Hemlocks Are Among the Most Striking and Graceful Conifers in Michigan Landscapes

Text and photos by Dr. Bert Cregg

Hemlocks are among the most striking and graceful conifers in Michigan landscapes. Unfortunately, due to their exacting site requirements, hemlocks can be among the most frustrating conifers for homeowners and landscapers to grow and maintain. Worldwide there are eight to ten species in the hemlock genus (Tsuga), which occur in moist, temperate parts of North America and eastern Asia. Four Tsuga species are native to North America. Western hemlock (T. heterophylla) and mountain (T. mertensiana) occur in the Western US and Canada. Eastern hemlock (T. canadensis) and Carolina hemlock (T. caroliniana) are native to eastern North America. All of the North American hemlock species grow to be large trees in forest stands. Western hemlock is the largest, growing to over 200’ tall. Hemlocks are valuable trees for lumber and for pulp production. Hemlock bark has a very high tannin content and was used by many native peoples for tanning. Native tribes in the Northwest used hemlock to dye fishing nets to make them less visible to fish in murky water. In eastern North America, T. canadensis bark was used for commercial leather tanning until the advent of synthetic tanning materials. Tsuga canadensis 'Everett Golden' November/December 2004 27 Tsuga canadensis 'Frosty' Tsuga canadensis 'Le Bar Whitetip' Tsuga diversifolia

Beyond their use for lumber, pulp, Pacific Northwest and in Europe, both and tannin, hemlocks are among the the straight species as well as several elite of landscape conifers. Their cultivars. Generally it has been assumed color, texture, and graceful elegance that climatic extremes preclude their use add a touch of class to any landscape. in the Midwest but most cultivars in the Named cultivars exist for all four of the trade are from coastal selection (Zone 'Guldemond's Dwarf' North American species, though T. 7). Exploration of the interior range canadensis are the most numerous and (Zone 5) may yield selections with most widely used in the Midwest. The increased tolerance of environmental American Conifer Society lists over 240 stresses. Western hemlock is the state cultivars of T. canadensis, compared tree of Washington.

Tsuga canadensis with 11 for Carolina hemlock, 17 for T. mertensiana and 8 for T. heterophylla. Tsuga diversifolia, There are a handful of named cultivars Northern Japanese hemlock for some of the Asian species of Tsuga Native to the Japanese islands of including southern Japanese hemlock Honshu and Kyushu, T. diversifolia is (Tsuga sieboldii) and Northern Japanese hardy in the southern half of the Lower hemlock (T. diversifolia). Peninsula (Zone 5). Susan Eyre of Rich’s Regardless of the species or cultivar, Foxwillow Pines Nursery Northwest of one consideration common to growing Chicago lists this among her “Top Ten” all hemlocks is the need to pay careful conifers. Northern Japanese hemlock attention to site selection. While has dark green foliage with copious hemlocks can and do grow in open small cones. sites, invariably they perform best in protected areas. Conifer expert Chub Tsuga Canadensis, Harper has a simple rule for choosing sites for hemlocks: avoid winter sun. Eastern hemlock Chub states, “The north side of a In his Manual of Woody Landscape structure, or the north side of a conifer Plants, Michael Dirr states that if windbreak works best.” Like many he could plant only one conifer it conifers, hemlocks grow best on acidic, would be a Tsuga canadensis. Eastern moist, well-drained soils. Hemlock makes up the vast majority of hemlocks in the nursery trade in the upper Midwest. In a quick survey of Tsuga heterophylla, catalogs from three major landscape Western hemlock nurseries specializing in conifers, I The range of western hemlock is found 40 cultivars of T. canadensis. The disjunct with a coastal distribution from only other hemlocks listed were straight southern Oregon to southern Alaska species (T. diversifolia, T. sieboldii, T. and an interior distribution in northern dumosa) and one cultivar of T. sieboldii. Idaho and interior British Columbia. T. The diversity of Eastern hemlock heterophylla is used in landscaping in the cultivars is truly remarkable; selections

28 The Michigan Landscape™ Robert Anderson Tsuga canadensis 'New Gold' Tsuga canadensis 'Callicoon' Hemlock wooly adelgid include large trees, weeping forms, ‘Pendula’ A classic weeping plant for Hemlock Wooly Adelgid variegated forms, dwarf, and miniature the shade garden. (Zone 4) The hemlock wooly adelgid is a plants. In fact some of the smallest serious pest affecting hemlock forests miniature cultivars recognized by the ‘Palomino’ A globe form of dwarf and hemlocks in landscapes in the American Conifer Society are selections hemlock that belongs to the cinnamon- eastern United States. According to of T. canadensis. tip group. It forms a very dwarf the USDA Forest Service the hemlock compact bush with irregular congested ‘Sargentii’ This extremely handsome wooly adelgid has been detected growth. (Zone 4) mounding form can get quite large with in nearly half of the range of eastern age. Chub Harper notes: “I still have a hemlock. Over 55% of 26,000 acres ‘Hussii’ Broad oval to upright dwarf specimen with a trunk diameter of 15" of hemlock forests in New Jersey have (3'–6' at age 10) short dark green that was too big to move with the rest been severely impacted by the adelgid. needles. (Zone 4) of the collection that went to Hidden Fortunately the hemlock wooly adelgid Lake Gardens.” (Zone 3) has not yet established a foothold in ‘Minuta’ One of the smallest of all Michigan. The hemlock wooly adelgid ‘Lewis’ This is a dwarf, upright form conifers this miniature grows less than is an aphid-like insect that infests growing 3–6' at age 10. Chub notes: 1" per year. Like Hussii and Jacqueline hemlock foliage resulting in severe “This is a dandy hemlock, not nearly as Verkade, this slow-growing form is defoliation that can be severe enough to fussy as some.” (Zone 3) suitable as a specimen in rock gardens. cause mortality. The adelgid is an exotic ‘Stewarts gem’ A compact globe pest that was introduced from Asia ‘Gentsch white’ Globe form with form. A very compact plant, growing (sound familiar?). The initial infestations creamy white new growth, intermediate to only 15" by age 18. (Zone 4) in North America occurred in the Pacific size: 6–12" per year, 6–15' at 10 years. Northwest in the 1920s. The adelgid ‘Geneva’ The American Conifer (Zone 3) has not caused widespread damage Society lists this as an intermediate to western hemlock (T. heterophylla) grower (6–15' at age 10) and the ‘Frosty’ Variegated Dwarf form with or mountain hemlock (T. mertensiana) specimen at Hidden Lake Gardens is in a globe habit. 1–6" per year, 3–6' at 10 but has been devastating to eastern this range. This is a reliable hemlock years. (Zone 4) hemlock and Carolina hemlock (T. that is available through several specialty caroliniana), neither of which has shown nurseries but is usually listed as a slower ‘Lebar white tip’ Variegated form resistance. The range of the adelgid grower. Medium to dark green foliage with creamy white-tipped foliage. Broad has increased steadily over the past (Zone 3) upright or oval, up to 15' by age 10. decade. Quarantine on hemlocks from (Zone 5) ‘Jeddeloh’ A widely cultivated low southern nurseries has helped to keep mounding or nest-like plant. Very this pest out of Michigan. Researchers ‘Watnong Star’ Chub notes: “My striking, 3'–6' at age 10. (Zone 3) are examining whether cold winter favorite of all dwarf hemlock, the new temperatures in the northern end of ‘Everett golden’ One of the few growth has a star-like appearance.” the T. canadensis range may limit the golden forms of hemlock. An upright Reportedly hard to find, I found it northern extent of the infestation. small tree. Has best color in full sun but listed in Arrowhead Alpines catalog. will burn. Performs well in light shade. (Zone 4) A dwarf form (3'–6' at age 10). (Zone 4)

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