Picea

These tidy evergreen trees are not just for Christmas and come in a range of shapes and sizes, writes Miranda Kimberley.

P. abies ‘Pusch’ - image: Floramedia
P. abies ‘Pusch’ - image: Floramedia

The spruce is one of our most well-known trees, as the Norwegian species graces hearths and homes around the world for Christmas. Seen as the traditional Christmas tree, it remains highly popular, only beginning to be rivalled by non-drop trees such as the Nordmann fir. 

Picea is a fantastic genus, all year round — not just for Christmas. They are a group of tidy, conical evergreen trees, offering a range of shapes and sizes with their varieties in shades of green and grey. There are many distinctive dwarf forms, particularly of the Norway spruce, P. abies.

There are 35 different species of Picea throughout northern temperate regions, with a particularly large number in East Asia. They are found either up mountains or on wet plains. Tree heights range from 20m to 60m or beyond in some cases. 

Branches are whorled around the trunk and come out horizontally. Their leaves are short and needle-like and leave a small protrusion or "peg" on the branch after they fall, leaving the branches rough to the touch. This is a distinctive feature that distinguishes them from the superficially similar genus, Abies. They also differ by having pendent cones. Picea have both male and female cones, which ripen in the first year and then usually fall at the end of the following year.

Because of their natural habitat, their ideal general conditions are in acidic, damp but well-drained soil. However, most can cope in a variety of soils, with some species even tolerating limestone.  P. omorika Award of Garden Merit (AGM) can even be planted in chalky conditions. 

Most prefer to be planted in areas of high rainfall, though species such as P. pungens and P. asperata that come from high mountainous regions prefer conditions cold and dry. As a result, Picea will thrive in Scotland — P. sitchensis has been known to reach more than 60m tall there. But as Kew’s Tony Kirkham comments, they are finding it hard in southern England because conditions are becoming drier.



P. pungens ‘Hoopsii’ - image: Floramedia

P. abies is the most well-known tree but may not be the most attractive species if you are only planting one specimen tree. If you are planting a single specimen in a park or garden, you should choose between P. smithiana, P. breweriana AGM, P. omorika AGM, P. pungens and P. orientalis AGM. They like an open but sheltered position, without being overshadowed by other trees. 

Choose trees grown from seed, not grafted ones. P. pungens provides that incredible silvery blue colouring, which earns it the name "Colorado blue spruce". It is a great alternative to the traditional Christmas tree. 

As mentioned, there are many dwarf cultivars that remain popular — varieties of P. abies, P. glauca and P. orientalis AGM in particular. For example, P. abies ‘Little Gem’ AGM is a popular choice as a rock garden plant because of its compact, globose form and how the new needles in spring show bright green against the older dark-green needles. 

Another is P. glauca var. albertiana ‘Conica’ AGM, a dwarf conical form that has light-green needles at first that turn a light bluish-green later.

One of the worst pests for spruce is the widespread green spruce aphid, which can cause severe defoliation of several species, particularly when in warm areas following mild winters. Red spider mite and the conifer spinning mite can also be problems. Spruce gall adelgids can create pineapple-shaped galls. 

What the specialists say

Robert Williamson, head of conifer department, Ashwood Nurseries, West Midlands

"Picea are excellent specimen trees, particularly the dwarf varieties of P. glauca and P. orientalis. They prefer an acid soil and pests to watch out for include the spruce aphid and red spider mite. 

"The species or varieties that stand out for me include varieties of P. glauca such as ‘Sanders Blue’, ‘Maygold’, var. albertiana ‘Conica’ and var. albertiana ‘Alberta Globe’. 

"‘Sanders Blue’ is a slow-growing conical tree that has fantastic silvery-blue needles. It is popular as a small potted tabletop Christmas tree, but after that use it can be transferred to a patio pot and then be planted outside, where it can reach 4-6m tall. 

"Nice P. orientalis varieties include ‘Tom Thumb Gold’, with its lovely bright gold colour, and one of the smallest of the Picea, ‘Professor Langner’, which forms a dense miniature bun with small, thin, emerald-green needles."

In practice

Tony Kirkham, arboretum head, Royal Botanic Gardens, Kew

"Picea species are finding it hard with the climate in the south of England. P. sitchensis and P. abies need more rain and a cold winter, so they generally look tired in the garden, as do most of the Asian species apart from P. smithiana, which is a most beautiful tree. Both P. orientalis and P. pungens as well as the cultivar ‘Glauca’, on the other hand, do well and relish the hotter drier summers, retaining all of their needles for several years and looking healthy.

"P. omorika is one of my favourites, which appear to be doing well with their very narrow columnar habit. P. breweriana is a very graceful looking tree with its broad spreading pendulous form. 

"All the spruces grown as specimen trees in a collection or garden need a good soil to do well, not chalk, and must be planted with some protection from winds unless they are being used for forestry or woodland planting on a large scale.

"I would plant smaller sized specimens — up to 1m high — rather than trying to establish semi-mature specimens. Retain the lower skirt to the ground and develop and retain it within a mulched circle rather than cleaning up the trunk as a standard."

Species and varieties

P. abies is the Norway spruce, highly recognisable as the traditional Christmas tree. It has an attractive pyramidal shape when young, gradually becoming more columnar with age, and bears numerous large, slender, reddish-brown cones. 
Fast-growing, it is widely produced commercially, not only as a Christmas crop but for its timber, used in the construction industry, and for wood pulp. Height: 25-40m.

P. abies ‘Little Gem’ AGM (H7) is a very slow-growing conifer, forming a squat, globose bun with short, dense, dark-green needle-like leaves. The new growth in spring is a brighter green. Ideal as a rock garden specimen. Height and spread: 30cm.
P. abies ‘Nidiformis’ AGM (H7) is a dwarf shrub that forms a low flattopped mound of dense needles that begin a fresh green in the springtime and turn olive green during the summer. Height: 1-1.5m. Spread: 2.5-4m.

P. breweriana AGM (H6), the Brewer’s weeping spruce, is a medium-sized tree of broadly conical habit. Its distinctive feature is its drooping curtains of dark-green foliage. Looks great as a specimen plant in large gardens. Produces purple and brown cones. Very slow-growing, typically growing less than 20cm per year. Height: 12m-plus. Spread: 2.5-4m.

P. glauca var. albertiana ‘Alberta Globe’ AGM (H7) is a slow-growing dwarf conifer, forming a neat mound of tightly knit, sea-green needles. Height and spread: 50cm-1m.
P. glauca var. albertiana ‘Conica’ AGM (H7) is a dwarf evergreen conifer with a neat, conical shape and light-green needles that turn light bluish-green later. It can be grown as either a specimen tree in a small garden or used when very young as a tabletop tree at Christmas time. Height: 4m. Spread: 3m.

P. omorika AGM (H7), the Serbian spruce, has a very slender, tapering and elegant form and dark-green needles. An alternative to the traditional Christmas tree. Copes with a variety of soils. Height: 30m.

P. orientalis AGM (H7) is a large tree of dense, conical habit with dark, shining green, needle-like leaves. Produces purple cones. Height: 12m. Spread: 4-8m.

P. pungens (Glauca Group) ‘Hoopsii’ AGM (H7), the Colorado blue spruce, is a small evergreen tree with long, thick, silver-blue needles that make it an exceptional specimen tree. It has a pyramidal form and is an alternative choice for Christmas trees. Height: 10m. Spread: 5m.

P. sitchensis, the Sitka spruce, is commonly seen growing in plantations, where it is harvested for its timber. It was introduced to Britain in 1831 and does well in the north and west of the UK on the moist but well-drained soils that it needs. Height: 60m.

P. smithiana has distinctive elegant hanging branches with a gracefully weeping tip. Its needles are bright green and the longest of any spruce. Also bears long narrow brown cones. Can be vulnerable to late-spring frost as a young plant. Height: 20m. Spread: 15m.

Thank you to Floramedia, which supplied the images for this article from its photo library www.floramedia-picture-library.com


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