Baileya 23(2), pp. 57-67. 1989.
Identification of the Heath-Leaved Cypress,
Chamaecyparis thyoides ‘Ericoides’ (Cupressaceae)
Regis B. Miller
Center for Wood Anatomy Research, USDA Forest Service,
Forest Products Laboratory, One Gifford Pinchot Dr.,
Madison, Wisconsin 53705-2398
AND
Frederick G. Meyer
USDA, Agricultural Research Service, U. S. National Arboretum,
3501 New York Ave., N. E., Washington, D.C. 20002
A BSTRACT . Cultivated forms of conifers with juvenile leaves pose
problems of identification that are not easily reconciled by conventional
methods. The wood from a specimen of the heath-leaved cypress
(Chamaecyparis thyoides ‘Ericoides’) was examined to correctly identify
this juvenile-leaved cultivar. The nomenclatural history and
identification have been much confused and remained unresolved for
well over a century. Comparing the macroscopic and microscopic wood
anatomical features of the cultivar to all coniferous genera, particularly
to the species of Chamaecyparis and Thuja, we found that the
heath-leaved cypress is C. thyoides. The taxonomic, nomenclatural, and
historical aspects of this cultivar are also reviewed.
Since its introduction to cultivation more than a century ago, the taxonomic
and nomenclatural history of the heath-leaved cypress (a juvenile form of
Chamaecyparis thyoides (L.) BSP.) has been much confused. Lacking the more
distinctive adult leaves, conifers with only juvenile leaves often are difficult to
identify. Chamaecyparis thyoides is an indigenous conifer of coastal eastern
United States. This attractive, small, columnar tree, with summer gray-green
leaves that turn shades of copper or purple in winter, is often planted in parks
and gardens, and not uncommonly in cemeteries, primarily in parts of the
southeastern United States. The heath-leaved cypress is well known to the
second author from the voucher collections documented from many sites in the
southeastern United States over the past 20 years. Nurserymen know this plant
and still grow it to a limited extent, but the identity of this juvenile form has never
been established with certainty until now. Recent nursery catalogues have listed
it as Retinospora ericoides, a name without botanical standing. In an attempt to
resolve the taxonomic and nomenclatural dilemma of this conifer, we turned to
another avenue of investigation, namely wood anatomy. It is well known that
anatomical features of the wood have diagnostic value in the generic identification of conifers (Phillips, 1948; Greguess, 1955 Kukachka, 1960).
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HISTORICAL RÉSUMÉ
The heath-leaved cypress was first offered in the United States by the
Fruitland Nursery of Augusta, Georgia, in their 1857–1858 catalog, as Cupressus
ericoides, a name without botanical standing. The nursery listed it under this
name year after year at least up to 1900. However, it has been offered by other
nurseries since that time. The brief description of this conifer in the Fruitland
Nursery Catalogue for 1872 leaves little doubt that it is the same plant we discuss
in this paper: "Heath leaved, very compact, foliage very distinct, turning purple
in winter, a desirable plant of moderate growth." The proprietor of the Fruitland Nursery, P. J. A. Berckmans, was a Belgian immigrant actively engaged in
introducing nursery plants from Europe to grow in his Georgia nursery. For
this reason, we are confident that the heath-leaved cypress was one of the plants
introduced by Berckmans. The origin of the selection ‘Ericoides’ in Europe was
most likely as a branch sport of Chamaecyparis thyoides. Den Ouden and Boom
(1965) indicated the year 1840 as the original date of introduction for C. thyoides
‘Ericoides’ by a nursery in France. The European introduction date of 1840 was
derived from a reference by Carrière (1867) related only to the introduction of
Retinospora pseudosquarrosa, which Carrière said was "Obtenu au Mans, vers
1840 par M. Bergeot." The plant in question surely was not the heath-leaved
cypress, but more likely a variant of Chamaecyparis pisifera (Sieb. & Zucc.)
Endl. ‘Squarrosa’, a well-known juvenile-leaved cultivar of Japanese origin. As
we explain later in this section, the place and date of origin of this conifer in
Europe cannot be established with certainty. However, Loudon (1838)
recorded that C. thyoides was first introduced to Europe in 1736.
Since authenticated voucher specimens are not available for validation of
the many names that have been proposed for the heath-leaved cypress, it is
nearly impossible to typify most of the names listed by Rehder (1949) and others
who have dealt with this conifer. Since 1850, the heath-leaved cypress has been
assigned to no fewer than six genera of coniferous plants, namely Widdringtonia,
Chamaecyparis, Cupressus, Retinospora, Juniperus, and Frenela. The name
Widdringtonia ericoides of Knight (1850), which appeared without a description
in a nursery list, should be excluded from further consideration. Carrière (1855)
proposed the name Chamaecyparis ericoides and listed the earlier name, Widdringtonia ericoides of Knight and Perry, as a synonym. Later, Carrière (1867)
listed both C. ericoides and W. ericoides as synonyms of Retinospora squarrosa
Sieb. & Zucc. The latter name is now treated as a synonym of Chamaecyparis
pisifera ‘Squarrosa’. According to Gordon (1858, 1875), Retinospora ericoides,
listed by Carrière (1855), was a plant "cultivated by the Japanese in pots, under
the name of Nezu (dwarf)," or as Nezu-hiba (dwarf tree of life) (Gordon, 1862).
Veitch (1881) refuted Gordon’s incorrect assertion that Retinospora ericoides
was of Japanese origin; Veitch’s view was accepted by later authors. However,
Welch (1979) again supported the notion of a Japanese origin for the heathleaved cypress, merely repeating Gordon’s incorrect assertion of 1858. The
evidence presented here shows clearly that the cultivar ‘Ericoides’ belongs with
an American species, Chamaecyparis thyoides, and not with either of the
Japanese species, C. obtusa (Seib. & Zucc.) Endl. or C. pisifera.
JULY 1989
MILLER & MEYER HEATH-LEAVED CYPRESS
59
Beissner (1880) was the earliest author to apply the name Chamaecyparis
sphaeroidea (Sprengel) Spach var. ericoides Beissn. & Hochst. to the heathleaved cypress. According to modern usage, the specific epithet sphaeroidea
has been replaced by the older thyoides, and the horticultural variety ericoides
should now be cited as a cultivar, ‘Ericoides’. At the same time that he applied
the name C. sphaeroidea, Beissner treated Frenela ericoides hort. and Juniperus
ericoides hort. as synonyms. Later, Sudworth (1897) listed the heath-leaved
cypress as Chamaecyparis thyoides ericoides (Knight) Sudworth. More recent
authors, including Bailey (1923, 1933), Dallimore and Jackson (1931, 1948,
1966), Den Ouden (1949), Den Ouden and Boom (1965), and Welch (1966)
follow the nomenclature of Beissner and of Sudworth. Krüssmann (1972),
unfortunately, accepted the earlier erroneous statement of Den Ouden and
Boom (1965) that the heath-leaved cypress was of French origin, dating from
1840.
MATERIALS AND METHODS
The wood sample for this study, now identified as Chamaecyparis thyoides
‘Ericoides’, was provided by Daniel B. Ward, Department of Botany, University
of Florida Gainesville, Florida. The sample, consisting of heartwood, sapwood,
and bark, was obtained from a large old tree on the campus of the University
of Florida. This sample was accessioned into the wood collection at the Forest
Products Laboratory and numbered as MADw 42516. For comparison, various
species and genera from the Madison (MADw) and S. J. Record (SJRw) wood
collections were examined.
Permanent microscope slides of the wood were prepared according to
standard techniques. Two slides were stained with safranin, and two were
unstained. Maceration were made using 50/50 hydrogen peroxide-acetic acid,
mounted in a 50/50 glycerol-alcohol solution, and left unstained.
Terminology follows the IAWA Committee on Nomenclature (1964).
Anatomical features observed and described generally follow standard practices for coniferous woods (Phillips, 1948; Kukachka, 1960). Tracheid length
and ray height are based on 100 randomly selected measurements; the tangential diameter of tracheids and the number of rays per tangential mm2 are based
on 50 measurements.
RESULTS
Description of the wood sample; Heartwood light brown or tan with a slight
reddish cast, distinct from the light tan or cream sapwood. Wood with a
characteristic aromatic or “cedar” odor, but no greasy feel, distinctive taste, or
dimpled grain. Growth rings distinct to somewhat indistinct, 2-6 mm wide;
transition from earlywood to latewood gradual (Fig. 1). Tracheid length 2.20
(1.68-2.74) mm; earlywood tracheids 24 (16-32) µm and latewood tracheids 24
(14-30) µm in tangential diameter; one row of bordered pits on radial walls
(Fig. 2), tangential pits scattered, only occasionally present; spiral thickenings
absent. Cross-field pitting typically cupressoid, especially on the first several
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rows of earlywood tracheids, somewhat taxodioid to cupressoid on latewood
tracheids. Axial parenchyma abundant (Fig. 1), end walls smooth to slightly
nodular as viewed on the tangential section (Fig. 3); cell contents brown to
yellowish or reddish brown. Rays uniseriate to rarely biseriate in part, 8.7 (l-26)
cells high, but mostly 5-14 cells high or 291 (157-444) µm high; 60.8 (44-81) per
tangential mm2 (Fig. 3). Ray parenchyma with smooth end walls (Fig. 4), not
indentured cell contents occasionally brown to yellowish or reddish brown.
Ray tracheids absent (Fig. 2). Axial and horizontal resin ducts absent (Fig. 1).
Crystals absent.
DISCUSSION AND CONCLUSIONS
A comparison of the macroscopic and microscopic wood anatomical features of the heath-leaved cypress with those of other coniferous genera, in
particular with species of Chamaecyparis and Thuja, confirmed that this
juvenile-leaved form is correctly identified as Chamaecyparis thyoides (L.) BSP.
‘Ericoides’. We reached this conclusion using the keys, tables, and descriptions
of Kukachka (1960) and Phillips (1948), and comparing the heath-leaved
cypress to known wood specimens in MADw and SJRw.
Kukachka (1960) studied fifteen coniferous genera from North America and
three from Asia and South America. He constructed an identification table of
all the distinct species, species groups, and genera, The wood of the heathleaved cypress lacks resin canals, spiral thickenings, and ray tracheids, and it
has only a single row of bordered pits on the axial tracheids (Fig. 2). In addition,
the end walls of the ray parenchyma cells are smooth (Fig. 4). Following
Kukachka (1960), this set of features eliminates all taxa except Thuja,
Chamaecyparis (not including C. nootkatensis (D. Don) Spach, which has ray
tracheids) and Cupressus lusitanica Miller. All American species of Juniperus
(one of the six genera to which ‘Ericoides’ has been assigned) have distinct
nodular ray parenchyma end walls that could not be mistaken for the smooth
end walls observed in the heath-leaved cypress. Furthermore, the junipers
generally have characteristic heartwood color and odor, which were not observed in the heath-leaved cypress.
Of the species remaining, Thuja has indentures and taxodioid cross-field
pitting, whereas the heath-leaved cypress lacks indentures and cupressoid
cross-field pitting. The remaining species in Kukachka’s (1960) table are
Cupressus lusitanica, Chamaecyparis lawsoniana (A. Murr.) Parl., and
+
Figures 1-4. Chamaecyparis thyoides ‘Ericoides’ (MADw 42516). 1. Crosssection showing gradual transition between earlywood and latewood, lack of
resin ducts, and abundance of axial parenchyma (dark cells, see arrows). 16×.
2. Radial section showing a single row of bordered pits on the axial tracheids
and the lack of ray tracheids. 200×. 3. Tangential section showing uniseriate
rays and smooth end walls (arrows) in the axial parenchyma cells. 200×.
4. Radial section showing smooth end walls (arrows) in the ray parenchyma
cells. 500×.
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C. thyoides. The critical feature separating these species is the presence or
absence of nodular end walls on the axial parenchyma. Cupressus lusitanica and
Chamaecyparis lawsoniana have nodular end walls on the vertical parenchyma;
Chamaecyparis thyoides has smooth end walls, as does the heath-leaved cypress
(Fig. 3).
Phillips (1948) studied species from 41 coniferous genera throughout the
world, and constructed an identification table. A comparison of the wood
anatomical features of the heath-leaved cypress with Phillips’ table produced
nearly the same results as that with Kukachka’s table. The lack of resin ducts,
ray tracheids, and spiral thickenings, coupled with the presence of smooth end
walls on the ray parenchyma, a single row of bordered pits on the axial tracheids,
and an abundance of axial parenchyma, eliminated many of the genera. A
characteristic odor, distinct growth rings, and light brown heartwood of the
heath-leaved cypress eliminate all other conifers except Chamaecyparis (except
C. nootkatensis), Cupressus sempervirens L. and Cupressus torulosa D. Don
and Libocedrus tetragona (Hook.) Endl. (syn. Pilogerodendron uvifera (D. Don)
Florin). The lack of indentures eliminates the two species of Cupressus, and the
presence of smooth end walls on the axial parenchyma eliminates the species
of Libocedrus, Chamaecyparis lawsoniana, and Chamaecyparis obtusa, leaving
only Chamaecyparis thyoides.
In the final analysis, attention was concentrated on wood specimens from
both MADw and SJRw of the genera Chamaecyparis and Thuja. Anatomically,
Thuja is somewhat similar to the heath-leaved cypress, but according to Kukachka (1960), Phillips (1948), Jacquoit (1955), and Greguess (1955), most species
have taxodioid cross-field pitting, indentures, and nodular end walls on the axial
parenchyma. These features separate Thuja from the cultivar ‘Ericoides’, but
sometimes the features are not easily discerned. Additional, more easily recognized features are odor, heartwood color, abundance of axial parenchyma, and
the color of the ray cell contents. All these features suggest that the cultivar
‘Ericoides’ is not a species of Thuja.
For Chamaecyparis, a comparison was made of wood specimens and microscope slides of the following C. nootkatensis, C. lawsoniana, and C. thyoides
from North America and C. obtusa and C. pisifera from Asia. Of these five
species, all except C. nootkatensis lack ray tracheids, none of which were
observed in the cultivar ‘Ericoides’. In addition, the heartwood of C. nootkatensis has a very characteristic odor resembling that of raw potatoes.
Chamaecyparis lawsoniana, C. obtusa, and C. pisifera have nodular end walls on
the axial parenchyma cells, and the yellowish white to very pale brown
heartwood is strongly aromatic with a pungent, ginger-like odor. When compared side by side, the heartwood of C. thyoides is darker brown, and the odor
different, more aromatic or “cedar-like”. The critical feature separating
C. thyoides from the other three species of Chamaecyparis is the presence of
smooth end walls on the axial parenchyma cells. Thus, the features of
C. thyoides match those of the heath-leaved cypress.
JULY 1989
MILLER & MYER: HEATH-LEAVED CYPRESS
63
TAXONOMY AND NOMENCLATURE
Chamaecyparis thyoides (L.) BSP. ‘Ericoides’
Clonotype: U.S.A. District of Columbia: U.S. National Arboretum,
F. G. Meyer s.n., NA 29903 (isoclonotypes: A, BH).
Summary of published combinations and authorities that refer to this cultivar:
Widdringtonia ericoides J. Knight, Syn. conif., pl. 13.1850.
Chamaecyparis ericoides Carrière, Traité gén. conif. 140. 1855.
Retinospora ericoides Zucc. ex Gordon, Pinet. Suppl. 91.1858.
Cupressus ericoides hort. ex Gordon, Pinet. Suppl. 91.1862.
Thuja ericoides hort. ex Gordon, Pinet. Suppl. 91.1862.
Retinospora obtusa Siebold var. ericoides Hoopes, Book evergr. 358.1868.
Chamaecyparis sphaeroidea (Sprengel) Spach var. ericoides Beissner &
Hochstetter ex Beissner, Gartenflora 29:364.1880.
Frenela ericoides hort. ex Beissner, Gartenflora 29:364.1880.
Juniperus ericoides Nois. ex Beissner, Gartenflora 29:364.1880.
Cupressus thyoides ericoides C. S. Sargent, Silva 10112. 1896.
Chamaecyparis thyoides ericoides (J. Knight) Sudworth, U.S.D.A. Div.
Forest. Bull. 14:79.1897.
Chamaecyparis thyoides (L.) BSP. var. ericoides (Beissner) Dallimore &
Jackson, Hand. Conif. 222.1931.
Chamaecyparis thyoides f. ericoides (Carrière) Rehder, Bibl. cult. trees and
shrubs 51.1949.
Evergreen shrub or tree, sterile, up to 10 m tall, narrowly columnar to
pyramidal, with one to several trunks, much branched, the branchlets dense and
crowded; leaves juvenile, crowded, soft to the touch, decussate or ternate,
linear, 3.5-8.0 mm long, 0.75-1.00 mm wide, flat, with an abrupt point, with two
white stomatic bands beneath; previous year’s leaves gray-green, current
season’s leaves blue-green, turning shades of copper to purple in winter, with a
slight resinous odor when crushed (Figs. 5 and 6).
O THER S PECIMENS E XAMINED . U.S.A. Alabama: Mobile Co.: Mobile,
hwy. 98, Scenic Motel, F G. Meyer & P. M. Mazzeo 10528 (A, NA). Florida:
Alachua Co.: Gainesville, Univ. of Florida, Royal James Wilmat Gardens,
F. G. Meyer & P. M. Mazzeo 13413 (NA); Baker Co.: Glen St. Mary, Glen St.
Mary Nursery, F. G. Meyer & P. M. Mazzeo 10701 (NA); Leon Co.: Alfred B.
Maclay Gardens State Park, F. G. Meyer & P. M. Mazzeo 10617 (A, NA); Nassau
Co.: Rte. 17, Riverside Motel, F. G. Meyer & P. M. Mazzeo 13562 (NA). Georgia: Chatham Co.: Savannah, Bonaventure Cemetery, F. G. Meyer 10283 (NA);
Cherokee Co.: Canton, Rte. 140, Garden of Eugene Cline, F. G. Meyer &
P. M. Mazzeo 20577 (NA). Maryland: Montgomery Co.: Wheaton, Brookside
Gardens, F. G. Meyer 21937 (NA). Massachusetts: Suffolk Co.: Jamaica Plain,
Arnold Arboretum, L. H. Bailey s.n., 30 Oct 1921 & 17 Oct 1932 (BH); R. Warren 120 (BH). North Carolina: Craven Co.: New Bern, Tyron Palace, F. G. Meyer
16400 (NA). Pennsylvania: Philadelphia Co.: Germantown, Hort. Meehan,
T. Meehan s.n, 1900 (A). South Carolina Charleston Co.: Charleston, Old
Town, Garden of Ferdinanda Waring, F. G. Meyer & P. M. Mazzeo 13684 (NA);
Dorchester Co.: Rte. 17 (alt,) near Summerville, F. G. Meyer 15354 (NA),
Viginia: Henrico Co,: Richmond, 6311 Three Chopt Rd., Garden of Tom
Wheeldon, F. G. Meyer & P. M. Mazzeo 14741 (NA). G ERMANY . Breslau,
Scheitniger Park, C. Baenitz s.n., 15 Jul 1902 (A), 23 Oct 1909 (BH). ENGLAND .
Berkshire: Windsor, Windsor Great Park, J. D. Bond s.n., 15 Sep 1987; Surrey:
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Kew, Royal Botanic Gardens, G. Nicholson s.n., 10 Mar 1880 (A); Wiltshire:
Davizes, Nursery of H. J. Welch, D. H. Hunt s.n., 27 Oct 1967 (NA). NETHERLANDS . Schovenhorst, Putten, J. V. Suringar s.n., Jul 1910 (WAG).
The cultivar ‘Ericoides’ conforms with the ICNCP, 1980, Art. 27, as a name
that had been in existence before 1 January 1959, and is therefore valid in its
Latin form. Designation of a clonotype was essential to fix the name
Chamaecyparis thyoides ‘Ericoides’ with a permanent voucher specimen for
purposes of referenee.
Editor’s note: The term "clonotype" is not sanctioned by the International
Code of Nomenclature of Cultivated Plants, but it is widely employed in the
literature of cultivar names.
ACKNOWLEDGMENTS . This joint study was initiated as a result of our discussion
with Dr. Daniel B. Ward in Gainesville, Florida, in 1985, and the very ample
wood sample of the heath-leaved cypress he kindly donated at that time. Also,
we kindly thank Dr. John D. Bond, of Windsor Great Park, Windsor, Berkshire,
England, for sending living material for comparison with the heath-leaved
cypress cultivated in the United States. This and other material of European
origin cited under Specimens Examined have aided greatly in the identification
of this plant, at the same time confirming the identity of this conifer in Europe
as the same cultivar grown in the United States. The drawing for Figure 6 was
prepared by Karen L. Parker.
The Forest Products Laboratory is maintained in cooperation with the
University of Wisconsin. This article was written and prepared by U. S. Government employees on official time, and it is therefore in the public domain and
not subject to copyright.
LITERATURE CITED