Colorado blue spruce (Picea pungens) has been a mainstay of landscapes in the Midwest for decades. This popular tree was quickly and broadly adopted in landscapes for its form and, most especially, for its outstanding color. For most of this time, however, spruce trees have been affected by several chronic disease issues, including rhizosphaera needlecast and cytospora cankers. Liberty Hyde Bailey noted the longstanding problem of cytospora cankers in blue spruce more than 80 years ago in his 1933 volume, The Cultivated Conifers. In the past five to seven years, blue spruce in Michigan and surrounding states have declined at an accelerating rate.
Research by Dr. Dennis Fulbright, Dr. Andy Jarosz and their colleagues at Michigan State University indicates that additional pathogens, particularly cankers caused by phomposis, are likely involved. At this point it is unclear why phomopsis, which is typically a weak pathogen, is contributing to rapid decline of spruce.
Regardless of the underlying cause of spruce decline, homeowners and landscapers may be inclined to throw up their hands in despair. When we consider the impacts of insects and diseases on other long-time favorite landscape conifers in Midwest, such as Austrian pine and Scots pine, it’s natural to wonder, “What can we plant?” While the causes and potential remedies for blue spruce decline are under investigation, homeowners and landscapers looking for substitutes should consider a range of options.
As with many major pest issues on landscape trees, one of our best defenses is increasing species diversity. Over-planting is almost certainly one of the contributing factors to spruce decline. Fortunately there are several lesser known, large- to medium- sized conifers that can fit many of the same design functions as blue spruce. These conifers can be planted as individual specimens or as a group or screen. They include a range of species and genera and offer the potential to add diversity and variety to a landscape.
Concolor fir, Abies concolor
Concolor fir (or white fir) is a medium to large tree that is native to the western United States and grows 1 to 2 feet per year on good sites. Concolor fir trees have blue needles, often as blue as many blue spruces. Unlike many other firs, concolor fir can handle slightly alkaline soils. Avoid excessively wet sites and frost pockets, since concolor firs often break bud early, resulting in frost damage in the spring. Several cultivars have been selected for intense blue color, including ‘Blue Cloak’ and ‘Candicans’. Hardy to Zone 4 (-30 to -20°F).
Korean fir, Abies koreana
Korean fir is another selection that grows well in the Midwest and can tolerate a broader range of sites than most firs. Korean fir is an intermediate grower, about 1 foot per year. Needles are dark green with a silvery underside. Korean fir often produce copious amounts of cones, and some selections, such as ‘Blue Cones’, have been made based on cone characteristics. Another popular cultivar is ‘Horstmann’s Silberlocke’, noted for its silvery recurved needles. Hardy to Zone 5 (-10 to -20°F).
Dawn redwood, Metasequoia glyptostroboides
Dawn redwood is a deciduous conifer that adds a unique appeal to the landscape. This is a fast growing tree (1 to 2 feet or more per year) with a tightly pyramidal growth form. Dawn redwood is native to China and was thought to be extinct until its discovery by scientists in the 1940s. The needles are soft green and shed in the fall to reveal interesting bark patterns. A few cultivars are available; one of the most noteworthy is ‘Gold Rush’, which has bright yellow foliage. Hardy to Zone 4.
Alaska cypress, Cupressus nootkatensis (Chaemacyparis nootkatensis, Callitropsis nootkatensis, Xyanthocyparis nootaktensis)
In the Pacific Northwest where it is native, this tree is commonly referred to as Alaska yellow cedar. In the Midwest, it is usually called Alaska cypress or Alaska falsecypress. Despite what we learned in college about using scientific names to eliminate confusion, the scientific nomenclature of this tree is even more muddled than its common name. Following the discovery of a related conifer in Vietnam in 1999, various taxonomists have classified Alaska cypress in at least four different genera. The current consensus in the scientific literature seems to have settled on Cupressus nootkatensis, though it seems likely that Chamaecyparis will persist in the nursery trade for some time.
Regardless of what you call it, Alaska cypress is a large, graceful plant that makes a wonderful specimen tree. It is a fast grower—1 to 2 feet per year—and is native to the Cascade Mountains from Oregon to Alaska. Alaska cypress is an upright tree with weeping branches. Several cultivars have been selected for extremely narrow, upright form including, ‘Green Arrow’ and ‘Strict Weeping’. Hardy to Zone 4.
Serbian spruce, Picea omorika
Serbian spruce has become an increasingly popular conifer for landscaping in recent years. This is a large tree (growing 1 to 3 feet per year) with an upright, weeping form. One of the most attractive features of Serbian spruce is its blue-green needles, which have silvery undersides. Numerous selections are available in the nursery trade, including the upright, narrow forms ‘Pendula Bruns’ and ‘Berliner’s Weeper’. Hardy to Zone 4.
Swiss stone pine, Pinus cembra
Justin “Chub” Harper, former president of the American Conifer Society, was effusive in his praise of this tree, and it’s impossible to think of Swiss stone pine without hearing Chub’s famous line, “I never met a cembra I didn’t like.” Harper’s affection was based on the consistency and durability of this species; regardless of where they are planted, Swiss stone pines always look good. This is an intermediate- sized (growing 1 foot per year), upright tree. It is native to central Europe, and is a very reliable grower in the upper Midwest. It is in the white pine group (needles in groups of five) with striking, dark-green needles. Cultivars include ‘Chalet’ and ‘Silver Sheen’. Hardy to Zone 3 (-40 to -30°F).
Korean pine, Pinus koraiensis
Korean pine is also in the white pine group. The best way to think of Korean pine is as a tougher version of our native eastern white pine. Like Pinus strobus, this Asian native has soft, light-green needles but is slower growing than eastern white pine (about 1 to 2 feet per year) and is more broadly adapted. It also tends to have a broader outline. Hardy to Zone 4.
Baldcypress, Taxodium distichum
Like dawn redwood, baldcypress is a fast-growing deciduous conifer that grows well even in wet sites. The two species are sometimes confused, but baldcypress tends to have a coarser branch structure and more irregular crown than dawn redwood. Also, baldcypress foliage has an alternate arrangement, whereas dawn redwood is opposite. Although it is native to bottomlands in the southern U.S., baldcypress grows well in Lower Michigan and can tolerate relatively dry conditions. Hardy to Zone 4.
When choosing an alternative for blue spruce, remember to select the right plant for the right place. It’s fortunate that there are such outstanding trees from which to choose.
American Conifer Society, http://www.conifersociety.org
The Gymnosperm Database, http://www.conifers.org
Fulbright, D.W., S. Stadt, and J. O’Donnell. 2012. Michigan awash with Phomopsis cankers on spruce trees and seedlings. Michigan State University Extension News, April 27, 2012.