Essay, Pages 8 (1803 words)
To design well with trees we first need to understand the ecosystem that they naturally grow in. There are many different types of forest and savanna ecosystems across the world, all having distinct environments, climates, species and even aesthetic qualities. Nebraska is not exactly known for its forests but we have some interesting forest pockets, primarily made up of deciduous trees. Forest composition is determined by climate, terrain and availability of light (forest interior vs. forest edge) and of water (upland or lowland).
In our region of the world, these elements play a significant factor in both the diversity of species and the aesthetics. Terrain influences moisture availability and microclimates so different plant communities inhabit the low areas (linden, pawpaw, birch) and north and eastern slopes than the more drought-tolerant species, like bur and black oak, which tend to grow on ridge tops and on south- and west-facing slopes. Proximity to forest edge also influences plant communities. Forest edges occur along areas of disruption such as rivers, creeks, prairie edges, roads and paths.
Light is plentiful in these edge environments, which allows for a greater diversity of plant life. Some of the most fascinating elements of the forests that stretch through the Midwest occur along forest edges where prairie plants intermingle. My favorite juxtapositions are where prairie grasses like Indiangrass and little bluestem, and perennials like the sharp yucca, grow right up to forest edge, at times weaving their way in between trunks if the light is sufficient. Lesson 1: “Right tree, right place.
” While we can’t re-create the forest in our landscapes, we can apply lessons learned from the forest ecosystem to them. Our landscape composition should be influenced by terrain, climate, light and water availability, just as it is in the forest. We have all heard the phrase “Right tree, Right place,” but have you thought about that phrase through a biological lens? There are questions we can ask to help guide us. What is your climate like? What kind of site do you have? Is it protected? Is it wide open? Are there terrain variations which make sloped areas drier and low areas wet? Are there existing trees or other features? How you answer these questions will help guide species selection and overall design. Lesson 2: Forests contain layers. Using the concept of forest layers to drive our design helps us create aesthetically pleasing and ecologically functional landscapes. Consider using a mixture of largegrowing trees, understory trees, shrubs and herbaceous material. Lesson 3: Canopy is important. The forest canopy is comprised of large-growing trees. Regionally it is comprised predominantly of oak (Quercus); hickory (Carya); linden (Tilia); ash (Fraxinus); sycamore (Platanus); hackberry (Celtis;); and of course our mighty cottonwood (Populus). Heading west, diversity of these species diminishes and gives way to ponderosa pine forest. Heading east into Iowa and southeastern Nebraska, maples become part of the mix. Canopy trees provide protection for the plants growing beneath their branches. Forests are cool environments as a result of the shade and evapotranspiration of leaves. The tall, strong trunks and filtered light are visually interesting. In our landscapes, canopy trees act as a ceiling, give scale to structures, frame views and even act as a screen, depending on the
size of the property. Large trees also provide a myriad of other benefits. Placing a large-growing tree on the west and south side of a house provides substantial cooling benefits. Large trees, both evergreen and deciduous, protect from the wind an especially important function on open and rural properties. When large trees are used in more urban settings, such as street trees, their leaves also capture a substantial amount of stormwater. Lesson 4: Small trees need protection. Smaller statured trees, growing 15-30 feet high, make up the understory of the forest. Here the smaller trees such as redbud, serviceberry and pawpaw thrive in protected, partially-shaded conditions in and among larger trees. Their interesting leaf textures, form and bloom make these spaces change through the seasons. Many ornamental landscape trees, such as magnolia and dogwood that are native to the U.S. but not to Nebraska, grow in these understory environments. Looking at how understory trees naturally grow, it makes sense that they should be used in more protected environments. Their smaller stature visually connects the canopy trees and gives us a more comfortable sense of scale. There are more practical benefits as well. Understory trees, especially those with rounded canopies, low-branching and/or multi-stems, provide visual screening. It is important to note that some of our smaller-growing trees, such as crabapple and hawthorn, prefer more light and are naturally found in more scrub or edge conditions where light is plentiful. Lesson 5: In forested areas, trees grow in communities. The forest is made up of plant communities that include shrubs and herbaceous material. Coralberry (Symphoricarpos) and currant (Ribes) are common shrubs in Nebraska woods. One of my favorite understory shrubs, creeping mahonia, grows natively in our ponderosa pine forests, making a dense, deep green mat below the towering straight pine trunks. Sun-loving species such as American plum are found on the forest edge.
Lesson 6: Landscapes are dynamic through the seasons. From spring ephemerals to the deep rust, yellow and crimson foliage of fall, forests are always changing. A walk through the early spring woods takes careful stepping not to tread on the delicate green foliage rising from the leaf duff. It is here, in the early spring months, when the herbaceous layer of the forest does its magic. Spring ephemerals like Jack-in-the-pulpit, Virginia bluebells and others come to life before the forest layers above them set leaf. They grow, bloom, fruit and go dormant before the dry summer months and dense shade sets in. The same spot a few months later can be a cool and shady refuge in the dog days of summer and by fall long shadows, pools of light and fall foliage will light up the woods. Landscapes change and we need to embrace these seasonal changes and biological cycles of plants. Lesson 7: Landscapes change. Tree growth and disturbance influence the plant communities that can grow underneath them. In nature there are successional plants that over time give way to a more mature and established forest. In the same way, we have to anticipate the future growth of our landscapes as well as current conditions. For example, a common mistake is to plant woodland plants in and among new trees, where the current site conditions are sunny and
hot. Instead, we need to plant sun-loving plants and transition them over time to more shade-tolerant plants. In the same vein, perhaps you have very mature shade trees. Are you planting for the future? What happens when there is a “forest disturbance”? Will there be trees to replace these trees or will the plant community need to change? Lesson 8: No cool-season turfgrasses underfoot Once again, we can’t re-create the forest, but we can take some steps that help with the long-term survivability of our trees. None of the trees in forests are surrounded by carefully-clipped cool season grasses. Landscapes are always more successful when you can incorporate trees into larger landscape beds. This gives separation from turfgrass and also allows you to manage the bed differently. Allowing leaf litter to decompose adds organic matter and gives a place for beneficial insects to overwinter. Lesson 9: Diversity Not everything in our landscapes needs to be native, but our native forests and prairies give us a rich palette of plants that are adapted to Nebraska’s climate so consider buying trees grown from regionally native seed sources whenever possible. Christina Hoyt, Nebraska Statewide Arboretum Executive DirectorPollinators need a habitat rich in native food sources, with access to water and shelter and protection from chemicals. This may not sound like your typical Nebraska lawn but creating pollinator habitat doesn’t necessarily mean a complete garden makeover. Here are some simple ways you can make your yard more pollinatorfriendly. Provide Water Sources Small insects have a difficult time drinking from open water. Some pollinators get most of the liquid they need from drinking nectar while others need a water source. Bird baths or other vessels with a brick or rough rock for landing makes water more accessible for pollinators of all sizes.
Nesting Habitat It’s easy to think about pollinators in summer when flowers are blooming and bees are buzzing, but what do they do the rest of the year? A few species migrate south for the winter but most are with us yearround and survive the cold temperatures by hibernating as adults (like the bumblebee) or as larvae and eggs. Including space for all types of hibernation is a critical part of creating pollinator habitat. To provide space for ground-nesting insects like bumblebees and mining bees, simply leave small bare areas. For carpenter and leaf cutter bees, leave grasses and hollow-stemmed perennials where they can overwinter. Decaying branches and snags offer shelter for beetles and flies. Butterflies and moths can hibernate as caterpillars in plant debris at the base of grasses and perennials. Delaying garden cleanup until mid-April may help preserve as many nests as possible, and even then you may want to leave 6-12 inches of stem still standing.
Creating Habitat for Pollinators Protection from chemicals Protection from chemicals is one of the most important parts of creating a successful pollinator habitat. If you provide all the qualities they look for in a home but don’t protect the area from pesticide use, it can become a death trap. It’s best to limit use of lawn chemicals and place pollinator habitat in areas where you can avoid using insecticides and herbicides. To avoid drift from nearby, you may want to use signage and start friendly conversations with neighbors about what you are doing. Food from Spring to Fall Native flowers are rich in pollen and nectar. Research shows that native plants are four times more likely to attract adult pollinators than non-natives. In addition, many pollinator larvae feed from only a specific or very narrow range of host plants. So include native plants in your landscaping, especially larval host plants and ones that flower throughout the year. And don’t forget grasses. As well as being part of a balanced garden, native grasses are larval hosts for many species of butterflies, skippers and Spring-blooming Plants O Large Beardtongue, Penstemon grandiflorus O Wild Columbine, Aquilegia canadensis O Pasque Flower, Pulsatilla patens O Dwarf Spiderwort, Tradescantia tharpii Summer-blooming Plants O Purple Poppy Mallow, Callirhoe involucrata O Culver’s Root, Veronicastrum virginicum O Virginia Mountain Mint, Pycnanthemum virginianum O Rose Milkweed, Asclepias incarnata O Little Joe Pye, Eupatorium dubium ‘Little Joe’
Fall-blooming Plants O Aromatic Aster, Symphyotrichum oblongifolium O Wild Senna, Senna hebecarpa O Pitcher Sage, Salvia azurea Grasses O Indiangrass, Sorghastrum nutans O Little Bluestem, Schizachyrium scoparium O Blue Grama, Bouteloua gracilis Sarah Buckley, Bloom Box Program Coordinator