Effectiveness of mixed perennial groundcovers in establishing hazelnut hedgerow systems in the Northeast

Nutwood Farm | Cummington, MA

Project Summary

Perennial groundcovers play a critical role in the forest ecosystem, yet are rarely employed on farms modeling ecological agricultural practices.  This project will evaluate the effectiveness of different combinations of woody and herbaceous perennial groundcovers as compared to a perennial living mulch “cover crop” and non-living woodchip mulch in establishing a hazelnut (Corylus spp.) hedgerow system.  The groundcovers in the study have been selected for low and spreading  growth habits as well as their ability to accumulate nutrients, build soil and attract beneficial insects.  By trialing different combinations of these plants in four distinct patterns or “guilds,” we hope to demonstrate ways to maximize the production area of a hedgerow system while delivering the most ecological benefits in an integrated productive nut farm.

Over the course of the three-year study (2018-2020) we will measure groundcover growth in hedgerows and interspecific effects.   Each fall, we will collect soil and hazelnut leaf tissue samples from plots for nutrient and soil health analysis.  We will measure the height and girth of hazelnut leader canes and root sprouts to determine groundcover system affects on growth of hazelnuts.  Finally, we will observe population trends of beneficial insects.  Results of the study will be shared via an on-farm field day, a presentation at a NOFA-MA Winter Conference, and in a published article.  The project will greatly benefit small and mid-size nut and fruit orchards across the region, and contribute to the knowledge base around adapting critical permaculture techniques for ecological restoration and climate stabilization at the farm-scale.


 What is the problem and why is it important?

Agriculture systems have evolved over thousands of years to maximize the size and productivity of a select number of edible plants for our consumption.  The recent development of annual agriculture by means of regular soil tillage, monocropping, and chemical fertilizers has led to massive losses in the available nutrients and fertility of some of the most productive soils on the planet.  Short term economic incentives and a lack of understanding around the biological soil food web has created a dearth of nutrients in our food crops and a host of pest and disease problems that increasingly must be managed with ever-stronger biocides and genetically modified organisms.  Instead of continuing down the path of decreasing ecological health, many organic and alternative farmers are turning toward polycultural and diverse perennial deciduous agriculture systems to produce food in ways that restore and enhance soil health and ecological resilience.

There are many challenges in developing new systems of management in ways that will aid incremental transition efforts from annual to perennial agriculture; chief among these are concerns around establishment costs and comparatively lower yields during the establishment phase.  Machine cultivation and harvesting are also more complicated in diverse perennial systems, requiring either more specialized equipment or more hand labor.  Researchers at the Badgersett Research Farm are working to develop mechanical management options for large-scale commercial production of woody crops such as hazelnuts, chestnuts, and hickories for food, biomass, and oil production.  However, there is still unexplored potential for smaller scale production of these crops in integrated orchards and farms.

The greatest challenge we have faced in establishing hazelnuts in a swale-and-berm hedgerow system is the need to manage and suppress the vigorous forest regrowth out of which the hedgerows were created.  Weed management in hazelnut production is especially crucial for increasing nutrient availability, tree growth, and the efficiency of hand harvesting (Isık et al., 2014).  One key principle of permaculture is the maxim, “the problem is the solution.”  In our case, the inability to mow with tractors provides an opportunity to explore alternative groundcover management practices that could lead to better overall health and productivity.  Mulching with ramial woodchips has been our main strategy to date for covering the soil and maintaining a more fugally dominant soil microbial population.  The limiting factor however has been the continued application of fresh woodchips for weed suppression in a large planting.  We also seek to improve nutrient cycling and the structure and fertility of the soil to support a healthier, more diverse ecosystem and enhance crop growth and yields.  Living mulches, cover crops, and perennial groundcovers have all been shown to positively impact these factors, yet knowledge on the integration of these management techniques in perennial systems is still insufficient for wider adaptation.  More information is needed to better understand how intentional groupings or “guilds” of perennial plants can work together in a hedgerow system to achieve the goals of a holistic and more profitable management strategy.


What is your project’s objective?

The objective of our project is to determine if using select herbaceous and woody perennial groundcovers during the establishment of hazelnut (Corylus spp.) shrubs in hedgerow plantings will decrease weed pressure competition and increase the growth and nutrient composition of the hazelnuts as compared to a non-living mulch groundcover control.  Over the course of the study we will observe the spreading rates and growth habits of different combinations or ploycultures of perennial groundcovers.  We will also track growth rate of hazelnut canes as well as the soil organic matter and leaf tissue concentrations of nutrients (N, K, P, Ca, Mg, Fe, Cu, B, Mn, Z) over a three-year period.  If a perennial living mulch can be established successfully, the need for annual application of other organic mulch would be nearly eliminated, greatly reducing the associated labor and costs of current hedgerow maintenance. We hypothesize that if well-selected for complimentary traits, these understory plants would function together to better accumulate and cycle nutrients, build soil organic matter, decrease insect pest pressure, increase pollinator and predatory insect populations, and ultimately increase productivity.


 What efforts have been made by others to solve the problem/take advantage of this opportunity?

Alternative groundcover management systems have been developed by a number of commercial orchardists seeking better organic weed control techniques that improve soil nutrients and fruit yields without the negative side effects of chemical herbicides (Lipecki and Berbeć, 1997)(Teasdale, 1996).  Several studies suggest that planting cover crops as living mulch between orchard trees can greatly reduce weed density, the number of weed species, and total weed dry biomass (Isık et al., 2014)(Mennan, et al., 2006).  Furthermore, the use of cover crops have been found to not only control weeds but also improve soil fertility, improve soil structure, and enhance crop growth and yield (Farooq et al., 2011).

Many different groundcover management systems have been studied in orchards including mechanical cultivation, sward strip-planting, and organic and synthetic mulches.  In one study, natural (hay, wood chips, recycled paper pulp) and synthetic (polypropylene film and polyester fabric) mulches were compared with mechanical tillage and residual herbicides as orchard groundcover management systems in two New York apple orchards (Merwin, et al., 1995).  The researchers found that soil concentrations of K, P, NO3 and Mg were greater in natural mulches.   In another study, total soil N and C, C-to-N ratios, other essential plant nutrients, and overall apple tree growth were also greater in wood chip mulch after 16 years (Atucha et al., 2011).  Others have also found groundcover management systems to have increased the species richness, abundance, and diversity (H′) of arthropods, even when used with frequent pesticide applications (Sirrine et al., 2008).

While these studies point to promising results – higher nutrients and healthier soils – by reducing the use of herbicide and tillage in perennial orchard systems and increasing the use of organic mulches and cover crops, less is known about the effects of establishing woody perennial groundcovers as part of a holistic groundcover management system.  Much of this research is still preliminary, anecdotal, or theoretical, and has lacked significant enough data to warrant larger scale studies or trials.  Some reasons may include the potential interference of woody perennials in mechanical management or harvesting on large scale commercial farms, or the assumption that perennial groundcovers may overly compete with primary trees and shrubs and be difficult to manage long term.  However, there is some evidence that with careful selection, perennial groundcovers can significantly enhance the health of an orchard and reduce or nearly eliminate the need for the frequent cultivation, mowing, or mulching of conventional orchard management systems (Phillips, 2011).

While there is little research available on comparative hazelnut guilds, the general principles of guild design can be applied to assess plant compatibility and achieve certain results.  The design of effective plant guilds draws primarily on observations made in naturally-occurring forest environments.  A  guild is defined as a “group of species with dissimilar community niches that form networks of mutual aid” (Jacke and Toensmeier, 2005).  The functional interconnection between different species (for example, nut trees and squirrels) lead to systems of mutual support and interdependence, something that is observable in all diverse ecosystems.  In addition, whenever multiple species occupy the same community niche and share the available resources, the resulting redundancy can help maintain the stability of the system and even use “more resources more fully by exploiting more niches” (Jacke and Toensmeier, 2005).  For instance, a fruit and nut guild designed by Weiseman et. al. includes spearmint, wild ginger, and violets in the understory of pear, almond, and fig trees (Weiseman et. al., 2014).  Ben Falk at Whole Systems Research Farm in VT favors comfrey, alliums, blue false indigo, and mushrooms beneath his fruit trees (Falk, 2013).  Michael Phillips adds to that a combination of lovage, horseradish, daffodil, and lemon balm (Phillips, 2011).

At New Forest Farm in Wisconsin, Mark Shepard demonstrates how the productive potential of all niches in an ecosystem can lead to a very profitable enterprise.  Even if the species in the guild are not all edible for humans, they can still perform a number of useful functions such as providing fodder, nectar, wildlife habitat, mulch, medicine, and essential oil and fixing nitrogen or accumulating other macro/micronutrients from the subsoil below (Weiseman et. al, 2014).  Moreover, research suggests that the understory vegetation of a forest, despite its limited biomass, accounts for a disproportionately high percentage of nutrient concentrations and nutrient cycling, further highlighting their usefulness when incorporated into perennial agricultural systems (Muller, 1978).  This suggests there is ample potential, in both health and in productivity, in studying the potential application of perennial groundcovers in a holistic hazelnut orchard management system.


What will your project’s methods, measurements and timeline be?


The project will be conducted with three different experimental perennial groundcover polycultures in addition to a control plot, which will remain in woodchip mulch throughout the duration of the study, reapplied at 2″ depth annually and hand-weeded.

The four plots will be randomly assigned in 30′ sections beneath newly planted hazelnut seedlings in two new hazelnut rows, each approximately 300 ft long, with hazelnuts planted on 3 ft centers for a total of 200 hazelnuts.  Each plot will therefore incorporate 10 hazelnuts.

The three polyculture designs will be planted with distinct combinations of perennial groundcovers in a consistent pattern.  As perennial plants can be more difficult to germinate by seed, they will be grown out for 8-weeks in a nursery in flats of 72s and transplanted into the field in early May 2018.  Each of the three experimental polycultures will have different objectives.  Pattern A will prioritize soil building and mineral accumulation, Pattern B will focus on providing beneficial insect habitat and nectary sources, and Pattern C will maximize nitrogen fixation.

Pattern A: Mineral Accumulators
Fieldmint Mentha arvensis
Peppermint Mentha x piperita
Catmint Nepeta mussinii
Comfrey Symphytum officinale
Chive Allium schoenoprasum
Garlic chives Allium tuberosum
Yarrow Achillea millefolium
Pattern B: Beneficial Insect & Nectary
Oregano Origanum vulgare
Mountain mint Pycnanthemum spp. muticum
Aromatic aster Symphyotrichum oblongifolium
Tick seed Coreopsis verticillata
Plumbago Ceratostigma plumbagenoides
Bigfoot geranium Geranium macrorrhizum
Wild violets Viola spp.
Pattern C: N-Fixers
Perennial lupines Lupinus perennis
Dutch white clover Trifolium repens
Red clover Trifolium pratense
Birdsfoot trefoil Lotus corniculatus
Common vetch Vicia sativa

These plants were selected based upon suitability for perennial polyculture.  These include height, growth habit, shade tolerance, nectar production, flowering time, beneficial insect habitat, nutrient cycling potential, edible or medicinal qualities, and potential income generation (see Table 1).  The final guild designs will be reviewed by an expert consultant prior to planting to ensure high likelihoods of plant compatibility.



The measurements for the project will assess a number of variables to determine the success of each groundcover guild.  The growth rate and spread of the plants in the trial groups will be assess for the individual diameter of each species and the percentage of ground successfully covered between the hazelnuts.   Observations will also be recorded on the interactions between the plants in each guild in terms of growth habits, flowering time, and potential competition.

In order to assess the effect of groundcovers on hazelnut growth, we will measure height and circumference of the central leader 3 times per year, in spring after planting, midsummer, and fall.  The number of new root sprouts beneath each hazel will also be counted each fall.  Because the hazelnuts used in this study are seedlings with diverse genetics carefully selected from superior unnamed parent varietals, it may not be possible to correlate hazelnut growth with groundcover treatments.  However, this data may still prove useful for tracking overall trends.

Lastly, the effects on soil and hazelnut plant nutrients will be measured with soil and leaf tissue tests each spring (April 30) and fall (October 31).  The soil samples will be tested by Logan Labs, LLC using their AEA Base Test Plus, which measures electrical conductivity, Mo, Co, Se, and Si in addition to the standard macro- and micronutrients of soil chemistry.  Leaf tissue samples will be sent to UMass Soil and Plant Tissue Laboratory for analysis.  Because hazelnuts take 3 years to begin bearing, nut yields will not be used as a measurement in this study.

Throughout the duration of the study we will dedicate 4 hours per week (May-October) to collect data, perform maintenance as needed to mow weeds, brambles and stump sprouts in the control plot and adjacent to the trial plots, and monitor pest and beneficial insect species to assess suitability of guilds in supporting desirable species.


What is the outreach plan? 

There is a great deal of interest in our local and regional food system around the potential for increasing the home and commercial production of nuts and other perennial crops in woody agricultural systems.  In order to communicate the progress and results of our research, we intend to host a field day in collaboration with CISA (Community Involved in Sustaining Agriculture) in the Fall of 2020.  These events typically draw 30-40 beginning and experienced farmers to visit other local farms and learn about diverse topics in farm and business management.  In addition to hosting and presenting our SARE research, we will work with CISA to identify another presenter to join us for the day and broaden the topics covered in the session for wider appeal.

We will also present our project-in-progress at the NOFA Winter Conference in Worcester, MA in January 2020 in a 90-min workshop session.  This conference reaches a wide audience base from all over the region interested in sustainable agriculture.  Last year’s conference was attended by over 900 farmers, gardeners, students, researchers, extension agents, and concerned citizens.

Finally, after all the data is compiled and analyzed, we will submit an article to variety of relevant publications, such as the Northern Nut Growers Association The Nutshell, the UMass Amherst Fruit Notes, the NOFA Natural Farmer, and the internationally known Permaculture Research Institute’s online blog (