by Dr. Bert Cregg

n the previous issue of Conifer Corner, I introduced the Cupressaceae or cypress family. IThis family consists of evergreen trees and shrubs that are characterized by having flattened or scale-like leaves. It includes a wide variety of trees that are important in landscape, forestry, and conservation systems. Last time I discussed members of the Cupressaceae that are commonly referred to as “cypresses” or “false cypresses” such as the genus Chamaecyparis. In this issue I’ll present trees and shrubs that are often referred to as “cedars” or “redcedars”. This includes the genera Thuja and Juniperus, which, botanically speaking, are not true cedars (see sidebar).

32 The Michigan Landscape™ Thuja: One of the remnants of my out canoes and pounded the tree’s listed as ‘Emerald Green’. This is forestry training is that I still refer stringy bark smooth for clothing and a dark green, upright to fastigate to Thuja plicata as Western redcedar even diapers for their infants. While form. Chub notes: “This is the only and Thuja occidentalis as Northern today most parents prefer Pampers™ arborvitae to crack my list of 25 white-cedar, although I’ve been around to pounding bark, there are many favorite conifers.” (Zone 4) T. plicata cultivars that are used in horticulturists long enough that I’ve ‘Hetz Wintergreen’: Conical, landscaping. become conditioned to using arborvitae narrow, upright, robust growing, with as a common name. Interestingly, the ‘Elegantissima’: This cultivar is rated compact bright green foliage; tends common name arborvitae (meaning “tree as an intermediate grower by the to grow with a strong central leader of life”) comes from the fact that Native American Confer Society (6"-12" without special training; excellent Americans taught early French explorers per year). Chub notes: “This is an year-round screen (Zone 3) to use foliage from Thuja occidentalis to upright form that is doing very well at ‘Sunkist’: Striking bright yellow to prevent scurvy. By almost any measure, the Heartland Collection in Clinton, golden; fast growing, dense, broad, the number of arborvitae cultivars in the Iowa.” (Zone 5) nursery trade is staggering. The American conical plant; one of the best in this Conifer Society Database lists over 150 ‘Virescens’: Another T. plicata with color class; Chub notes: “It’s a dandy. cultivars of Thuja occidentalis and Michael an upright habit; dark green tree with Train to a single leader.” (Zone 3) an elegant form (Variously listed as Dirr Lists 40 cultivars of Thuja plicata. ‘Holmstrup’: Upright, intermediate Zone 4 or 5) The vast number of cultivated varieties is grower (6"–12" per year); medium a testament to great variability with the ‘Excelsa’: Another of Chub’s favorites green color; Chub notes: “Need two species as well as their relative ease that is doing well at the Heartland to keep this as a single leader when of propagation by rooted cuttings. In the Collection (Zone 5) young. If you let it do it’s own thing, trade arborvitae are often distinguished you’ll have trouble with heavy, wet Thuja occidentalis: Eastern simply by cultivar and frequently little snows.” (Zone 4) attention is paid to whether a cultivar is arborvitae or northern white-cedar T. plicata or T. occidentalis although Dirr is the eastern cousin of T. plicata. ‘Recurva Nana’: Dark green with suggests that T. plicata is superior from an The main range of northern white- a mounding form; Chub notes: ornamental standpoint. cedar extends through the southern “One of the best. Less problem with part of the eastern half of Canada snow loads than many of the globe Thuja plicata: In its native range and the adjacent northern part of forms.”(Zone 3) western redcedar is a massive tree. The the United States. In Michigan this Juniperus: This genus includes National Champion western redcedar species occurs throughout Michigan’s about 50 species, 11 of which are is over 150' tall and nearly 20' in Upper Peninsula, in the northern half native to North America including diameter. This species is highly valued of the Lower Peninsula, and along the Eastern redcedar (Juniperus for its decay resistant lumber and is Lake Michigan shore. As mentioned virginiana) and Rocky Mountain widely used for shakes and shingles. The previously, this species includes a wide juniper (J. scopulorum). Both species tree is referred to as the cornerstone of array of cultivars that range in size are commonly grown in conservation Native American culture in the Pacific from dwarf conifers to large trees and nurseries and they are important trees Northwest. Native Americans used the span the range of forms from creeping for conservation forestry plantings trunks of western redcedar for dug- to columnar. A note of caution, many such as windbreaks and living snow popular globe forms of arborvitae such fences. Eastern redcedar wood is highly as ‘Golden Globe’ and ‘Rheingold’ are valued for its scent and decay resistance. attractive landscape plants when young And, of course, juniper berries are but often have trouble withstanding responsible for the characteristic flavor snow-loads as they get larger. Many of of gin. Although named cultivars of J. the upright forms will hold up better virginiana and J. scopulorum have been through years of Michigan winters. developed, most of the Junipers in the ‘Degroots Spire’: This columnar landscape trade are exotics. form can be planted as a single Juniperus squamata specimen or used in narrow situations for screening. (Zone 4) ‘Prostrata’: Prostrate, ground- covering form with blue foliage that ‘Smaragd’: The trade name is often

September/October 2004 33 eventually mounds in the center; ‘Robusta Green’: Versatile and True Cedars. Although many members Chub notes: “This has proven one of durable landscape plant for accent, of the family Cupressaceae are commonly the best prostrate forms of junipers for windbreak or screen for narrow referred to as cedars, botanically speaking the Midwest because of its resistance spaces; irregular columnar form; none of them can truly call themselves to Phomopsis tip blight.” (Zone 4) (Zone 4) cedars. True cedars (genus Cedrus) are needled conifers that are actually members This Juniperus horizontalis: Juniperus communis of the pinaceae family. Cedrus species are species includes nearly 60 cultivars but characterized by needles borne on short many begin to look shabby with age ‘Effusa’: A spreading juniper with shoots in tufts of 20–30, much like larches. due to Phomopsis blight. shiny foliage that grows 15"–18" tall; (Zone 3) The genus includes four species: deodar ‘Blue Rug’: This is a nice blue-green, cedar, which is a popular ornamental in ground-hugging juniper for spilling ‘Compressa’: Very narrow upright Europe and milder parts of the US such over rocks or as a perimeter plant. form; slow growing (1"–6" year); a as the Pacific Northwest; Atlas cedar (Zone 3) good choice for rock gardens; (Zone (Cedrus atlantica), Cypress cedar (Cedrus 4) brevifolia) and Cedar of Lebanon (Cedrus ‘Mother Lode’: Bright yellow ground libani). Cedars are large stately trees hugging form; excellent groundcover; Juniperus sabina and their foliage gives them a unique relatively low-maintenance once ‘Calgary Carpet’: Compact, characteristic. Unfortunately, cold winter established (Zone 3) spreading evergreen with attractive temperatures limit the use of true cedars ‘Venusta’: Striking prostrate form soft green foliage; excellent low- in Michigan. A subspecies of Cedrus (Zone 5) growing accent shrub; (Zone 3) libani (ssp. stenocoma) is hardy to zone 5 and there is a wonderful, large specimen Often fast ‘Skandia’: spreading, densely Juniperus chinensis: at Hidden Lake Gardens in Tipton, growers; Chub notes: “Be careful with branched ground cover useful for Michigan. chinensis, they often get too big and border or rock garden accent; very can overwhelm a landscape.” durable in the landscape; holds its bright green color well through ‘Saybrook Gold’: Gold color winter (Zone 3) of the new growth is set against a background of green and gold variegation on older needles; slight orange cast to the winter color; (Zone 4)

Thuja occidentalis ‘Degroots Spire’

Justin “Chub” Harper is widely known as one of the leading experts on garden conifers in the United States. The Harper Collection of Dwarf and Rare Conifers at MSU’s Hidden Lake Gardens is nationally recognized. Each “Conifer Corner” includes Chub’s notes on his favorite (and not so favorite) conifers.

34 The Michigan Landscape™