JARS v61n4 - Evergreen Eden In the Northwoods

Evergreen Eden In the Northwoods
Michael Heim
Hayward, Wisconsin

After a long intense day of teaching and dealing with people, I find it soothing to come home and let my introverted side come out by quietly taking in a woods filled with exotic evergreens. The leaf shapes and textures and their palette of green are a visual smorgasbord. Although southern magnolias aren't reliably hardy in our Wisconsin northwoods (believe me, I've tried), other foliage makes a fairly decent substitute. Specifically, of course, that of rhododendrons. Even though I find the whole gamut of rhody leaves lovely, from the massive bright green ovals of Rhododendron brachycarpum Tigerstedtii Group to the dense dark glossies of R. bureavii , by far the most exotic are the huge straps of R. maximum . Its intraspecific variation is also quite interesting. Plants from a disjunct population in central Vermont carry uniformly smaller, lighter leaves than those originating farther south.

Rhododendron maximum and Dryopteris 
X complexa
Rhododendron maximum and
X complexa .
Photo by Michael Heim

Another favorite, whose foliage reminds me of a tropical rain forest, is mountain laurel. Unlike the rhodies, it can be enjoyed even in the coldest winter weather since its foliage doesn't curl up tightly. One seedling which I collected from a New Hampshire population develops excellent red new growth much like Pieris japonica . Once it gets larger I hope to propagate it from cuttings. Numerous companion plants thrive in this hilly woodland. These include Thujopsis , Cephalotaxus , four species of yew and of cypress, two of beargrass, Leucothoe , and Shortia respectively, several low hollies, numerous exotic evergreen ferns, dwarf irises, box huckleberry, and sundry forms of Pachistima myrsinites and grape hollies collected as cuttings in the northern Rockies.

Leiophyllum buxifolium
Leiophyllum buxifolium .
Photo by Michael Heim

Fondness for our native evergreens causes me to always be on the lookout for outstanding forms. Several attractive clones of trailing arbutus, one with large uniform leaves and another with bright green wavy leaves, were grown from cuttings collected in northern New England. Robust forms such as these can exist there because of effective deer population management. Over the years I've sadly watched the decimation of our native evergreen groundcovers. Thus, the woodland where I'm growing the aforementioned evergreens is by necessity surrounded by a five-foot tall chicken wire fence. At a distance it blends in so well that it's virtually invisible and it is quite effective in keeping deer out. Apparently they have difficulty judging its height. The forest enclosure also contains a form of wintergreen from near Lake Superior fully 8 inches tall and an assortment of partridgeberry forms possessing larger than average foliage. Of these diminutive coffee relatives, the most robust in both leaf size (nickel) and height (five inches) hails from a "lost world" in the Blue Hills of northern Wisconsin where it is surrounded by bare, quartzite boulder-strewn slopes, sheltered from both fire and deer and not reached by the last glacial advance. Springs and cold air flow from the base of the talus year round, even in the hottest, driest weather. Nearby I found another outstanding partidgeberry with beautiful glossy yellow-veined leaves, along with a foot-tall clubmoss having thick foliage. The latter was easily propagated via root cuttings. As an experiment to compare cold-hardiness, other partridgeberry cuttings in the enclosure were collected in southern Louisiana on the last solid ground before salt marsh. All but one perished their second winter when the temperature dropped to –28°F early on without the benefit of thick snow cover.

Skimmia japonica f. repens
Skimmia japonica f. repens .
Photo by Michael Heim

On the other hand, some exotic plants do surprisingly well with the rhodies if grown quite low and given minimal snow cover in the coldest weather. Among these are Skimmia japonica f. repens , several Prunus laurocerasus (especially 'Zabeliana'), Osmanthus decorus , Cryptomeria , certain coast redwoods, Podocarpus lawrencii (from Australia!), Haberlea (a hardy gesneriad), the strap-leaved evergreen Nippon lily ( Rohdea ) and evergreen lily-of-the-valley ( Speirantha ). Camellias are a favorite of mine and I've tried them time and time again with apparent success, only to have them all die some winter for no obvious reason. Their foliage remains fine, so the problem may lie with the roots.

Rhododendron 'Angel'
Rhododendron 'Angel'.
Photo by Michael Heim

Not all of my rhododendrons are growing in, or even prefer, a sheltered woodland site. The P. J. Mezitt hybrids for instance thrive with low manzanitas on a hot and frequently bone-dry ridge behind a cactus and yucca bed. At the opposite end of the spectrum (and yard) is a mossy bed where Rhododendron forrestii ssp. forrestii Repens Group creeps along the side of an old stump. Some of its companions are devil's club, Hartford fern, blue poppies, Selaginella douglasii , sword ferns, Tanakaea , Glaucidium , Stewartia , Soldanella , and tall gentians. An evergreen bed accents the center of our front yard with tall Rhododendron catawbiense (a TN cutting) and Finnish hybrids, along with R. 'Anna H. Hall', R. 'Balta', R. 'April Reign', R. degronianum ssp. yakushimanum 'Angel', mountain laurels, and Leucothoe . Beneath them grow mats of lingonberry, Pieris nana , Pyracantha , and especially Andromeda polifolia 'Macrophylla', its dense glossy reticulated foliage covered with pink bells in spring. Most folks don't believe that rhododendrons can be grown in Zone 3, so it's always a pleasure to observe visitors' reactions when they pull up by this thriving evergreen thicket.

Leucothoe fontanesiana
Leucothoe fontanesiana .
Photo by Michael Heim

One other planting deserves mention. In the sunniest part of the front yard is our sandy heath bed, filled with low ericaceous and other exposure-loving plants such as brooms. Originally it held a collection of heaths and heathers, but most of these suffocated one winter when the snowplow pushed deep compacted snow over them. Now manzanitas ( Arctostaphylos X media and A. X coloradensis ) and bearberry dominate, with penstemons, sheep laurel and sandmyrtle rising above them. At the foot of the sandmyrtle grow two rhodies with flowers all out of proportion to their dwarf stature: Rhododendron calostrotum ssp. keleticum with purple flowers and R. 'Wren' with yellow. Around and amongst them creeps a white flower carpet of pyxie-moss ( Pyxidanthera ) and a sweetly-scented pink-flowered trailing arbutus that I collected not in some distant locale, but just down the road.

Kalmia latifolia 'Sarah'
Kalmia latifolia 'Sarah'.
Photo by Michael Heim

All of the aforementioned plants survived our 2002-2003 "winter from hell" (barely a dusting of snow, much wind, and temperatures holding well below zero for weeks on end). By mid-February the ground in the woods was frozen seven feet deep. I lost many of my favorite plants that winter, including numerous Magnolia grandiflora seedlings, "hardy" cedar-of-Lebanon, dawn redwoods, Cunninghamia , most Southern Hemisphere conifers, snow gum, Trachycarpus palms, Erica tetralix , Ilex crenata and I. glabra 'Chamzin' ('Nordic'), plus a four-foot tall giant sequoia which I had grown from seed. Even so, I'm amazed that so many different plants survived these punishing conditions. For instance, the bright-red flowered Kalmia latifolia 'Sarah' came through unscathed out in the open. That's what makes testing these plants so exciting. It seems almost like a miracle, seeing them in all their green glory, withstanding the bitter-cold North.

Mike Heim has a master's degree in horticulture from the University of Minnesota and teaches science at a tribal high school where he makes full use of the greenhouse to get his students excited about plants. He is passionate about plant exploring and propagating exceptional forms found in the wild.