There is an impressive quantity of conifer cultivars with more or less blue foliage. Here is a selection of the best forms that are offered by nurserymen.
Cedars (Cedrus)
Dwarf forms are quite rare in this category of conifers and always very original. The Himalayan cedar (Cedrus deodara) has a dwarf form with silvery blue foliage, 'Feeling Blue'. It is a slow-growing creeping cedar, ideal for planting in containers or rock gardens, or even to cover the ridge of a low wall. Adult height 80 cm, width 3m.
Spruces (Picea)
This category includes conifers with a really intense blue color.
The dwarf Colorado spruce, Picea pungens 'Glauca Globosa' is commonly called "dwarf blue fir". It is the most common cultivar, and one of the best varieties for small gardens and container growing. It forms a nice compact ball, which evolves into a rounded pyramid that can reach 2 m high at 30 years. The average annual growth is 6 to 8 cm. The short and tight needles, prickly, keep a beautiful silver-blue color all year long.
Among the Picea pungens, there are other dwarf forms such as 'Glauca Procumbens', totally spread out, to be grown with golden heather. 'Prostrata' is a closely related cultivar that does not exceed 60 cm in height, but can spread over 2 m wide.
The white fir (Picea glauca) has given some dwarf and bluish forms like: Picea glauca 'Echiniformis', which forms a spreading cousin of 50 cm high at adulthood, with needles of a greyish glaucous green. Picea glauca 'Sanders Blue' forms a cone about 50 cm high at 15 years old, with very pretty blue young shoots.
False cypress (Chamaecyparis)
Blue forms are rarer in the dwarf than in the taller varieties.
Chamaecyparis pisifera 'Boulevard' forms a compact pyramid with silvery-blue young foliage, reaching 3 m high in 15 years. This conifer grows very well in a container and can tolerate part shade. 'Squarrosa Lombarts' has very fine foliage, soft to the touch, which turns bluish to purple in autumn. It forms a flattened sphere of 1.50 m high at 20 years.
Juniper (Juniperus)
There are many blue spreading forms among the junipers, many of which have fine needles that are quite prickly.
The common juniper comes in several blue forms, including 'Blue Chip' (or 'Blue Moon'), with a spreading habit, of a steel blue that turns purplish purple in winter, it does not exceed 30 cm in height, for 1 m wide; and 'Wiltonnii', totally prostrate, of a pretty steel blue with very fine foliage, which turns purplish in winter. It spreads over 2 m. These are very resistant conifers that can withstand both cold and heat.
The Chinese juniper (Juniperus chinensis) has a very beautiful glaucous blue cultivar, 'Blue Alps', which forms a bushy erect bush of irregular appearance.
The scaly juniper (Juniperus squamata) in its 'Blue Carpet' form is very prostrate, with short shoots of bright silvery blue foliage. Perfectly hardy, it can be pruned. It does not exceed 50 cm in height, but spreads over 1.50 m. 'Blue Star' is more compact, in the shape of a spiky ball of a very bright blue. It tolerates limestone, but grows very slowly, which makes it recommended for pots. Maximum height: 1 m. 'Meyeri' has obliquely spreading branches of a steel blue that turn purple in winter. It can reach 2.50 m high, doing well in limestone soil.
The beach juniper (Juniperus conferta), exists in a form with blue-gray foliage 'Blue Pacific', a creeping conifer whose branches lie on the ground, or fall down in cascade when it is cultivated in pot. It tolerates drought and calcareous soils. Its color is more intense in the sun.
The sabina juniper (Juniperus sabina) is naturally glaucous, a color accentuated in the cultivar 'Blue Danube', a plant with a very spread out habit, whose foliage has bluish gray reflections.
Firs (Abies)
Dwarf and blue forms are quite rare in the genus Abies.
The Colorado Blue Fir (Abies concolor) has bluish-green needles. 'Archer's Dwarf' is an American cultivar with glaucous foliage and slow growth, to be grown in rock gardens. Compacta', with greyish steel blue needles is more common, characterized by an irregular silhouette. It can grow to over 2 m in height.
The Greek fir (Abies cephalonica) has produced some slightly bluish cultivars. Meyer's Dwarf' (or 'Nana') grows horizontally.
The mountain fir (Abies lasiocarpa) produces a dwarf form of a superb bluish-gray 'Compacta' (sometimes wrongly called Abies arizonica 'Compacta') which forms a nice regular pyramid, very tightly packed. This cultivar grows to over 2 m tall as a mature tree and is drought resistant, but does not appreciate limestone.
The California red fir (Abies magnifica) has a rare 'Nana' form, which consists of an irregular stack of bluish swatches.
Spanish fir (Abies pinsapo) mixes green and bluish twigs in the cultivar 'Horstmann Witches', which takes a spreading, rather irregular form.
The noble fir (Abies procera) exists in a very dwarf form 'Blaue Hexe', a compact ball, native to Germany, to be grown mostly in pots.
Blue conifer FAQ
How to avoid sudden browning?
When it occurs in hot, dry weather, this phenomenon is due to an attack of red spiders. This is the number one enemy of blue conifers. A systematic preventive treatment with a specific acaricide (based on dicofol or cyhexatin) is recommended, as soon as the climatic conditions are favorable to the development of mites.
In cool and rainy weather, it is more likely to be conifer dieback (Phytophthora cinnamomi). This rapidly fatal disease is more frequent in containers. It affects young plants more strongly. Aliette is the only effective preventive product against this fungus that develops in the soil.
Why is a green branch growing on my blue conifer?
This is a phenomenon of reversion that is frequently observed in plants with colored or variegated foliage, but also in double flowers, which become single again. It is simply a return to the original type. You should remove the green part very quickly, as it always has a higher vigor than the colored shoots. In grafted trees, the rootstock can also be freed, with the emission of vigorous shoots (gourmands).
Are blue conifers resistant to cold?
Yes, they are. Frosts of -10°C and even -15°C have no effect on these plants. However, young trees should not be exposed to cold winds for the first five years after planting. A mulch of pine bark will also play a protective role for the roots against heavy frosts, especially for plants in containers.
The garden of the curious and the botanist
- Picea pungens was discovered in Colorado in 1862 by Dr. C. Parry. It is the cultivar 'Glauca Koster', obtained in 1885 by the Dutchman Arie Koster, which is today the most popular blue fir. It reaches 15 m in height.
- The true name of "blue fir" should be reserved for Abies procera, also called "noble fir", native to the mountains of Oregon, where it was discovered in 1825 by David Douglas
- Permanent mulching with light blonde flax chaff highlights the blue foliage of the conifer, while reducing watering and weed growth.
- The somewhat unchanging appearance of evergreens can become monotonous if they are too dominant in the garden. Do not exceed 50% conifers in the composition of a bed, the reasonable proportion being rather one third.
- Many blue conifers (especially in dwarf forms) are propagated by grafting. This, together with their slow growth, explains and justifies their relatively high price.
- The needles of conifers that fall as the foliage regenerates, acidify the soil. It is therefore advisable to lime (a handful of slaked lime per square meter) every two years or so.
