A publication of the Nebraska Statewide Arboretum The Seed Spring 2007 Plains-proven plants to know and grow The Value of Large Trees

Justin Evertson are just some of the ways we relate directly to trees. These physical and Not that long ago most Nebraska mental comforts are so uplifting that communities were full of large American many people develop a very strong elms. Their tall, arching habit, fast spiritual connection to trees. What else growth and adaptability to a wide range explains people who have climbed or of soil conditions made them a popular chained themselves to important trees to choice for planting in towns from prevent their destruction? Falls City to Chadron and all points in between. Because of its wide-spreading The Big Tree Disconnect habit, American elm was especially Because we now know how truly popular for planting along streets. Often valuable large-growing trees are, people the canopies of individual trees met over and communities must be doing all they the middle of the street, creating a ceiling can to properly plant and care for them. of green that would sometimes stretch for Right? Wrong!! In fact, according blocks at a time. Unfortunately Dutch to research by the Nebraska Forest elm disease raced across the state in the Service, the amount of tree canopy cover 1960s and 70s and, in what now seems provided by large trees in most Nebraska like the blink of an eye, the elms were communities has declined significantly gone. And they have been sorely missed. since the days of the American elm. Although the benefits weren’t When the elms died, many were never completely understood at the time, replaced. And where replanting did those who planted the elms knew large occur, smaller-growing trees—selected Large trees frame roads in Nebraska City’s trees were important to a community. primarily for spring flowers or fall Steinhart Park. Today, thanks to research from across color—were often the choice for the country, we can now quantify planting. This trend toward smaller trees community’s tree resource. Having a Inside economically many of the benefits has now been broadly referred to as the wider variety of species greatly reduces the risk of a massive die-off of trees that large trees provide. For example, “dwarfing of the community forest.” The Truth about Roots properly placed and well-cared for Another disturbing problem facing when the next disease or insect comes trees can increase property values by community forests is the lack of species along. Incredibly, the Dutch elm disease 10 percent or more while reducing diversity. If any lesson should have lesson was somehow forgotten and once An Ode to Hackberry energy costs by up to 15 percent. Other been learned in the wake of Dutch elm again a single species of shade tree, this measurable benefits from trees include disease, it is that a broader diversity of time green ash, has come to dominate Pine Wilt Disease and cleaner air, reduced atmospheric CO2, tree species is vital to the health of a The Value of Large Trees continued on page 5 Emerald Ash Borer better-managed stormwater, extended life of streets, more attractive communities and better human health and well-being. Trees with a Split When added together, the benefits of Personality large-stature trees can exceed $65/tree/ A Few Big Trees for the Future year*. Bob Henrickson The Simple Act of Of course people also benefit directly from trees through the mental One of the benefits of working Planting Better Trees and physical comforts they provide. for the Nebraska Statewide Arboretum The coolness of the shade on a hot (NSA) is the opportunity to visit its Return of the Elm summer day; the sounds of rustling network of arboretum sites, parks, historic properties and other public leaves and singing birds; a squirrel flying Ten Elms to Try effortlessly through the branches; the landscapes that spans the entire state. wondrous fragrance of linden blossoms Most of the landscapes that make up the in late spring; the colorful change of Arboretum are not extensive landscapes Fifty Large-growing leaves in autumn; and the magic of but local arboretums and parks where Trees for Nebraska frosted branches on a winter morning… an impressive variety of trees has been assembled. I have visited most of the Arboretum sites over the years and I Tree-planting for Success arboretum.unl.edu Phone: 402-472-2971 Lincoln, NE 68583-0715 University of Nebraska P.O. Box 830715 Nebraska Statewide Arboretum learn something new every time. By definition an arboretum is a place where trees for grown for the purpose of education, and what better place to become familiar with new tree selections or alternatives than a local arboretum? Forest Lawn Cemetery in Omaha is home to many People want to plant trees they are stately trees, including this large tuliptree. familiar with and have seen in the landscape. They also want to be assured that they will grow under regional conditions. A local arboretum is the Tuliptree perfect place to observe and learn about Liriodendron tulipifera plants they might not be familiar with. Native to the eastern half of the U.S., Below is a list of some of the the tuliptree is a stately tree for large wonderful trees I’ve observed or grown. spaces. The leaves are waxy and smooth, Generally they remain confined to retaining a clean appearance through the U.S. Postage PAID arboretums and parks, but in my opinion summer and turning bright yellow in fall.

Nonprofit Org. they have a lot of potential and have The flowers are the size and shape of Nebraska Lincoln, NE

Permit 46 proven they should be planted more. garden tulips, blooming in May after the Statewide These trees have stood the test of time. first leaves have expanded. The beautiful It’s time to get them out of the arboretum two-toned orange-yellow petals are often rboretum and into our home landscapes. A Few Big Trees continued on page 2 arboretum.unl.edu A Few Big Trees continued from cover Turkish Filbert hidden by the foliage and are best viewed Corylus colurna from a two-story window. There are This uncommon tree is handsome, beautiful trees growing on the campuses sturdy and trouble-free. The deep green, at the University of Nebraska in Lincoln toothed foliage remains clean throughout (UNL) and at Midland Lutheran College the summer and seems to be free of in Fremont. The Nebraska champion is insect and disease problems. The gray- located in Oakland, a big, impressive tree brown bark is heavily textured and the with a 4’ diameter trunk. Another large branches develop a very attractive formal specimen is located in a church courtyard outline. In early spring the clusters of in Humphrey, Nebraska. This tree has long male catkins dangle from the bare performed well in the eastern half of the branches like tarantula spiders. Though state and deserves to be planted more. native to Europe and Asia, it seems to thrive in Nebraska and a number Amur corktree of outstanding specimens can be seen Phellodendron amurense at UNL and at the Nebraska Game and Parks Commission headquarters This handsome medium-sized in Lincoln. Out west, a young tree is tree has deep green, shiny leaves that thriving in Lexington at the Dawson remain clean all summer. The bark County fairgrounds, but the best on old trunks is ridged and furrowed, specimen in the state is a 50’ beauty at forming a beautiful cork-like pattern. the Glen Viehmeyer Arboretum in North One of the best features of this tree is the Platte. This tree is underused and can be broad-spreading habit, open crown and difficult to locate in commerce, but it’s horizontal branch arrangements. This worth the hunt! tree is native to the Amur River region in China, the same area as Amur maple and Amur chokecherry. Beautiful specimens Bitternut Hickory of corktree are growing at UNL, Peru Carya cordiformis State College, Steyer Park in Blair and This relatively fast-growing, Memorial Park in Tekamah. An Amur beautiful tree is native to southeast corktree has been performing well in the Nebraska along the Missouri bluffs and Kimball arboretum in western Nebraska along creeks and rivers as far west as for over 12 years. The male selections Wahoo and Beatrice. In rich, woodland ‘Macho’ and ‘His Majesty’ are fruitless sites the bitternuts typically develop and noted for their thick, leathery leaves several primary vertical limbs, forming and spreading growth habit. an arching shape. Their tight, relatively smooth bark and bright yellow fall color Overcup Oak are reason enough to plant this tree. In Quercus lyrata spring, the long male catkins “hang like tinsel from the branches and are visible Overcup oak is the southern below the leaves” (Guy Sternberg, Native counterpart to swamp white oak, native Trees for North American Landscapes). from the southeastern U.S. west to Hickories develop long taproots and Missouri and Oklahoma. This is one of can be difficult to transplant, however the most flood-tolerant oaks and it grows with today’s air-pruning pots and root- naturally on poorly-drained, heavy clay restricting fabrics, the root systems soils. The acorn is almost fully enclosed produce a branching root system. Our by the cup and falls from the tree intact. native seed source should yield a more The cups provide flotation and help adaptable tree for areas throughout to disperse the seeds under flooded eastern Nebraska. conditions. The dark green, leathery The state champion at Wyuka leaves turn dull gold in fall. We have cemetery in Nebraska City is an collected seeds from mature specimens impressive specimen and an 80’ tree has of overcup oak on the grounds of St. thrived for decades less than a block Joseph’s Catholic Church in Auburn, away from one of Lincoln’s busiest Nebraska. Seedling progeny of these streets. A grove of fine, young bitternuts trees are being evaluated by participants can be seen at UNL’s Cather Garden. in our Research Consortium program and nurseries are beginning to carry good- Some of these trees may not be sized trees. A healthy 50’ tree is thriving readily available from local nurseries in a Lincoln neighborhood and in the but that’s largely a matter of supply arboretum oak collection at the Lincoln and demand. When people become Regional Center Arboretum. Michael familiar with these trees, I’m confident Dirr feels this tree could become an they’ll start asking for them, and when important landscape tree, saying he “does customers start asking for them, nurseries not remember an unworthy specimen. will start carrying them. With its adaptability to wet soils it may This is a small example of the be adapted to similar urban conditions.” incredible variety of trees thriving Burgambel Oak in Nebraska. If you haven’t had the opportunity to see these trees, you can Quercus macrocarpa x gambelii count on Nebraska Statewide Arboretum The bur oak, Quercus macrocarpa, affiliates to introduce them to you. is one of our most variable oak species For more information about where to and is prone to hybridize with other see them, call 402/472-2971 or visit white oaks. Many intermediate forms arboretum.unl.edu/affiliate. These trees From top: Gary Zimmer, Curator show genetic influences from swamp may be rare in our home landscapes right of Gilman Park Arboretum in white oak, white oak and others, now, but they won’t be once the word Pierce and Kristina Jensen, NSA including gambel oak. Natural hybrid gets out! Nursery Technician, stand next to populations of bur oak and gambel oak a widespreading Amur corktree (Quercus gambelii) can be found in (Phellodendron amurense) Colorado and Wyoming. The burgambel at the Morton Arboretum near Chicago. oak hybrid is one of the best for acorn For more NSA volunteer Bob Vogel with the production and develops a compact, Nebraska state champion biitternut hickory in Auburn. bushy crown to 40’ high. If you are information on Close-up of tuliptree blossom . limited in space but still want the Early spring catkins of Turkish filbert. durability and adaptability of a bur oak, Overcup oak acorn. then plant burgambel oak. This tree has a recommended trees: lot of potential for harsh, dry landscapes throughout Nebraska, but especially in the western half of the state. It makes its arboretum.unl.edu/ best growth in dry, sandy well-drained sites. Several young trees are thriving on plantinfo the UNL campus.

 The Truth about Roots

Eric Berg, Nebraska Forest Service chemical applications. Soil sterilants and Bob Henrickson, Nebraska Statewide Arboretum materials containing Dicamba for broadleaf control should not be used around trees as It’s hard to overemphasize the these chemicals are persistent and active in importance of a tree’s root system the soil and will severely damage tree root in maintaining a healthy tree and, systems over time. ultimately, a healthy community forest. At the simplest level, the main functions Healthy root systems result in healthy of tree roots are to support the tree and to trees, whether they’re in your backyard, take up the water and minerals essential in your community or in natural forested to overall plant vigor and health. areas. By better understanding some of Probably because they are unseen, the basic biological realities of tree roots, there are many misconceptions and you can better maintain and protect them. myths about this invisible, underappreci- So the next time you do construction ated and essential part of the tree. work, apply herbicide or drive across that seemingly wide expanse of fescue, stop Myth: Tree roots are tough and consider the trees around you and the fragile but critical roots beneath your feet. and woody. Reality: The majority of root biomass is made up of very fine feeder Top: The major portion of a tree’s root system is roots, typically averaging only 1/16” in made up of small feeder roots. Because they are diameter, which are responsible for water fine-textured and close to the surface, they are and mineral uptake. Structural roots easily damaged by compaction, construction dam- age and chemical applications. located near the trunk help support the Bottom: Circling and girdled roots are a common tree and are typically large and strong, problem in container-grown trees. but feeder roots represent the major (Photos courtesy of Eric Berg) portion of the root system’s surface area. The root system of a tree can be thought of as a permanent, structural woody frame with “disposable” fine “In the intimate and roots that may last for only one season due to poor soil growing conditions, humanized landscape, drought or freezing temperatures. In the urban environment, these roots are also trees become the very susceptible to compaction, over- watering, construction damage, water greatest single pollution and soil contamination. Trees can lose as much as 95 percent of element linking their root system in being transplanted and therefore spend a majority of energy us visually and reserves to re-establish them. emotionally with our Myth: Tree roots grow deep surroundings. Other into the soil. manifestations Reality: The majority of tree roots are found in the top 18” of soil, and of nature—great typically over half of a tree’s roots are in the top 6” of soil. Tree roots rocks, deserts, require oxygen for survival. They will occupy and grow in areas favorable moors, torrents, for survival, with good aeration and available moisture and nutrients. These hurricanes—stir types of conditions are easily created with proper mulching. While there are An Ode to Hackberry us, fill us with awe, many instances where a given species Justin Evertson woodlots and other out-of-the-way places make us afraid or might send roots deep into the soil, the within a community. This opportunistic Growing trees in Nebraska can be vast majority are typically just below the nature, however, has one good advantage a risky proposition. If wind, hail, ice humble, but a tree we soil surface—deep enough for reliable –free trees are available for those willing storms, tornadoes, droughts, hot sum- moisture, yet shallow enough for good to transplant them. Indeed, hackberry mers and cold winters don’t kill a tree, understand and can oxygen levels. Poor soil aeration, typical is hard to find in nurseries, so digging a insects, diseases and people often seem of compacted soils, is one of the most seedling is sometimes the best option. ready to finish the job. Thank goodness allow to become part limiting factors for root growth in the The important message here is not for hackberry (Celtis occidentalis). This urban environment. When compaction is to promote the widespread planting of tough-as-nails cousin to the elm has of us. It’s no wonder coupled with over-watering, there is very many more hackberries. Rather, the proven its worth in yards, parks, farm- little pore space left for oxygen and, as a point is to encourage us all to appreciate steads and shelterbelts across the state for that when we first result, roots slowly suffocate and die. the many hackberries we already have, generations. work hard to maintain them properly, and Hackberry possesses many positive think of a garden we Myth: Tree roots exist only when possible, assist in their renewal by attributes that make a good tree for the planting a few here and there so that they under the tree canopy. Great Plains. Its broad, arching growth think of a tree.” will be in our communities for years to habit makes it an ideal species for street Reality: Tree roots typically have come. As I sit and watch the cedar wax- side plantings; its tough character makes Thomas D. Church very extensive root systems growing wings enjoy a late winter meal of hack- it very useful in parks and other public well beyond the canopy of the crown. In berry seeds, on the tree that will almost spaces; its distinctive warty bark and forested or natural environments, roots may fully shade my neighbor’s backyard in clean branching gives it a unique natural be found growing two to four times beyond the coming months, I can’t help but feel character; it is native to the region and the diameter of the tree canopy, and with very thankful for a species that gives so thus uniquely acclimated to the Great drought-tolerant species such as oak, the much while asking for so little in return. spread can be up to six times the canopy Plains environment; it suffers from few width. Roots do not mirror what you see disease or insect problems; it tolerates aboveground. To visualize this, imagine a both wet and dry soils; and its fruits are tree represented as a wine glass connected prized by cedar waxwings and other to a wide flat plate. The glass and stem colorful birds. represent the canopy and trunk and the Hackberry is not perfect. It has been plate represents the root system extending over-planted in some communities and it well beyond the canopy of the tree. This tends to break up in wind and ice storms is very important to consider when dealing when not properly pruned and cared for. with potential construction damage or It can also be very opportunistic (nice word for “weedy”). Birds are able to spread its seeds far and wide and seed- lings are often found growing in alleys,  Pine Wilt Disease and Emerald Ash Borer Justin Evertson has begun to kill Austrian pines. The Emerald Ash Borer disease is advancing north and west Pine wilt disease and the potential across state and shows no signs of Over the last few years, the emerald threat of emerald ash borer have many slowing down. Scotch pine and Austrian ash borer (EAB) has killed millions of Nebraskans concerned about the future pine have been the two most common native ash trees in Michigan, Ohio and of some of the state’s most popular trees. pines planted in the state, especially in Indiana and it has the potential to kill Here are some fast facts about these shelterbelts, over the last 50 years. The most of the ash trees in the eastern U.S. threats. For more information, go to: potential loss from this pest is significant Many experts believe it is likely that the http://www.nfs.unl.edu/program- and could eventually total millions of insect will reach Nebraska (probably on foresthealth.asp trees. As such, Scotch pine is no longer firewood) within the next several years. recommended for planting throughout The potential impact is enormous Pine Wilt most of the state. since green ash is one of the most com- mon trees found throughout Nebraska Pine wilt has already killed Susceptible trees: Scotch pine is highly in communities, on farms and in native thousands of otherwise healthy Scotch susceptible and Austrian pine woodlands. Because of the threat of pine in southeast Nebraska and also somewhat susceptible. EAB, native ash species including green Symptoms: Faded, gray-green needles ash (Fraxinus pennsylvanica), white ash eventually turn brown. Trees (F. pennsylvanica), blue ash (F. quad- die rapidly, sometimes branch- rangulata) and black ash (F. nigra) are by-branch, usually between late no longer recommended for planting in summer and early spring. the eastern half of Nebraska, and should Cause: Pinewood nematode attacks be used only with caution and in limited tissues in the wood, decreasing numbers in the western part of the state. water flow and eventually killing This recommendation includes all of the tree. The nematodes are carried the common native ash cultivars such to other trees by pine sawyer as ‘Patmore’ and ‘Marshall’s Seedless’ beetles, which tunnel in the wood green ash as well as ‘Autumn Purple’ of dying pines (including those white ash. dying from pine wilt). Emerging beetles can carry thousands of Susceptible trees: All North American nematodes on their bodies. As ash (Fraxinus) species and cultivars they feed on new shoots of healthy are susceptible (not mountain-ash pines, they create wounds through or Sorbus, which is not a true ash). which nematodes infect the tree. Symptoms: Exit holes in ash bark about Control: Diseased trees cannot be saved 1/8” in diameter and “D-shaped”; and should be destroyed (burned, zigzag tunnels under the bark; buried or chipped before beetles tunnels packed with sawdust; emerge from the wood) to prevent dieback from top of tree. spread to healthy trees. Highly Cause: Emerald ash borer—slender, Thousands of Scotch pines have died of Pine Wilt Disease (top photo taken in Auburn). Though not valuable trees can be protected emerald-green beetle about ½” long. yet sighted in Nebraska, Emerald Ash Borer has killed millions of trees in more eastern states and with a trunk injection of abamectin, Control: None at present. Trees usually is moving westward toward Nebraska, often by means of transported firewood. available from certified arborists. die within three years of infestation.

Trees with a Split Personality

Bob Henrickson characteristic retained in propagation. used as an understock for many ash Even a quick look at trees growing Many tree cultivars are propagated species and for this reason has been in an urban environment makes it easy by a grafting technique called budding, dubbed “the universal donor.” Though to see the stresses they have to endure. in which a single bud taken from the grafting has enabled us to select cultivars We plant them in pits, parking islands, desired cultivar is nestled within a fold with superior ornamental qualities, these compacted construction sites and made in the lower stem of a seedling trees lack the full genetic representation basement sub-soils and expect them to tree. The initial sideward growth from of a species, including its ability to perform. We forget that Nebraska is a this single bud is what causes the slight overcome a wide variety of stress factors. plains state where prairie once ruled and crook at the base of the stem. The top One of the questions we need to ask where trees were often found only along of the tree, referred to as the scion, is “Will these trees be prone to failure streams and rivers. The plains climate originates from the single bud taken from before they reach maturity?” has always been tough on trees, with a specific tree or cultivar. The bottom, There are well-documented cases damage from wind, ice, heat, drought, called the rootstock or understock, is of graft incompatibility, even when insects and diseases, to name just a few. beneath the scion and consists of the the scion and the rootstock are of the We are familiar with these problems, lower few inches of the stem (where the same species. In the 1970s, many red but we forget that these stresses are bud is grafted) and the entire root system. maples grown from budded trees began even more magnified in the urban In the past, many shade tree cultivars to decline for no apparent reason. environment. were selected for desirable growth Researchers determined that the problem Arborists and other tree habit or fall color, with little regard for was delayed graft incompatibility, i.e. professionals often consider only the drought- or heat-tolerance or adaptability the failure of the graft does not occur top of the tree—leaves, branches and to various soil types. Fortunately, today’s until five to 10 years after budding, trunk—in diagnosing problems. The cultivars are selected not only for shape, when the tree is already established in rootstock or root system, often the size and fall color, but also for how well the landscape. Maples were showing most important part of the tree, is more they tolerate urban growing conditions. premature fall color, dieback and difficult to examine. After planting Two common cultivars in the urban shedding bark; many were dying. and caring for trees over the years, I’m landscape include Autumn Purple white Because of this, nursery growers began constantly reminded that, for the health ash (Fraxinus Americana ‘Autumn developing maple cultivars on their own and performance of a tree, “it’s all in the Purple’), selected from a single specimen roots via cuttings or tissue culture rather roots.” If roots are stressed from poorly in Ohio known for its outstanding deep than grafting. drained, oxygen-deprived soils or from purple fall color and ‘October Glory’ red Ornamental trees endure a lot of compacted or contaminated soil, the maple (Acer rubrum ‘October Glory’) unique, stressful situations in the urban tree will be more vulnerable to insects, selected from a tree with crimson red fall landscape. Their “split personality” may diseases and other problems. color. When the scion wood is collected not be the primary stress they have to While poor soil or planting depth is from these trees we know where the trees overcome, but it is a problem not shared an obvious cause of problems, there is come from, but the origin of the lower by their forest cousins. To truly diversify Top: Most white ash cultivars, including another stress that is rarely considered. portion of the tree or rootstock is usually the urban community forest, we need ‘Autumn Purple’, are budded onto According to John Ball of South Dakota a mystery. Very rarely are we aware of to consider planting more trees that are green ash rootstock. State University, “many of our urban the origin of the rootstock (and yes, that produced from seed. By simply planting Bottom: Red maple cultivars are often prone trees suffer from a split personality… does matter when you consider that red one seed-grown red oak or Kentucky to bark sloughing, due in part to delayed they’re really two trees, the trunk and maples grow naturally from northern coffeetree for every ‘Autumn Blaze’ graft incompatibility. canopy is one species, the roots another.” Minnesota to Florida). maple or ‘Skyline’ honeylocust, we Named cultivars or clones are a group Most white ash cultivars, including can make a good start toward diversity of cultivated plants distinguished from ‘Autumn Purple’, are budded onto green and sustainability in our community  other plants of the same species by a ash rootstock. Green ash is commonly landscapes. The Value of Large Trees continued from cover Poor care. an ironic though predictable twist of Whether through ignorance or fate, an insect called the emerald ash outright neglect, many community trees borer (see article on page 4) is advancing do not get the care they deserve. Over- toward Nebraska. Emerald ash borer has watering, under-watering, mower blight, the very real, and likely, potential to wipe poor pruning, dogs chained to the trunks, out most ash trees, including the green etc. are all common across a community. ash which is the most common shade tree Although it may be naive to think that found in many Nebraska communities. every tree can have perfect care, it So why have we not done a better should be an easy matter to raise overall job of planting and caring for large- care of community trees through better growing trees? Although the reasons can promotion and education. vary from place to place, some common considerations include: Fear of big trees. Many people fear that big trees Our disconnect from nature. will cause big problems—such as large, In our modern world, many falling limbs, higher maintenance costs people live in air conditioned homes and higher removal costs when they and travel to air conditioned offices in need to be taken out. It is true that air conditioned vehicles. Our leisure bigger trees can lose bigger limbs and time is often spent indoors watching they do have higher maintenance costs. TV or going to movies, restaurants However, well-cared for trees rarely have and shopping places. We just don’t significant limb failures and the benefits connect to the outdoors like we used to. of large trees can exceed maintenance Perhaps we have collectively forgotten costs by an 8 to 1 margin*. (or never experienced) the value of shade trees.

Impacts from lawn care. Lush, green lawns have come to dominate planted landscapes across The Simple Act of Nebraska and throughout much of the country. Unfortunately, many of Planting Better Trees the inputs and activities needed to Justin Evertson maintain such lawns can have negative consequences for trees. Over-watering, The writing on the wall is clear: herbicide damage, compacted root zones large-growing trees are very important and trunk injuries from mowers and to individuals as well as communities trimmers are all very common to trees in as they return benefits valued at up to turf-dominated landscapes. $65/tree/year (which is more than four times higher than the value for small Construction and community trees*). And yet, for most communities, development. the number of large-growing trees In any community, trees are often being planted is not keeping pace with in the way of construction activities, removals. In fact the tree cover for most utility work and normal maintenance towns has declined significantly from of the built environment. Tree trunks just a few decades ago. and branches in construction zones are Now is the time to begin the rarely or inadequately protected and significant effort of reforesting Nebraska are frequently damaged from careless communities and to prepare for the equipment operators. An even bigger potential loss of pine and ash trees (see problem is the damage done to tree roots article on page 4) by planting trees at a by trenching and soil compaction from much faster pace and including a much heavy equipment. wider variety of larger-growing species. A cooperative effort must be undertaken to retake the streets, parks and backyards Poor choice of species. from the timid tree-planting activities Many of the shade trees planted of the recent past and once again restore today are selected primarily for such our communities to the tree-filled glories things as uniform shape and habit, a they once were. Such an effort won’t be certain fall leaf color and a desire for easy and it won’t be without cost, but it trees to not be “messy” (often meaning will most definitely be a wonderful gift fruitless). As such, grafted male clones to ourselves and future generations. from just a few species, including green * Estimate from the Center for ash, white ash and red maple, have come Urban Forest Research, USDA Forest to dominate the market. Many of the From top: Large-growing trees are important Service. Additional benefits of large- even in very urban settings, such as this plaza in better-adapted and longer-lived species growing trees can be found at: http:// are not nearly as popular. downtown Kansas City. www.fs.fed.us/psw/programs/cufr/ Trees shade a bench in Atchison, KS. Kentucky coffeetree is one of the most beautiful Poor planting practices. and adaptable large-growing trees for Nebraska. Somehow we have forgotten, or more Here they grace pathways at Harmon Park in likely never learned, how to properly Kearney. plant trees (see article on back cover). For various reasons, many trees planted today are planted too deep and often with significant root problems. Other common mistakes include the failure to remove “A single great tree can make a kind of garden, an entirely new place on the balling twine and burlap, poor staking and poor mulching. land, and in my mind I was already visiting the place my maple made, resting

Poor nursery stock. in its shade. I knew it wouldn’t happen overnight, probably not even in my A mass-market society seeking the lowest cost alternative has led to the lifetime, but wasn’t that precisely the point? To embark on a project that purchase and planting of many low- quality trees. Questionable hardiness would outlast me, to plant a tree whose crown would never shade me but my and pot-bound roots are very significant problems—especially from big-box children or, more likely, the children of strangers? Tree planting is always a stores and other retailers that set up temporary nurseries in their parking lots utopian enterprise, it seems to me, a wager on a future the planter doesn’t each spring. It is important to purchase trees from reputable, local nurseries that necessarily expect to witness.” have the experience and knowledge to stock only the highest quality trees, and Michael Pollan, Second Nature that will stand by their products.  Return of the Elm

Justin Evertson conditions, making it quite common in The most prominent new elms western Nebraska. To this day it remains are resistant to Dutch elm disease. In Until the 1970s, elm trees were the primary shade and windbreak tree addition, many are also resistant to elm perhaps the most common trees planted for our family farm in Kimball County. leaf beetle, thus retaining a much greener in communities across Nebraska. Unfortunately, Siberian elm has also appearance throughout the growing season. American elm (Ulmus americana) was proven to be a weak-wooded and especially popular as its tall, arching Several of the elms are able to “messy” tree with a weedy, invasive habit made it an ideal shade tree for tolerate a wide range of growing habit, making it a tree that is scorned by planting along streets, in parks and in conditions including the poor soils and many people. backyards. In many communities the the extreme climate of the Great Plains. With those stark visions clouding American elm comprised more than half our minds it is understandable why the total species planted in public spaces. The tall, arching habit of some elms fell out of favor and are rarely Unfortunately, Dutch elm disease spread elms makes them especially useful for planted in communities today. rapidly across the state in the 1960s planting along streets and in parks where Fortunately, some forward looking and 70s, killing most American elms many treeless gaps still exist. people have worked hard for many along the way and laying bare the leafy years to develop new elm varieties that The new elms help greatly expand canopies that once graced so many of our should be planted more. New species the diversity of large-stature trees streets. have been discovered, unique forms available for planting in Nebraska. During and after the dustbowl have been hybridized and disease- years of the 1930s, Siberian elm (Ulmus These elms add a variety of resistant varieties of the old American pumila) also became a popular tree interest and beauty to the landscape elm have been developed. across much of Nebraska. The tree through unique leaf, bark and branching There are many benefits to these was able to grow with almost no care characteristics. new elms: and could survive extreme drought So plant an elm!

Ten Elms To Try ‘Valley Forge’ American Elm Japanese Elm with strong branches bearing glossy, Ulmus americana ‘Valley Forge’ Ulmus davidiana var. japonica deep-green foliage. The tree appears to be very adaptable to a wide range of Japanese elm has proven hardy as Several large American elms growing conditions and will grow 50- far north as North Dakota and Manitoba, survived the ravages of Dutch elm 60’tall by 30-40’ wide. Canada. The species has been disbursed disease and have been used to develop by NSA for testing in Nebraska and disease resistant, cloned cultivars early reports are promising, especially including ‘Valley Forge’, ‘New Vanguard™ Elm for eastern Nebraska. The tree is also a Harmony’, and ‘Independence’. ‘Valley Ulmus japonica × pumila ‘Morton parent to many of the more promising Forge’ is recognized as being the most Plainsman’ hybrid elms. Japanese elm has glossy disease resistant. The tree is adaptable Vanguard elm is another Siberian green leaves, relatively tight branching to a wide variety of soil conditions and elm/Japanese elm hybrid which was and a rounded habit with the potential of tolerates deicing salts, air pollution, developed at the Morton Arboretum. growing up to 40-50’ tall by 30-40’ wide. drought, and a range of soil pH. American The tree is considered to be very tolerant elm has an upright, arching habit making it of high heat and drought, thus making an ideal street tree. It can grow 50’-70’ tall ‘Cathedral’ Elm it a promising selection for the western and equally as wide. Ulmus davidiana var. japonica × Great Plains. The tree has dark green pumila foliage, a rounded vase shape and will grow 40-50’ tall by 40-50’ wide. Cathedral elm was developed at the University of Wisconsin by crossing Siberian elm with Japanese elm. It is a Rock Elm fast grower, is tolerant of clay soils, and Ulmus thomasii has a yellow to orange fall color. The Rock elm is native to the eastern tree has a broad, vase shape and grows U.S., including eastern Nebraska. Its 40-50’ tall by 40-50’ wide. relatively narrow and upright habit is reminiscent of pin oak. A very ‘Frontier’ Elm distinctive feature of this tree is the Ulmus parvifolia xcarpinifolia corky ridges found on stems and young branches that eventually develop into a This very attractive hybrid shares deeply fissured bark. Several Rock elms many characteristics of lacebark elm have grown tall and old in Cheyenne, (one of its parents) including small, WY, giving testament to its hardiness glossy leaves that turn a dusty purple in and adaptability. Rock elm can grow 50- the fall, and mottled bark on maturing 60’high by 30-40’ wide. trunks. Although some reports indicate winter dieback in the Great Plains, it has performed well in southeast Nebraska Lacebark Elm for several years. Can grow 30-40’ tall Ulmus parvifolia by 25-30’ wide. The common name of this elm refers to the very attractive mottled, lacy bark Accolade™ Elm ‘Pioneer’ Elm that develops on older stems. Lacebark Ulmus japonica × wilsoniana Ulmus glabra × carpinifolia elm is sometimes called Chinese elm in reference to its native range of China, ‘Morton’ Pioneer elm has been planted in Japan and Korea. The leaves are smaller Accolade elm has quickly become several locations in Nebraska and has than most elms and are deep green and one of the most promising and popular performed well in Creighton, Pierce, very glossy. Flowering occurs in late elm cultivars for use across much of the Waverly and Alliance, among other summer with seed development in early U.S. The tree has an upright, arching communities. It is a fast grower with fall. The yellowish seeds are quite habit that is reminiscent of American dark green leaves and an upright, attractive against the shiny green leaves. elm. This hybrid elm originates from a pyramidal habit when young. Pioneer Many trees also develop a nice reddish tree that has been growing at the Morton elm will eventually be a rounded tree fall color. This tree is best adapted to the Arboretum near Chicago since 1924. growing 40-50’ tall by 40-50’ wide. The tree can grow 50-70’ tall and 40-60’ southern half of Nebraska. ‘Emerald wide. Prairie’ is an exciting new cultivar Triumph™ Elm developed in Kansas that may have From top: Accolade™ elm; leaf of American elm. Ulmus x ‘Morton Glossy’ better cold hardiness. Lacebark elm is a Japanese elm is a graceful tree that has good Triumph elm was developed at medium-sized tree growing to 25-40’ tall potential for the Great Plains. the Morton Arboretum by crossing by 20-35’ wide. Rock elms growing along a street in Cheyenne, Vanguard™ elm with Accolade™ WY attest to the tree’s toughness. Lacebark elm with emerging seeds. elm. It has a vigorous, upright habit  Fifty Large-Growing Trees for Nebraska

Justin Evertson Pear, Callery, Pyrus calleryana, 35’x 25’

Even in a prairie state like Nebraska, Pecan, Carya illinoinensis, E 60’x 50’ there are many trees that will grow well if given a chance. The following 50 Planetree, London, Platanus x species of large-stature trees are suitable for planting in much of Nebraska. All acerifolia, E 75’x 50’ will grow at least 30’ tall. An E indicates trees primarily suited to the eastern half Poplar, Silver, Populus alba, 75’x 60’ of the state. The size listed is the average range of height and spread at maturity. Sycamore, Platanus occidentalis, 80’x 50’

Buckeye, Ohio, Aesculus glabra, 30’ x 30’ Tulip Tree, Liriodendron tulipifera, E 50’x 40’ Catalpa, Northern, Catalpa speciosa, 50’x 35’ Walnut, Black, Juglans nigra, 60’x 45’

Cherry, Black, Prunus serotina, 35’x 20’ Yellowwood, Cladrastis kentukea, E 35’x 25’ Coffeetree, Kentucky, Gymnocladus dioicus, 50’x 40’

Corktree, Amur, Phellodendron Evergreen Trees amurense, 35’x 40’ Douglasfir, Pseudotsuga menziesii, Cottonwood, Eastern, Populus deltoids, 50’x 30’ 80’x 70’ Fir, Concolor, Abies concolor, 50’x 25’ Elm, miscellaneous, Ulmus spp. (see Juniper, Rocky Mountain, Juniperus article on page 6) scopulorum, 35’x 20’ Filbert, Turkish, Corylus colurna, E Pine, Austrian, Pinus nigra, 60’x 35’ 40’x 25’ Pine, Bosnian, Pinus heldreichii var. Ginkgo, Ginkgo biloba, E 50’x 40’ leucodermis, 45’x 30’ Goldenrain Tree, Koelreuteria Pine, Eastern White, Pinus strobus, E paniculata, E 35’x 25’ 70’x 40’ Hackberry, Celtis occidentalis, 60’x 50’ Pine, Jack, Pinus banksiana, 40’x 25’ Hickory, Shagbark, Carya ovata, E Pine, Limber, Pinus flexilis, 50’x 30’ 50’x 40’ Pine, Ponderosa, Pinus ponderosa, Honeylocust, Thornless, Gleditsia 65’x 30’ triacanthos var. inermis, 60’x 50’ Redcedar, Eastern, Juniperus Horsechestnut, Aesculus virginiana, 40’x 30’ hippocastanum, E 40’x 30’ Spruce, Black Hills, Picea glauca var. Linden, American, Tilia americana, densata, 50’x 30’ 60’x 40’ Spruce, Colorado, Picea pungens, 65’x 35’ Linden, Littleleaf, Tilia cordata, 45’x 30’ Spruce, Norway, Picea abies, 70’x 40’ Linden, Silver, Tilia tomentosa, E 50’x 40’

Locust, Black, Robinia pseudoacacia, 35’x 25’

Maple, Miyabe, Acer miyabei, 30’x 25’

Maple, Sugar, Acer saccharum, 50’x 50’

Oak, Bur, Quercus macrocarpa, 60’x 70’

Oak, Chinkapin, Quercus muehlenbergii, 45’x 40’

Oak, English, Quercus robur, 60’x 50’ There’s lots to love if you’re looking for large shade trees for Nebraska. From top: Bur oaks on the campus of Peru State College (“Campus of a Oak, Red, Quercus rubra, 60’x 50’ Thousand Oaks”). Fall foliage of white oak. Creamy, mottled bark of London planetree. Oak, Sawtooth, Quercus acutissima, E Concolor fir (Abies concolor) is one of the most graceful evergreens for 60’x 40’ Nebraska. Many large specimens, including the state champion, can be found at the CABG Patch Arboretum–an NSA affiliate site just north of Omaha. Oak, Shumard, Quercus shumardii, E 50’x 40’

Oak, Swamp White, Quercus bicolor, 60’x 50’

Oak, White, Quercus alba, E 60’x 50’

Pagodatree, Japanese, Sophora japonica, E 40’x 30’  Tree-planting for Success Justin Evertson n All graft unions should be visible above the soil line. Proper planting is critical to the n Remove all pots and containers establishment of healthy, thriving trees. before planting. The following planting guidelines n For balled and burlap (B&B) stock, have been developed to help new try to remove the wire basket and burlap trees get off to a successful start. before placing the tree in the hole. If The recommendations are based on maintaining the integrity of the soil ball nationally recognized standards as well is important, then remove the bottom as experience compiled by the Nebraska part of the burlap and wire basket Statewide Arboretum and the Nebraska before setting the plant in the hole and Forest Service. The recommendations then remove the remaining burlap and assume that an appropriate tree has been wire basket after stabilizing the tree in selected for the planting site and that the the hole. Remember to check for and site is suitable for planting. remove any excess soil at the top of the root ball before planting. n Loosen and spread circling roots before backfilling (especially important for potted trees). It may be necessary to cut larger roots that cannot be straightened to prevent girdling, but this should be done with caution. Reject plants with severely circled or girdled root systems. n For potted trees, try to remove as much of the original growing medium as possible before planting to help achieve good soil-root contact. Dunking in water or spraying with a hose will help in this effort. BACKFILLING Backfill with the original soil dug from the hole. Large clods and soil chunks should be broken up as much as possible. Adding water during backfilling can help remove air pockets and better DIGGING moisten the roots. Dig a saucer-shaped hole wider than the root system but no deeper than the MULCHING root mass. Most holes do not need to Mulch individual trees with a 2-4” be deeper than about one shovel’s depth layer of wood mulch extending from (10-14”). The bottom of the hole should the trunk to at least the drip line of the be firm enough to prevent the tree from tree. Where possible, mulch trees and settling deeper after planting. Note: Us- other plantings together en masse to help ing an auger is not recommended since separate from surrounding turf. Don’t trees often settle too deep and the sides pile the mulch deeply over roots or of the holes become glazed. If using an against the base of the trunk and don’t auger, don’t drill deeper than needed and mulch with rock or use plastic weed Be part of it! loosen the sides of the hole. barriers under the mulch. PLANTING STAKING AND BRACING Join the Plant so that the base of the trunk Brace the tree if it might dislodge Nebraska statewide is at original ground level or slightly or blow over in the wind (most trees higher. The first lateral roots should typically benefit from staking). Some Arboretum end up just under the soil surface (1-2” sway should be allowed in the tree Your membership dollars stay in the deep) and the trunk should flare visibly after staking. Use only broad, belt-like state, and 70 percent of funding flows at ground level. materials to attach the bracing to the back into Nebraska’s communities. n Always locate the first main lateral trunk to help prevent rubbing injuries. roots and remove any excess soil above You receive garden-related Do not brace with wire, rope or wire them before setting the plant in the hole. publications, discounts on books, through hose. Remove staking within The first main roots are often several inches one year. prints, notecards and plants and free below the top of the container or root ball. admission to more than 100 botanical gardens and arboreta across America. Member Categories Individual Member...... $35 Post-planting Care and Other Information Family...... $40 WATERING n Address major soil problems before Patron...... $100 After planting, keep the root zone planting. Adding organic matter to the Associate (group)...... $100 moist but not waterlogged. In general, a planting site before planting can be very Contributor ...... $250 newly planted tree should receive about 1” beneficial for poor, inorganic and/or Sustainor ...... $500 of moisture per week, including rainwater, compacted soils. Benefactor ...... $1,000 during the first growing season. Check the PRUNING (circle member category desired) root zone frequently for moistness—don’t Before planting a container-grown tree, examine just guess. Many trees are lost to either At planting time, prune only to the root system carefully and remove any excess Name ...... under- or over-watering. Containerized trees remove dead or damaged branches and potting soil and/or root massing above the trunk to correct structural defects. Never Address ...... flare. often need more watering than bare-root or cut back healthy branches or trim the City ...... For container-grown trees, it is important to try B&B stock, because the porous growing to straighten any roots found growing in a circle. medium they are potted in dries out faster. tree to try and “balance” the top with State/zip ...... If the roots cannot be carefully pulled straight, the roots. The tree will benefit from Telephone ...... the root mass will likely need to be vertically FERTILIZING having as many food-producing leaves scored (cut) in three or four places around the If the right tree was selected for the left on as possible. Also, try to leave Email ...... root mass. planting site, fertilizer is generally not lower branches on a tree for as along as F Send Research Consortium catalog Nebraska tree enthusiasts and a properly planted needed. If fertilizer is desired, use only possible after planting. Lower branches tree in Cheyenne, Wyoming. From left: Dave a slow-release, low-nitrogen fertilizer help protect the trunk from cracking, Return to: Mooter (Kennard), Lyle Minshull (North Platte), applied to the soil surface after planting. sunscald and animal damage and they Justin Evertson (Waverly), Chip Murrow (Lincoln), Nebraska Statewide Arboretum n Never add fertilizer to the planting George and Gayla Probasco (Arapahoe), Deb aid in developing good trunk taper. If P.O. Box 830715 Henderson (Hemingford). hole since it can damage newly needed, limb the tree up gradually over University of Nebraska transplanted roots. In addition, excess a matter of several years after planting. Lincoln, NE 68583-0715 nitrogen in the soil can cause newly Monitor the tree when young and 402/472-2971 planted trees to add top growth at the prune, sparingly but properly, to prevent expense of proper root development. structural defects.