Stewart & T. Gifford, pers. comms. 2024). It beggars belief that experimental stem injections – which might have prolonged their lives as they have done many other heritage trees in other parts of the world – are still not an option in the UK.