Foliage and ripe pollen cones on a plant at the Arnold Arboretum, Massachusetts, USA [©Bob Mayer, 2016.05.06].


Valid HTML 4.01 Transitional

Abies × borisii-regis

Mattfeld 1925

Common names

King Boris Fir, Bulgarian Fir, Macedonian Fir; Българска ела [Bulgarian]; makedón jegenyefenyő [Hungarian].

Taxonomic Notes

Synonymy (Farjon 2010):

Type locality in the Rodopi Mts about 50 km SW of Plovdiv, Bulgaria (Liu 1971).

Since the analysis by Liu (1971), this species is generally regarded as of hybrid origin, originating from introgression between A. alba and A. cephalonica. This hybrid origin has been conclusively shown by Bella et al. (2014) "using paternally inherited (chloroplast) and maternally inherited (mitochondrial) DNA markers. Both silver and Greek fir could be clearly distinguished using mitochondrial markers, while [they] observed a mixture of maternal lineages in the A. × borisii-regis populations." The chloroplast data also supported the conclusion of a hybrid origin for the species. As detailed by Mitsopoulos and Panetsos (1987), A. alba periodically introgressed populations of A. cephalonica in the southern Balkans during north/south migrations associated with Pleistocene glaciations, with two consequences: development of true-breeding hybrid populations, and restriction of pure A. cephalonica to a few refugia in southern Greece (Farjon 2010). Rushforth (1987) considers that it is "better understood as part of the group from which all these species [European and SW Asian Abies] have separated" rather than a recent hybrid; this view is supported by the presence of trees in the wild in Bulgaria with some foliage characters resembling A. nordmanniana (Frankis 2001).


Trees to 40 m tall and 150 cm DBH, with a single straight round trunk and whorls of horizontal primary branches forming a conical crown that becomes flattened in old trees. Bark first gray and smooth, with age darker, scaly and fissured. Twigs slender, flexible (stouter on cone-bearing twigs), yellow-gray, striated with short yellow or brown pubescence; leaf scars nearly circular. Vegetative buds ca. 6 × 4 mm, not resinous. Leaves spirally arranged, in shade foliage appearing 2-ranked, 15-30 × 1.5-2.6 mm, linear, grooved and dark green above, with two pale green stomatal bands flanking a midrib below, apex entire. Pollen cones lateral, crowded along the shoot, ca. 20 mm long, greenish yellow with purple-red microsporophylls. Seed cones lateral, erect, cylindrical with conical to obtuse apex, 10-15 × 3-5 cm, yellow-green ripening to brown, with a persistent dark brown rachis. Seed scales cyathiform, 25-30 × 25-30 mm at mid-cone, smooth, outer margin entire; linear bracts with a long cusp, up to 4 cm long, exserted, slightly recurved. Seeds angular, 7-9 mm long with a 10-15 mm reddish yellow wing (Vidakovic 1991, Frankis 2001, Farjon 2010).

Overall, the species is very similar to Abies alba, with which it often occurs; the principal distinction is that A. alba has no stomata on the upper leaf surface and generally has an emarginate leaf apex, while A. borisii-regis occasionally (especially on sun foliage) bears stomata on the distal, upper surface of the leaf, and does not have an emarginate leaf apex (Farjon 2010).

Pietro Paolo Adinolfi (e-mail 1998.01.11) reports: "Some months ago I met Dr. Arsen Proko from Tirana University. ... This abies has a particular character which isn't in Abies alba and in Abies cephalonica. If you cut a tree there will be suckers [perhaps sprouts?] from the stump."

Distribution and Ecology

Albania, Bulgaria, and Greece (see map below). It primarily occurs in montane forest at 700 to 1500 m elevation, often in pure stands or with Picea abies, or mixed with broadleaf species at lower elevations within its range (Farjon 2010). Hardy to Zone 6 (cold hardiness limit between -23.2°C and -17.8°C) (Bannister and Neuner 2001).

Distribution of Abies in the Mediterranean region. Data from Conifers of the World BRAHMS database, downloaded 2017.11.05, and from Pasho et al. (2014). Taxa are color coded; see pull-out menu at left of map for details. Click on each occurrence for further information.

Big tree


A tree-ring chronology covering 170 years, presumably based on living tree material, was collected in 1996 at Panetolikon-Oro, Greece (1350 m elevation, 38° 43'N, 21° 40' E) by F.H. Schweingruber (NOAA 1999). Very few collections of this species are recorded and substantially older trees may occur.


Limited work has been done. A 2014 study evaluated climate-ring width relationships in trees from southeast Albania, and unsurprisingly found a sensitivity to summer drought (Pasho et al. 2014).


The timber is used for plywood and interior construction, much as is A. alba (Farjon 2010). It is also a moderately popular horticultural species.


Pasho et al. (2014) report collections in the southwestern part of National Park Bredhi i Hotovës in Albania (which translates as "Firs of Hotovna National Park"); collection sites, shown on the map above, appear to be readily accessible from the nearby road. The map above also shows some recent collections (1985, 2006) in the Rila Mountains of Bulgaria; both appear to be accessible from Highway 107 and the Rila Monastery (a popular attraction). There also appear to be a number of recent collections from northern Greece, particularly in the Pierian Mountains.


Named in honor of Tsar Boris III of Bulgaria (1894-1943, King of Bulgaria 1918-1943).


Bella, E., S. Liepelt, L. Parducci and A. D. Drouzas. 2014. Genetic insights into the hybrid origin of Abies × borisii-regis Mattf. Plant Syst Evol DOI 10.1007/s00606-014-1113-x.

Frankis, M.P. 2001. Field notes, Bulgaria, September 1998 and September 2001.

Mattfeld, J. 1925. Die in Europa und dem Mittelmeergebiet wildwachsenden Tannen. Mitt. Deutsch. Dendrol. Ges. 35: 1-37, f. 1-10; p. 235.

Mitsopoulos, D.J., and C.P. Panetsos. 1987. Origin of variation in fir forests of Greece. Silvae Genetica 36(1):1-15.

NOAA Paleoclimatology Program Tree-Ring Data Search Page. 1999.02.24. Results of database search. URL:

Pasho, Edmond, Elvin Toromani and Arben Q. Alla. 2014. Climatic impact on tree-ring widths in Abies borisii-regis forests from South-East Albania. Dendrochronologia 32:237-244.

Thanks to Michael Frankis for extensive revisions to this page, 2002.01.

See also

Roussakova [n.d.], accessed 2017.12.26.

Last Modified 2018-01-19