A GUIDE to HEDGEROWS: Plantings That Enhance Biodiversity, Sustainability and Functionality

OREGON STATE UNIVERSITY EXTENSION SERVICE Photo: Justin Smith, © Oregon State University An aerial photo taken above Forest Grove shows hedgerows bordering the urban growth boundary and used as buffers between fields. A GUIDE TO HEDGEROWS: Plantings That Enhance Biodiversity, Sustainability and Functionality P. Monnette and J. Hobbs fences “hagas” or hedges, from the word “hawthorn.” As the birds settled in the hawthorns and dropped seeds, e see them at the edges of farm fields or along more plants sprung up. Today, many farms in England roads: long rows of trees, shrubs, flowers and are surrounded by ancient hedgerows that shelter Wgrasses known as hedgerows. They are living beneficial organisms and conserve soil and water. fences with the ability to grow food, shelter wildlife, save Hedgerow plantings were uncommon in the early water, manage weeds and look beautiful all year round. United States. In the 1930s, the U.S. Department of Hedgerows are sometimes called shelter belts, Agriculture’s Shelterbelt Program briefly supported windbreaks or conservation buffers. These layers of plant planting trees for windbreaks to prevent soil erosion in the life enhance the beauty, productivity and biodiversity of Midwest. Today, as interest surges in sustainable farming a landscape. methods, more people are turning to this age-old practice. Hedgerows originated in medieval Europe and are enjoying a modern resurgence. People in England Pamela Monnette, agriculture outreach program coordinator, Lincoln planted hawthorn cuttings and allowed them to grow County, Oregon State University Extension; Jude Hobbs, executive to about 6 feet. They were bent and trained to fill gaps director, Agro-Ecology Northwest and Cascadia Permaculture, and in the trees, yielding a living fence. They called these founding member, Permaculture Institute of North America. EM 8721 Revised June 2020 Photo: Janet Donnelly, © Oregon State University This young hedgerow bordering a field features native plants that provide habitat for beneficial insects and pollinators. Hedgerows can serve several ecological functions. perches for raptors, which are important predators Among their many benefits, hedgerows: of rodents. Dense or thorny shrub thickets can offer songbirds a refuge to escape predators as well as a • Enhance ecological biodiversity. place to nest. The diverse composition and structure of • Offer food for livestock, humans and wildlife. a hedgerow creates a functional habitat where species • Provide habitat for beneficial insects and experience vital interconnections with one another and pollinators. the environment. • Facilitate water conservation. • Provide windbreaks. Offer food for livestock, • Help manage invasive weeds. humans and wildlife • Provide erosion control and improve soil health. Hedgerows provide undisturbed refuge for species • Support the health of aquatic habitats. of all kinds, creating wildlife corridors, travel lanes or habitat islands. Hedgerows help protect wildlife from • Enhance carbon sequestration. predators and provide sheltered access to riparian • Create borders and privacy screens. zones or other water sources. These corridors are • Reduce noise, dust, chemical drift and other especially important in fragmented landscapes, such types of pollution. as fields where only a single crop is grown. Hedgerows • Diversify farm income. provide shade to reduce heat stress and help to block wind currents. These measures support a healthier • Generate year-round beauty. wildlife population. Berry-producing plants encourage Let’s look at these benefits in detail. insectivores, such as birds, that also prey upon common crop pests. The hedgerow habitat creates Enhance ecological biodiversity cover for wildlife so they can feed, nest and care for their young. Biodiversity describes the variety of life forms within a specific ecosystem and the relationship of these organisms to one another and the broader Provide habitat for beneficial insects environment. Hedgerows can be designed to attract a and pollinators wide variety of mammals, birds, reptiles, amphibians, Planting a variety of flowering trees, shrubs, forbs insects and plants, many of which offer beneficial and perennial plants provides insect habitat, and nectar relationships to each other. They also create more and pollen sources throughout the year for beneficial edges, or “ecotones,” between different habitats, which insects and pollinators. Plants in the family Umbelliferae increases species diversity. Trees and shrubs provide attract parasitic wasps; predator flies such as hover shelter for larger mammals, and nesting sites and flies, lacewings and ladybeetles; and true bugs, like 2 ambush or minute pirate bugs. Flowering plants in this Provide erosion control family include coriander, dill, fennel, parsnip, parsley and carrots. These plants are useful in the kitchen and improve soil health and are also very attractive to pollinators. Over 75% Rain, irrigation, clean cultivation and vacant field of successful production of food requires pollination. borders can all increase erosion potential in an Increasing plant habitat for pollinator species improves agricultural system. fruit set, size and quality, as well as general biodiversity. Hedgerow plantings can significantly reduce Pollinator habitat also attracts beneficial insects, which the amount of soil erosion on a landscape. They prey on many crop pests. Increasing the numbers of can also provide a barrier to filter out pollutants, beneficial insects can help farmers manage crop pests such as pesticides, and slow down sediments and and cut down on insecticide use. organic material that can flow from farm fields into waterways. This is accomplished by increasing Facilitate water conservation the surface water infiltration rate and improving Hedgerows retain water and reduce evaporation soil structure around the root zone. This, in turn, by reducing wind speed and providing cover over the decreases fertilizer runoff from farm fields. The ground surface. Plants also catch and store water in their biomass that plants shed acts as a soil conditioner root systems, leaves and branches, slowing the rate of and can enhance plant growth. In urban or suburban excess rainwater entering waterways and reducing the environments, hedges similarly reduce pollutants risk of flooding. Decaying matter from the roots, stems from neighboring sites. and branches of hedgerow plants increase the organic matter in the soil over time. This increases the soil’s Support aquatic habitat ability to absorb and retain water. Planting hedgerows Hedgerows can provide shade to riparian areas. on hillsides helps conserve water and soil by reducing Shade reduces water temperatures, prevents water erosion. If planting near adjacent cropland, periodic root evaporation and improves watershed quality. Though pruning can reduce competition for nutrients and water. many factors influence watershed temperatures, studies have proven that lowland streams bordered by trees and tall shrubs exhibit cooler temperatures. The Provide windbreaks hedgerow’s latitude, stream aspect, leaf density and Properly designed hedgerows can reduce wind speed the height of its vegetation from the water surface all by as much as 75% and improve crop performance. This affect water temperature. is especially effective when plantings reach a density of 40%–50% and are planted perpendicular to the prevailing wind. Wind-resistant trees usually have flexible, wide- Enhance carbon sequestration spreading, strong branches and low centers of gravity. During photosynthesis, trees, shrubs and grasses Wind-tolerant shrubs often have small, thick or waxy absorb carbon dioxide from the atmosphere, leaves or very narrow leaves or needles, to help control allowing the carbon to become part of the plant’s moisture loss. Wind can disturb pollination and damage tissue. As plants die or shed tissue — either through fruit and flowers when plant parts thrash against each natural processes or pruning — the carbon that was other. During times when soil is exposed, a windbreak stored in the plant breaks down and enters the soil. can protect topsoil from erosion. Crops under wind stress Plants store relatively large amounts of carbon in also put energy into growing stronger roots and stems, their biomass, helping to offset some of the effects resulting in smaller yields and delayed maturity. Strong of climate change. A tree can absorb as much as winds also cause lodging of grain and grass crops, bending 48 pounds of carbon dioxide per year and can the stems and making harvest more difficult. Winds dry sequester, or store, 1 ton of carbon dioxide by the out crops on the field edges, increasing pests such as two- time it reaches 40 years old. spotted spider mites. Create borders and privacy screens Help manage invasive weeds along roads and between properties Hedgerows planted along roads or between crop Hedgerows are attractive borders and can block fields may prevent weed seeds from blowing into the undesirable views. Evergreens offer year-round field. The weed seed pods collect on hedgerow plants, screening. When selecting plants, consider the height where a farmer could remove and burn them. Hedges at maturity for optimum screening. Evergreens can be can prevent millions of weed seeds from entering pruned to control height and density. Plant a diverse the crop field. As hedgerows mature, these plantings mix of species to help protect against damage from a displace invasive weeds. If well maintained,

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