Thymus Praecox Creeping Thyme Albiflorus Veronica X (Alpina V

Final Report Identification, Utilization and Maintenance of Weed Suppressive Ground Covers Along New York Highways for Vegetation Management

Leslie A. Weston and Andrew F. Senesac With assistance provided by: Jennifer Allaire, Seok Hyun Eom, Roselee Harmon and Irene Tsontakis-Bradley Cornell University Department of Horticulture and Cornell Cooperative Extension Service of Suffolk County at Long Island Horticulture Research and Extension Center June 2004

Table of Contents

Page Number Introduction 2 Field Experiment 1 3 Field Experiment 2 10 Field Experiment 3 16 Greenhouse Stress Experiments 18 Roadside Evaluations 24 Changes in Protocol 28

Introduction:

The cost of vegetation management along New York State’s roads and highways results in expenditures of millions of dollars annually, for herbicides, mowing and hand labor in particular. New York State has been a leader in development of environmental policy for protection of its water and land resources for years. Recent public concern over the use of pesticides in municipal and state properties has resulted in the development of legislation since the year 2000, limiting municipal application of pesticides, including herbicides, in several locations across the state, including Suffolk and Nassau counties on Long Island, Westchester county and Erie county. Declining resources and an increased interest in management strategies with limited environmental impact have also reinforced the need to examine alternative strategies for vegetation management along New York State’s highway system. Effective alternative strategies could result in significant savings in terms of herbicide application, and further enhance their widespread adoption across the Northeast. To date, greatest vegetation management problems are encountered in highway medians and alongside roadways where guide rails are often encountered. Mowing is not always an option for weed management, especially under guide rails. Organic approaches for weed management including insect, pathogen and chemical application have been assessed in numerous landscape and a few roadside trials conducted by the authors, and have generally not been proven effective, with limited control observed (Bertin and Weston, 2003). In other studies conducted in recent years by the NY State DOT, trials involving landscape fabrics, mulching materials and certain organic products for weed suppression suggested that these alternatives were often expensive and not considerably effective for vegetation management along roadsides (NY State DOT reports). One potential option that has been underutilized in the U.S. and requires further consideration is the evaluation and utilization of weed suppressive, stress tolerant groundcovers which suppress annual and perennial weed infestations by providing a dense cover which competes for space, light, fertility, water and also inhibits weed growth by releasing natural herbicides, or allelochemicals from foliage or living root systems (Weston, 1996; Weston and Duke, 2003). Weed suppressive ground covers have been used effectively for years in orchards, vineyards, nurseries and vegetable fields. Less information exists about their utilization along roadsides in the temperate Northeastern U.S. In a site visit to Pennsylvania State University, we discovered that Pennsylvania DOT still considers use of crown vetch groundcovers for vegetation management along sloped roadsites, but in other states, this groundcover is considered less than optimal due to its ability to move offsite, unkempt appearance and difficulty to control. Fescues were also examined in Pennsylvania for use in roadside mixtures, with good results. In recent site visits to New Jersey, problems exist in development of high quality turf mixtures adapted to roadside conditions, including sandy soil sites, and enhanced vegetation management options are desired which would include selection of better adapted turfgrass mixtures for various state growing sites and optimal herbicide mixtures for effective management of difficult to control vegetation, including invasive species. Although the focus on environmental impact of herbicides in these states was less than in NY, roadside managers have expressed great interest in NY, PA and NJ locales in alternative, weed suppressive groundcovers, including newer cultivars of 3

turfgrasses, for lower maintenance inputs and achievement of better turf quality with reduced mowing requirements. Recent workshops conducted with NY State DOT personnel responsible for roadside vegetation management have also indicated great interest in alternative vegetation management strategies including selection of new groundcovers for roadside plantation (Weston, personal communication, 2004). This project was designed to select, evaluate and identify effective weed suppressive groundcovers, including herbaceous ornamental and grass species, which could be easily established under and adjacent to guiderails along NY highways, withstanding droughty conditions, infertile soils, winter road salts and other environmental challenges which might be encountered along roadsides. Experiments were performed from 2000-2003 in the field, laboratory and greenhouse research sites in 2 NY locations; Ithaca and Riverhead NY. In addition, roadside evaluation of selected groundcovers was performed at selected sites along NY State roadsides in 2003 in variable climatic and environmental conditions ranging from Long Island to upstate New York. Please note that all relevant data collected during the course of these studies will be presented in a large appendix file to the NY State DOT for future use. The quantity of data generated was considerable and due to the size of this dataset, we cannot present all of this in verbal form, but instead have chosen to present a summary document accompanied by a comprehensive data appendix.

The following table (Table 1) summarizes where and when major studies were conducted during the course of this project: Field study 1 Field study 2 Field study 3 Stress Roadside groundcovers groundcovers fine fescues Evaluation of Evaluation groundcovers groundcovers Ithaca NY Ithaca NY Ithaca NY Ithaca NY Ithaca NY 2000-2002 2002-2003 2001-2003 2003-2003 2003-2004 Riverhead NY Riverhead NY Riverhead NY Riverhead NY 2000-2002 2002-2003 2001-2002 2003-2004

Summary of Results from Field Studies Conducted in 2000-2003:

1. Field study 1 Field plots containing 21 species in Ithaca NY and 26 species in Riverhead NY were initially transplanted in September 2000, using 3 replications per treatment. Treatments consisted of the following 1) groundcovers that were weeded to establish 2) groundcovers that were weeded throughout the experiment and 3) groundcovers that were not weeded at all. All plots were allowed to initially establish by performing one hand weeding in early spring 2001. In 2001 and 2002 monthly data analysis included weed numbers per plot, weed biomass, time required for weed removal, light penetration of groundcover canopy, visual density of groundcover at the soil surface, and height of groundcover. This data was collected to clearly monitor both groundcover performance once established, and natural weed infestations resulting over time in each groundcover treatment. The following table provides a list of the species examined in studies performed in Ithaca NY and Riverhead NY in 2000-2002. These are the original species 4

proposed in our initial project description, and no variation in this initial selection occurred. Table 2. List of species evaluated in Field study 1 conducted in Ithaca and Riverhead NY from 2000-2002. Genus Common Name Cultivar Alchemilla mollis Lady's Mantle Carex morrowii Sedge Ice dance Fragaria x Flowering Strawberry Lipstick Houstonia serpyllifolia Bluettes Hydrangea anomala Climbing hydrangea peteolaris Hypericum calycinum St. Jonhswort Hypericum moseranum St. Jonhswort Mix Tricolor Imperata cylindica Japanese blood grass Red Baron Lamiastrum galebdolon Yellow Archangel Herman's Pride Liriope spicata Liriope Leymus arenarius Blue Lyme Grass Blue Dune Lysimachia nummilaria Moneywort Aurea Mazus reptans Mazus Nepeta x faassenii Cat mint Walker's Low Phlox subulata Creeping Phlox Emerald Blue Phuopsis stylosa Phuopsis Sedum reflexum Sedum Blue Spruce Solidago sphacelata Dwarf Goldenrod Golden Fleece Thymus praecox Creeping thyme Albiflorus Veronica x (alpina v. alba x spicata) Speedwell Goodness Grows Vinca minor Vinca

The species planted in Riverhead, Field Study 1, Fall 2000 were: Achillea tomentosa 'King Edward' Alchemilla mollis Arctostaphylos uva-ursi 'Pt. Reyes' Carex morrowii 'Ice Dance' Chrysogonum virginianum 'Pierre' Fragaria x (F. ananassa x Potentilla palustris) 'Lipstick' Houstonia serpyllifolia Hydrangea anomala 'Peteolaris' Hypericum calycinum Hypericum x moserianum Imperata cylindica 'Red Baron' Lamiastrum galebdolon 'Herman's Pride' Leymus arenarius 'Blue Dune'* Liriope muscari 'Royal Purple' Liriope spicata 'Majestic' Lysimachia nummularia 'Aurea' Mazus reptans Miscanthus sinensis Nepeta x faassenii 'Walker's Low' Phlox subulata 'Emerald Blue' 5

Phuopsis stylosa Sedum reflexum 'Blue Spruce' Solidago sphacelata 'Golden Fleece' Thymus praecox 'Albiflorus' Veronica x (alpina v. alba x spicata) 'Goodness Grows' Vinca minor.

(*Note: We have found this species to be an aggressive spreader by rhizome. It is potentially weedy and/or invasive. It should be used with caution and only in sites where it can be contained.)

A. Ithaca Results

Species which did not overwinter: Five species including Hydrangea anomala, Hypericum calycinum, Hypericum moseranum, Imperata cylindica, and Phuopsis stylosa, did not overwinter successfully in Ithaca NY, apparently due to their inability to tolerate cold winter conditions and relative lack of hardiness. These species died almost completely during the winter of 2000-2001 and were therefore not included in further evaluations in the field. Poorest performing species: The majority of groundcovers listed in Table 1 were ranked as poor to moderate performers in 2001-2002 field seasons, in terms of ability to form a dense, closed canopy with limited light penetration and ability to suppress weeds. Limited light penetration of the canopy proved to be important in reducing weed infestation, as light is important in stimulating germination of many annual weeds at the soil surface, and is also an indicator of the density and overall vigor of the groundcover evaluated. Several groundcovers which were judged to be the poorest performers in 2001-2002 included: Fragaria x, Houstonia serpyllifolia, Lysimachia nummillaria, and Leymus arenarius. Fragaria (ornamental strawberry) exhibited a bacterial disease on its foliage, which we were unable to further identify. Species described as poor performers did not produce dense canopy coverage after 2001 or 2002, and all treatments of these species were infested with large numbers of weeds. In contrast to Alchemilla mollis, our best performing species in Ithaca NY, Liriope spicata was one of the poorest performers and exhibited approximately 10 to 100 times greater number and biomass of weeds per plot when compared to Lady’s Mantle. Best performing species: Only five groundcovers were described as successful performers after 2002, 2 years after establishment in field settings in Ithaca NY. These successful performers included Alchemilla mollis, Nepeta x faassenii, Phlox subulata, Solidago sphacelata and Thymus praecox. We judged these groundcovers to be successful due to their dense canopy formation, lack of insect and disease infestation, and strong weed suppressive abilities, as evidenced by few weeds collected from established plantings in 2001 or 2002. Groundcovers which were the best performers in our studies were attractive in appearance, with both interesting foliage and inflorescence, were resistant to droughty soil conditions, and required no particular maintenance to reestablish in year 2, such as trimming or defoliation. Alchemilla mollis (Lady’s Mantle) was the generally the top-rated species as far as weed suppression in terms of lowest weed number and least weed biomass encountered in any weeding treatment. Results obtained for Nepeta x faassenii and Phlox subulata were similar to Alchemilla mollis with 6

regards to time required for weed removal, light penetration, and visual density of soil surface covered by the groundcover. Nepeta was covered with bright blue flowers for most of the growing season, and remained attractive, despite a taller growth habit. Nepetas as well as other members of the mint family are known to produce a number of bioactive volatile terpenoids which may contribute to weed suppression through allelopathic effects of its foliage. Phlox was a low growing groundcover which flowered only in early spring, but the dense, low-growing canopy remained an attractive green during the rest of the growing season. All of the successful groundcovers established canopy coverage early in the season and weed growth was thus suppressed, as light was prevented from reaching the soil surface to stimulate germinating weeds and groundcover biomass was highly competitive, preventing additional growth of established weed seedlings. Thymus praecox was one of the middle ranked low-growing groundcovers in 2001 and 2002, until mid-summer when it rapidly spread and developed excellent coverage of the soil surface. This species tends to grow well when it is exposed to dry, full sun conditions and was most competitive in year 2. Solidago sphaceolata and Sedum retroflexum also performed well in our experiments, although their canopy coverage was not as dense as the aforementioned species.

Riverhead Results Twenty-six herbaceous perennial and woody groundcover species were planted in the field into Riverhead Sandy Loam in September 2000. Details regarding plot design and layout are contained in Appendix A. Additional details including dates, procedures, and data for this study can be found in Appendices B, C, F, and J.

As in Ithaca, each groundcover species was subjected to three weed management regimes or treatments consisting of either: (1) maintaining plots completely weed free throughout the season by hand weeding (Weed Free, WF), (2) maintaining plots weed free for the first half of the first growing season to allow crop to establish (Weed to Establish, WE), or (3) performing no hand weeding at all (Weedy, WY).

Data collected in Riverhead on a regular basis during the course of the two year study (growing season 2001 and 2002) included: (1) visual assessment of percent cover of the crop and of the weeds, (2) light penetration reduction through the crop canopy, and (3) amount of time needed to hand weed.

These data were chosen to predict how each species would perform in a real roadside planting. The greater the percent cover and light reduction exhibited by a species, the greater ability it would have to suppress weed growth. The time it takes to weed is an indicator of both the type, size, and number of weeds infesting the groundcover and a predictor of labor required for maintenance.

Species which did not overwinter In the Spring of 2001, winter survival was evaluated and four species were eliminated for the inability of the newly planted material to successfully overwinter in this location (Plant Hardiness Zone 6). These were: Hypericum calycinum 7

Hypericum x moserianum Miscanthus sinensis Phuopsis stylosa

By the end of the first growing season (Fall 2001), eleven of the twenty-two remaining species had covered the ground by 80 percent or more in the hand weeded treatments. These species also reduced light penetration to the soil surface by at least 75 percent. For the most part these same species were the least weedy and had the greatest percent ground cover as well. These species were: Alchemilla mollis Carex morrowii 'Ice Dance' Chrysogonum virginianum 'Pierre' Fragaria x 'Lipstick' Leymus arenarius 'Blue Dune' Liriope muscari 'Royal Purple' Liriope spicata 'Majestic' Nepeta x faassenii 'Walker's Low' Phlox subulata 'Emerald Blue' Solidago sphacelata 'Golden Fleece' Thymus praecox 'Albiflorus'.

During June of 2002, four additional species were planted into Field Test 1, including: Delosperma nubigenum Rubus calycinoides (syn. pentalobus) Rubus tricolor x R. fockeanus 'Betty Ashburner'.

All data collected throughout the two seasons was analyzed in several ways to obtain an overall Weed Suppressiveness Rating of “Good”, Fair”, or “Poor” for each species. Data from the second year was given slightly more weight because if the species was successful the second year but not the second, long-term success would be diminished. Species exhibiting high percent cover, greater light reduction, and short duration weeding time were the more successful species.

Best performing species By the end of their second growing season (Fall 2002), six species had emerged from the previous season’s list of eleven top performers as outstanding in their weed suppressive ability. Through evaluations of ability to cover the ground in both hand weeded and non-hand weeded treatments, in their reduction of light transmittance, and in their ability to suppress weeds through two growing seasons (see Table below) these six species were determined to be the best performers. Their performance had been unaffected by winterkill, diesease, or insect infestation.

Groundcovers given a Weed Suppressiveness Rating of “Good” were: Alchemilla mollis Leymus arenarius Liriope spicata ‘Majestic’ Nepeta x faassenii 'Walker's Low' Phlox subulata 'Emerald Blue', and Solidago sphacelata 'Golden Fleece'.

Table 3. Results from Riverhead regarding weed suppressivity of groundcovers in 2002.

Poorest performing species overall: Species that received a Weed Suppressiveness Rating of “Fair” were: Carex morrowii 'Ice Dance' Chrysogonum virginianum 'Pierre' Fragaria x (F. ananassa x Potentilla palustris) 'Lipstick' Liriope muscari 'Royal Purple' Mazus reptans Sedum reflexum 'Blue Spruce' Thymus praecox 'Albiflorus' Vinca minor.

Species that received a Weed Suppressiveness Rating of “Poor” were: Achillea tomentosa 'King Edward' Arctostaphylos uva-ursi 'Pt. Reyes' Houstonia serpyllifolia Hydrangea anomala spp. peteolaris Imperata cylindrica 'Red Baron' Lamiastrum galebdolon 'Herman's Pride' Lysimachia nummularia 'Aurea' Veronica x (alpina v. alba x spicata) 'Goodness Grows'.

The second season replacement species were rated as follows: Rubus tricolor x R. fockeanus 'Betty Ashburner' Good Delosperma nubigenum Fair 9

Rubus calycinoides (syn. pentalobus) Fair.

Native NY species evaluation: In addition, a separate demonstration trial of selected native species was to be conducted in 2001-2002 in Ithaca and Riverhead NY. We proposed to evaluate an extensive list of native species to be direct seeded into research plots. After much searching on the internet and in seed catalogues, we discovered that most of these species were not readily available by seed or purchased plant materials. In some cases, seed was too expensive to purchase for large plot work. In other cases where seed was purchased, it never germinated. Therefore, we established an additional demonstration garden in Ithaca NY for observational purposes only. These plots were generally not replicated due to lack of propagated material or seed for planting, but were evaluated for their ability to densely establish rapidly and suppress weeds, nonetheless. From the demonstration trial, several species emerged as drought tolerant selections which achieved reasonable ground coverage in a relatively short period of time. These included Sedum alba ‘Acre’. Eight cultivars/species of low- growing sedum were evaluated in this study in Ithaca NY. Of the direct seeded species obtained, Potentilla arbuta, wild white potentilla and crested wheatgrass (Agropyron desertorum), a direct-seeded, hardy perennial species suitable for roadside mixtures in the Midwestern US, also performed well.

B. Summary of Results in Ithaca and Riverhead for Field Study 1 Based on these studies conducted in Riverhead and Ithaca NY from 2000-2002, the following 6 candidates were selected for further study for their ability to overwinter in several climatic zones, suppress weeds in heavily infested field situation (based on weed infestation numbers and weights), and exhibit reasonable aesthetic appeal. In addition, we wished now to determine if these same 6 species would tolerate roadside stresses in a greenhouse setting (task c), and actually perform well in roadside trials in 2003 and 2004 (tasks e and f).

Table 4. Selection of species for use in roadside and salt stress experiments based on superior field performance in 2001 and 2002: Scientific name Common name Cultivar Alchemilla mollis Lady's Mantle Nepeta x faassenii Cat mint Walker's Low Phlox subulata Creeping Phlox Emerald Blue Sedum reflexum Sedum Blue Sprucea Solidago sphacelata Dwarf Goldenrod Golden Fleece Thymus praecox Creeping thyme Albiflorus

The overall best performing species in both Riverhead and Ithaca NY in 2001 and 2002 field conditions in terms of appearance, weed suppression and stress tolerance were the following:

-Alchemilla mollis or Lady’s mantle -Phlox subulata or creeping phlox ‘Emerald blue” -Nepeta x faassenii or catmint ‘Walker’s low’

C. Summary of Tasks Completed

The following table (Table 5) summarizes tasks completed with completion of field study 1 in Ithaca and Riverhead NY: Task a Task b Task d Task e Selection, Field experimental Interim reports were Selection of species propagation and evaluation presented in 2001 for final roadside establishment of completed in 2002 and 2002 with site testing made in species completed visits in summer 2002 in 2000 2002 and 2003

2. Field Study 2

In Ithaca and Riverhead NY, a field experiment was established in 2002-2003 to further evaluate a number of low-growing ornamental groundcovers that were propagated mainly by seed (with a few propagated by cutting). Groundcovers were grown in a greenhouse in either Ithaca or Riverhead NY in 2002 for several months during their propagation period, until they were hardened off outdoors and transplanted in Ithaca or Riverhead NY in late May 2002 in field experiments. Much of the seed obtained for these species was purchased from Jellito Seed Company in West Germany. Following extensive rainfall in May 2002, the field sites were prepared and plants transplanted by hand. Treatments again included groundcovers to be evaluated under 3 different weeding regimes for each groundcover: 1) weed regularly throughout the course of the experiment 2) weeded until establishment of a canopy cover (generally 1 month following transplanting) and 3) unweeded for the course of the experimental period. Data collected was similar to that obtained for field study 1 and included: weed number and weight collected per plot at the end of the season, light interception at the soil surface under each groundcover treatment, time required for handweeding each groundcover in treatment 1, and visual estimation of groundcover biomass for each treatment. Twenty-two herbaceous perennial and woody groundcover species were planted in the field into Riverhead Sandy Loam in May 2002 and 25 in loamy silt soil in Ithaca NY. Details regarding plot design and layout are contained in Appendix D. Additional details including dates, procedures, and data for this study can be found in Appendices F, G, and J.

Table 6. List of species evaluated in field study 2 in Ithaca NY containing low-growing, stress-tolerant groundcovers in 2003-2004.

Genus Common Name Cultivar Aurinia saxatilis Basket- of - gold Dianthus deltoides Dianthus, maiden pink 11

Dianthus myrtinervius Carnation pink Erigeron glaucus Beach fleabane Erigeron karvinskianus Bonytip fleabane Gypsophila cerastoides Baby’s breath Gypsophila repens Creeping baby’s breath Lavandula augustifolia English lavender Minuartia verna Sandwort Petroghagia saxifraga Saxifrage tunicflower Potentilla nepalensis Nepal cinquefoil Silene uniflora Double bladder campion Stachys byzantina Lambsears Trifolium repens Purple dutch clover Veronica prostrata Creeping speedwell Veronica repens Harewell speedwell Arabis caucasica Rock cress Carex pennsylvanica Early sedge Heuchera americana Coral bells Chocolate veil Lavandula hybrida Lavender Mentha x piperita Black peppermint Phlox stolonifera Creeping phlox Rhus aromatica Fragrant sumac Vaccinium macrocarpon American cranberry Cerastium tometosum Snow in summer

The species planted in Riverhead, Field Study 2, Spring 2002 were: Aubrieta deltoidea Aurinia saxatilis 'Gold Dust' Carex pensylvanica Cerastium tomentosum Dianthus deltoides 'Brilliant' Erigeron karvinskianus 'Blutenmeer' Gypsophila cerastioides Heuchera Americana 'Chocolate Veil' Mentha x piperita* Minuartia verna Nepeta subsessilis Oenethera pallida Phlox stolonifera 'Sherwood Purple' Rhus aromatica 'Gro Low' Silene uniflora (syn. maratima) Silene caroliniana Solidago cutleri Stachys byzantina Thymus serpyllum 'Suffolk County'* Trifolium repens 'Atropurpureum' Vaccinium macrocarpon Veronica repens. 12

(*Note: We have found this species to be an aggressive spreader by rhizome or seed. It is potentially weedy and/or invasive. It should be used with caution and only in sites where it can be contained.)

A. Ithaca Results. Species which did not overwinter: Several species proved to be difficult to establish in Ithaca NY. In 2002, a droughty summer was encountered with abnormally high temperatures early in spring and late summer. In 2003, a wet and cool summer was experienced. Snow cover in 2002 was adequate. Species which had difficulty in overwintering included Minuartia verna, Lavandula spp., Trifolium repens, Gypsophila repens and Arabis caucasica. Best performing species: Data collected included weed number, weed biomass, light penetration of the canopy, visual estimate of canopy spread over the soil surface and groundcover biomass. Despite heavy weed infestation in Ithaca and less weed infestation in Long Island, results were somewhat similar in both locations in that several groundcover species emerged as top performers. In Ithaca NY, both dianthus species were excellent performers, as was Stachys byzantina (lambsears), Mentha x piperata (mint) and Heuchera americana (coral bells), and Rhus aromatica. These exhibited excellent coverage of the soil surface, were fast-growers in terms of biomass produced, had no disease problems and suppressed weeds effectively. These groundcovers were all relatively low-growing, achieving heights of less than 20 cm generally. Aurinia saxatilis, Thymus serpyllum (wild thyme) and Nepeta subsessilis (dwarf catmint) were also excellent performers. Aurinia exhibited disease problems in Ithaca in 2003, but dwarf catmint and wild thyme were very good performers in demonstration evaluations at this location due to excellent canopy formation. Additional demonstration plots were performed in 4 landscape settings across NY State in association with county extension offices. Sites for evaluation included western NY, central NY, capitol city district, and Nassau county. Species evaluated in these sites included Dianthus deltoides, Dianthus myrtinervius, Stachys byzantina, Mentha X piperita, Heuchera americana, Arabis caucasica, Veronica prostrata and Trifolium repens. All species performed well in sites with adequate fertility and low weed infestation. In areas of higher weed infestation, including Nassau county, Dianthus deltoides, Heuchera americana and Stachys byzantina were best performers. Poorest performing species: Our observations in both Ithaca locations, however, suggested that the taller groundcover selections performed better in sites which were heavily infested with weeds. All low growing species required at least one initial weeding to establish effectively. Without weeding, most short groundcovers in this experiment were not competitive with weeds and many plants either died or were significantly stunted in growth. Stachys byzantina in year 2 of field experimentation in Ithaca dropped in status as a top performer after flowering. Unfortunately, this species produces an elongated, upright inflorescence which fell on the plant and decomposed following flowering, leading to unattractive appearance and less effective weed suppression. Mowing or trimming of this species before or after flowering would be a wise suggestion for maintenance.

Riverhead Results: 13

By the end of the first growing season (Fall 2002), eleven of the twenty-two species had covered the ground by 80 percent or more in the hand weeded treatments. Most of these species also reduced light penetration to the soil surface by at least 90 percent. For the most part these same species were the least weedy and took less time to weed. These species were: Aurinia saxatilis 'Gold Dust' Cerastium tomentosum Dianthus deltoides 'Brilliant' Erigeron karvinskianus 'Blutenmeer' Mentha x piperita Nepeta subsessilis Oenethera pallida Silene caroliniana Stachys byzantina Thymus serpyllum 'Suffolk County' Veronica repens.

Through the end of the 2002 growing season and into the Spring of 2003, four species were eliminated and no further data was collected. Two species were destroyed by disease by the end of 2002 and had little or no reemergence the following spring. These were: Oenethera pallida Silene carolinian.a One plant was eliminated for the inability to successfully overwinter in this location (Plant Hardiness Zone 6): Erigeron karvinskianus 'Blutenmeer'. And one plant was severely browsed by wildlife: Trifolium repens 'Atropurpureum'.

Best performers: By the end of their second growing season (Fall 2003), six species had emerged from the previous season’s list of eleven top performers, as outstanding in their weed suppressive ability through evaluations of ability to cover the ground in both hand weeded and non-hand weeded treatments, in their reduction of light transmittance, and in their ability to suppress weeds through two growing seasons (see Table below). Their performance had been unaffected by winter-kill, diesease, or insect infestation. These species, given a Weed Suppressiveness Rating of “Good”, were: Aurinia saxatilis 'Gold Dust' Heuchera americana 'Chocolate Veil' Mentha x piperita Nepeta subsessilis Stachys byzantina Thymus serpyllum 'Suffolk County'.

Poorest performers: Species that received a Weed Suppressiveness Rating of “Fair” were: Aubrieta deltoidea Dianthus deltoides 'Brilliant' Erigeron karvinskianus 'Blutenmeer' Gypsophila cerastioides Rhus aromatica 'Gro Low' 14

Silene uniflora (syn. maratima) Solidago cutleri Trifolium repens 'Atropurpureum'.

Table 7. Results from Riverhead regarding weed suppressivity of groundcovers in 2003.

Species that received a Weed Suppressiveness Rating of “Poor” were: Carex pensylvanica Cerastium tomentosum Minuartia verna Oenethera pallida Phlox stolonifera 'Sherwood Purple' Silene caroliniana Vaccinium macrocarpon Veronica repens.

Field Demonstration in Riverhead

Eight broadleaf perennial and six grass groundcover species were planted in the field into Riverhead Sandy Loam in May 2002. This demonstration field planting was not replicated (only a single plot of each species was planted). Details regarding plot design and layout are contained in Appendix E. Additional details including dates, procedures, and data for this study can be found in Appendices F, H, and J. 15

All perennial groundcover species were maintained weed free by hand weeding throughout the season.

Each grass species were subjected to three planting and management regimes: (1) planted by sowing seed in the field with no herbicide use and early first-season hand weeding to establish crop (seed), (2) planted by sowing seed in the field with herbicide use (Tupersan at 6.0 lb./ac a.i.) to facilitate establishment and early first-season hand weeding to establish crop (seed/chem), and (3) planted as established plugs transplanted into field and hand weeded throughout season (trans).

Data collected during the course of the two year study (growing season 2002 and 2003) included: (1) visual assessment of percent cover of the crop and of the weeds, (2) amount of time needed to hand weed, and (3) biomass (fresh weights) of weeds.

The species planted in Riverhead, Field Demonstration, Spring 2002 were: Broadleaves: Alchemilla mollis 'Thriller' Arabis caucasica Arenaria montana Gypsophila repens Iberis saxatilis Potentilla nepalensis 'Shogran' Silene saxifraga Silene uniflora 'Compacta' Grasses: Agropyron cristatum Calamagrostis canadensis Elymus canadensis Koleria cristata Schizachyrium scoparium Sporobulus heterolepsis.

B. Summary of Results for Ithaca and Riverhead Field Experiment 2: The best performing species in 2002 and 2003 were those that exhibited tallest growth habit in this collection of low-growing groundcovers. Those that performed best in field conditions under high levels of weed infestation and exhibited stress tolerance to both wet and droughty field conditions besides aesthetic appeal included: - Dianthus deltoides - Stachys byzantina - Heuchera Americana - Rhus aromatica - Mentha x piperita - Nepeta subsessilis - Thymus serpyllum 'Suffolk County' 16

For these reasons, these species were selected for further evaluation in 2003-2004 in roadside and landscape demonstration trials.

C. Summary of tasks completed:

The following table (Table 8) summarizes tasks completed with completion of field study 2 in Ithaca and Riverhead NY:

Task a Task b Task d Task e Selection, Field experimental Interim reports were Selection of species propagation and evaluation presented in 2002 for final roadside establishment of completed in 2003 with site visits in testing made in species completed summer 2002 and 2002 in 2002 2003

3. Field Experiment 3.

In 2001, we established 1 x 1 meter square plots of each of the above fescue cultivars in both Ithaca and Riverhead NY. Seed was direct seeded to prepared plots in spring of 2001 at a 4 lb/ 1000 sq. ft rate. Ratings were collected in 2001 and 2002 growing seasons and included weed suppressivity and quality of turfgrass. Treatments evaluated included non-weeding and weeding provided by herbicide treatment and handweeding where necessary. Ratings were collected on a monthly basis in Ithaca NY. Herbicide treatment was applied by postemergent application of Confront to control broadleaf weeds only in Ithaca, and use of pre and postemergent herbicides in Riverhead to control both broadleaf and grass weeds.

A. Results in Ithaca and Riverhead:

Best performers: In both locations, 3 cultivars emerged as superior performers in terms of early establishment and ability to suppress weeds in unweeded conditions. This was particularly evident in year 2001, just following establishment. Superior performers included Oxford, Reliant II and Intrigue due to their lush establishment, lack of weeds and good color and uniformity. All superior cultivars established a dense turf and suppressed weeds exceptionally well, and by year 2, herbicide treatment to selectively remove weeds was not generally required for good weed suppression. Superior cultivars exhibited attractive green coloration and appearance in 2001 and 2002.

Poorest performers: In Ithaca NY, poorest performers included Treazure and Boreal, due to less than uniform establishment and weediness. We observed similar trends in another 3 year cultivar evaluation performed as part of the National Turfgrass Evaluation Program.

Table 9. Selected fine fescue (Festuca rubra) cultivars evaluated for weed suppression in 2001 in Ithaca NY. Attila Sandpiper Treazure Intrigue Jasper Boreal Columbra Oxford Reliant II Rescue

B. Summary of Results: Superior fescue performers in terms of weed suppressivity, uniform establishment and green color included:

- Intrigue - Oxford - Reliant II

In laboratory assays, these cultivars also demonstrated superior allelopathic or weed suppression in agar bioassays with commonly occurring weed species in turfgrass including white clover, dandelion, annual bluegrass, large crabgrass and barnyardgrass.

C. Summary of tasks completed:

The following table (Table 10) summarizes tasks completed with completion of field experiment 3.

Task a Task b Task d Task e Selection, Field experimental Interim reports were Selection of species propagation and evaluation presented in 2002 for final roadside establishment of completed in 2002 with site visits in testing made in species completed summer 2002 2002- 2003 in 2001

4. Experiment 4. Stress Evaluation of Groundcovers in Greenhouse Setting

This experiment was designed and performed in Ithaca NY to evaluate the drought and salt tolerance of selected weed suppressive groundcovers in a greenhouse setting in order to predict ability to tolerate roadside stress conditions. Groundcovers evaluated included the following: Nepeta faassenii, Alchemilla mollis, Phlox subulata, Solidago sphaceolata, Thymus praecox, and Sedum alba. These groundcovers were selected based on past success in field experiment 1 with respect to overwintering, ability to suppress weeds and tolerate many environmental stresses.

Tolerance to salt stress was evaluated by application of aqueous solutions of NaCl applied at various concentrations ranging from 0 to 400 mM NaCl. Most species require at least 100 mM salt to exhibit noticeable salt stress. Salt solutions were applied daily, leached the following morning by application of clear tap water and reapplied following drainage of water to ensure consistent water and salt availability throughout the course of the experiment. These concentrations were selected to simulate average roadside salt concentrations,made readily available to groundcovers during spring months when rainfall, snow melt and leaching of salt-infused water might occur along NY roadsides.The following parameters were measured for each species evaluated over 5 replicates per species: electrical conductivity of soil to assess how much salt was present after treatment, daily water loss as salt stress is often a reflection of plant water loss, plant biomass at the termination of experiment, the level of abscisic acid in leaf samples of each species, and salt content of plant leaf tissue. Abscisic acid is an indicator of water stress in higher plants and production of ABA is often associated with various plant stress factors. ABA analysis was performed in the laboratory using gel electrophoresis and immunochemistry (response to antibodiesto ABA in collected samples) to assess ABA concentrations using a sensitive but rapid analytical procedure.

Tolerance to drought stress was measured as well by subjecting these same species to numerous days of water stress by not watering plants over a week long time course. Differential response to both salt and drought stress was observed, depending on species evaluated.

Soil Electrical Conductivity

Preliminary Test Result after 20 days

16000 7000

add as much as losing water 6000 cont treat after washing by water alch 12000 add fully 5000 nepe standard phlo 4000 sedu 8000 S) soli icroS) icro 3000 thym cti vit (m y ndu Co onductivity (m 2000 C 4000

1000

0 0 control 50mM 100mM 200mM 400mM 0 50mM 100mM 200mM 400mM

Salt concent ration (mM) Salt concentration

A. Results:

With increasing salt concentration applied to greenhouse soils, salt levels measured in treated soils increased in a linear fashion, regardless of the manner in which salt solutions were added to the soil medium. Since most roadside salt in NY State is applied as NaCl pellets, NaCl solutions applied daily were used as treatments for salt tolerance experiments. Each species evaluated in greenhouse growth medium accumulated increased NaCl with increasing concentration applied.

The following represent pictorially the effects of salt and drought treatments upon each species evaluated in greenhouse experiments under controlled environmental conditions: Alchemilla mollis 6 days after treatment

0 mM 400 mM Drought 20 days after treatment