Abstract
There has been a continuing disparity between what urban foresters say they request for community plantings and the stock availability from nurseries. To investigate this, twenty-two of Ohio’s urban foresters were surveyed in February 2008 to contrast their planting needs with nursery stock availability. Urban foresters reported planting more than 9,000 trees in 2005 and expected to plant more than 15,000 trees in their respective communities in 2010. At the same time, nearly 278,000 trees [5 cm (2 in)] were reported as being available for sale by nurseries participating in the 2008 Ohio Nursery Stock Survey. The results suggested that maples, crabapples, many hawthorns, and pears generally were present in nurseries in excess of the quantities desired by urban foresters. Conversely many legumes, oaks, elms, lilacs and lindens were lacking in availability. Several other species were somewhat balanced in terms of urban foresters’ requests and nursery production. Ohio, U.S. has been dealing with the impacts of the emerald ash borer on Fraxinus species. Increasing taxonomic diversity can be a relatively low cost means of insuring against the possible introduction of another exotic pest that might attack another genus (such as Acer) and requires increased availability of some species currently lacking in availability in the nursery supply chain.
- Acer
- Community Planting
- Crataegus
- Fraxinus
- Gleditsial
- Malus
- Nursery Stock Availability
- Pyrus
- Quercus
- Tilia
- Ulmus
A commonly reported paradox has been heard when talking with urban foresters and nursery producers in the state of Ohio, U.S. Urban foresters claim they cannot get the plants they desire for planting on community streets, in parks, or in other public spaces, and must settle for second or third choices. Nursery producers, in contrast, claim that they will produce anything customers wish if they become aware of a demand. In order to bridge the gap between trees desired by urban foresters and those available from producing nurseries in the state, surveys of urban foresters were taken in 1995, 2000, and 2008. Summary results were published in the Buckeye (the official publication of the Ohio Nursery and Landscape Association), so that results would be available to the Ohio nursery community (Sydnor 1996; Sydnor et al. 2000; Sydnor 2008).
Some nurseries have responded and are growing some previously requested plants but many urban foresters find they are still unable to get their first choice in plant material. Another part of the puzzle would be to compare what is being requested with what is actually available for sale in nurseries. Nurseries have had information on what was requested in the 1995, 2000, and 2008 surveys, but neither the urban foresters nor nurseries have had a feel for the supply side of the equation. This study seeks to address this problem.
The impact of emerald ash borer (EAB) has reinforced the need for increased diversity in urban forests. Communities often try to limit a single species to 10%, a genus to 20%, and families to 30% (10-20-30 rule or guideline) of the trees in their forest (Santamour 1990). Using these criteria, many Ohio communities are too heavily planted in maple and pear. For example, some Ohio community public spaces have been found to contain more than 30% maple (Sydnor and Subburayalu 2008a; Sydnor and Subburayalu 2008b). Ohio’s original shade tree evaluation project, which included 97 community plantings, found 27 of the plantings (28%) were maple (Sydnor et al. 1999).
A 2007 survey of urban foresters suggested a potential economic impact of EAB in Ohio communities at USD $2 to $8 billion (Sydnor et al. 2007). Furthermore, about 8% of community forests in Ohio are in ash species, while maples are in excess of 30% (Sydnor and Subburayalu 2008a). Given that maple abundance is approximately four times greater than ash abundance, the statewide community impact might reach $8 to $30 billion if a similarly devastating exotic pest of maple were to strike. Biological diversity is a relatively inexpensive way to deal with the threat of exotic pests, especially when compared to removing and replacing trees. While these examples relate specifically to Ohio and the Midwest, other regions in the United States and even other countries have imbalances they must consider as well (McBride 2008). The southeastern U.S., for example, depends too heavily on oak species while other regions have different imbalances.
Previous surveys of nursery stock needs have concentrated on urban foresters with the results published in literature available to the nursery producer. However, if urban foresters had some notion of what might be available, they could seek additional suppliers, encourage existing suppliers to produce material that might not be available, grow some material themselves, or develop contracts for plants to be produced in the future. Columbus, Ohio, expanded its own nursery in the 1990s to produce plants for out planting as a result of the inability to gain the desired mix of plants (Low 2008). Existing nursery stock surveys are designed for an individual to identify a grower from whom a given plant might be secured; they convey information to outlets marketing to the final user but are not designed to provide information to upstream segments in the supply chain—such as liner or seedling producers—who are likely to be in other states. To this end, a survey of existing nursery stock relative to current and anticipated needs by urban foresters for community plantings would be useful. The objective of this study was to identify differences between what was requested by urban foresters and what nurseries offer for sale and to provide a means for a community forester to begin a dialog with potential suppliers to provide less commonly grown trees for use on community streets.
MATERIALS AND METHODS
In February 2008, fifty-nine e-mail surveys were sent to all of Ohio’s urban foresters on the Ohio Division of Forestry’s community urban forester mailing list. The survey instrument was similar to those used in previous years (Sydnor 1996; Sydnor et al. 2000; Sydnor 2008). Responses could be returned by e-mail, FAX, or postage mail. A follow-up survey mailing was not conducted. A total of twenty-two responses were returned for a 39% response rate. Responses were received from all areas of the state and all community size classes.
Urban foresters were asked to identify, from a predetermined list on the survey form, how many trees of a species were planted in 2005 and how many plants of the same species were expected to be planted in 2010. The original list contained more than 200 species of trees that might be planted on Ohio streets. Of the plants listed on the survey form, responses were given for 183 taxa. Plants requested one or more times for either 2005 or 2010 were identified for comparison with the nursery stock survey. Plants not requested by urban foresters but grown by Ohio nursery producers were not evaluated. Respondents were asked for contact information in case follow-up questions were needed. Appendix 1 shows an abbreviated survey instrument with the first five lines presented.
In March 2008, permission was obtained to access the online version of the Ohio Nursery Stock Survey (Anonymous 2008). Table 1 gives an example of a portion of a stock survey entry. Nursery stock entries are reported by taxa, grower, plant size, production method (container or field), and quantity. Individual records were created for each nursery, 5 cm (2 in) size, production method, and taxa, with an associated quantity code. Quantity codes in the nursery stock survey represented ranges, such as 50–100 plants. The range mid-point, 75 in this example, was entered into the resulting database for further exploration. Family, genera and species codes were assigned by the investigators. All cultivars, size, production technique, and quantity counts were combined into a single species count. Information on grower was not carried into the evaluation. Counts thus represented the totals of all growers with 5 cm trees of a single genus and species (including all cultivars). There were a total of 277,856 trees listed for sale from the Ohio Nursery Stock Survey for 2008 in the 5 cm size class (as described in the next section, this was the plant size most commonly purchased by responding urban foresters).
An example of an Ohio Nursery Stock Survey entry for a given species. Grower codes are listed in the first column, and sizes in the remaining columns. Quantity codes for each grower are noted under the size headings with numeric codes given for container plants and alpha codes for B&B stock.
There were 9,279 trees planted in 2005 in the respondents’ 22 communities, and 15,333 requests for trees anticipated for planted during 2010. It was decided to normalize the data such that comparisons could be made between years and sources. Thus, in 2005, responding urban foresters planted 9,279 of the 277,856 trees available in Ohio nurseries (3.339% of the trees available). By multiplying the number of trees of a given species available in nurseries by 0.03339 (3.339%), one obtains the number of trees available to communities for planting. Then by subtracting the number planted in 2005 from the number available in nurseries, one gets a measure of the difference between available trees relative to planting needs. A positive number for a given family or species suggests an excess of trees in nurseries, while negative numbers indicate a shortage of plants available for communities from nurseries. Similarly, in 2010, there were 15,333 requests anticipated by responding urban foresters. The 277,856 trees listed for sale in the 2008 Ohio Nursery Stock Survey were again used as the nursery stock base. If one divides the 15,333 forester requests by 277,856 (trees available), one finds that 5.518% of Ohio nursery output will be requested by these communities for 2010.
RESULTS AND DISCUSSION
The survey of urban foresters showed that trees were normally purchased as 5 cm plants. Thus it was this size of plant for which quantities were recorded from the Nursery Stock Survey. Results contrasting nursery stock availability with urban foresters’ planting requests for 2005 and 2010 are reported at the family and species levels. After a review of the data, a cut-off of plus or minus 70 trees was selected for brevity of presentation in the species table (Table 2). As shown in Appendix 2, several species were somewhat balanced in terms of urban foresters’ requests and nursery production.
Total nursery availability (number of trees by species), number of trees available to responding communities, number of trees planted by responding communities, and difference between availability and plantings, 2005 and 2010. Trees with availability within +/− 70 trees are not shown in this table but are listed by scientific name in Appendix 2.
Family Level
The rose family had the greatest excess with 628 more plants available to communities than were requested in 2005 and with nearly 2,282 more available for 2010 (Table 3). Plants in the rose family are generally smaller flowering trees, such as crabapples and medium-sized Callery pears. Crabapples are often planted beneath utility lines and both crabapples and Callery pears are frequently planted in sidewalk cuts or smaller tree lawns. This will likely continue as crabapples and pears are among the only flowering trees capable of withstanding the environmental stress found in these planting sites. This also likely reflects the heavy demand for flowering trees in landscape applications.
Total nursery availability (number of trees by family), number of trees available to responding communities, number of trees planted by responding communities, and difference between availability and plantings, 2005 and 2010.
Whereas species from the rose family are smaller trees with reduced environmental benefits, maples are generally used as canopy trees. Most of the environmental benefits of trees in urban areas accrue to larger trees (Sydnor and Subburayalu 2008a); as a result, communities are often planting larger trees where the site allows. Toward this end, maple availability in Ohio nurseries exceeded what urban foresters wanted both in 2005 and 2010, by 536 and 1,178 plants, respectively. Maples have become popular street trees for a variety of reasons, including ease of clonal propagation, ease of transplant, shade, often vivid fall color, and marketing efforts by nursery suppliers. Further analysis in many cities, however, suggest canopy-sized maples are currently present in excess of the 10-20-30 rule (Santamour 1990). For example, maples constituted 50% of the street trees in Toledo, Ohio, and 37% of the trees representing 56% of the canopy cover in Xenia, Ohio (Sydnor and Subburayalu 2008a; Sydnor and Subburayalu 2008b). Based on the 10-20-30 guidelines, it would not be recommended to plant maples in Ohio’s public spaces unless or until community stocking levels are reduced below 20% to reduce the potential risk of an introduced exotic pest such as the Asian longhorned beetle that might attack maples (Fater 2008). In another study, when demand was expressed as percent market share, the demand for maples by urban foresters was expected to decline by almost two percentage-points from 2005 to 2010 (Sydnor 2008).
The Cornaceae, Hamamelidaceae, and Pinaceae families tended to be available in excess of quantities demanded by urban foresters. Pines and spruce are rarely used as street trees in Ohio, but commonly available due to demand for landscape plantings. Likewise, many plants in the dogwood family are forest understory plants and infrequently used on community streets.
Plants in the Betulaceae, Eucommiaceae, Fagaceae, Leguminosaea, Oleaceae, Platanaceae, Tiliaceae, and Ulmaceae families generally are lacking in availability. Seed sources are important for plants in the beech family, thus making propagation more difficult. For example, pin oak, a member of Fagaceae, is native and adaptable if grown from local seed sources in the higher pH of central Ohioan soils, but is prone to develop an iron deficiency if grown from seed plants adapted to an acidic soil region of the United States.
Genus and Species Level
When considering species, Acer palmatum (Japanese), A. platanoides (Norway), A. saccharum (sugar), A. × Freemanii (Freeman), and A. rubrum (red) maples demonstrated excess availability for both 2005 and 2010 (Table 2). Conversely, Acer campestre and A. truncatum maples were deficient in availability for 2005 and 2010, while A. buergeranum and A. ginnala maples supplies appeared to fall short of anticipated demand for 2010.
The projected lack of downy serviceberry may simply be a nomenclatural problem as Amelanchiers are often sold under more than one scientific name. Most cultivars seen in the nursery trade are Amelanchier × grandiflora but are sold under a variety of names.
Carpinus betulus (European hornbeam) was projected to be in limited supply for both 2005 and 2010. Interestingly, this plant has not done well in Ohio except in the colder areas (Sydnor et al. 1999). The senior author has observed this plan doing well north of Ohio. Hornbeam borer attacks plants in the warmer areas of Ohio.
Crataegus (hawthorns) establish but perform poorly in stressful urban sites, such as tree lawns, in Ohio (Sydnor et al. 1999), and now tend to be used in less stressful lawn panels or plant beds. Hawthorn hybrids were or are projected to be lacking in availability. Crataegus viridis, C. punctata, C. Phaenopyrum, and C. crus-galli inermis hawthorns are also utilized in landscape plantings with green and thornless cockspur hawthorn being available in excess of demand.
Ash (Fraxinus spp.) was an interesting situation with a warning as to the importance of taxonomic diversity. In February 2003, EAB was discovered in Lucas County, Ohio. In spring 2004, the landscape market for ash collapsed. Ohio communities planted few ash trees to fill in plantings or for special requests in 2005, and none were requested for 2010. The plant was not listed in the 2008 Ohio Nursery Stock Survey.
Gleditsia triacanthos inermis (thornless honeylocust) was deficient in availability for 2005 but in excess for 2010. Communities have been reducing the use of honeylocust as a street tree as it frequently damages sidewalks but performs well and rarely exceeds 10% of an Ohio community’s urban forest. If properly sited, this tree could be used more frequently. Some communities substitute Gymnocladus dioicus (Kentucky coffeetree), for honeylocust. This leguminous tree grows slowly in nursery production and has an open, irregular canopy making it unpopular with many growers thus explaining its limited availability in 2010.
Parrotia persica (Persian parrotia) and Phellodendron amurense (Amur corktree) are projected as deficient in availability for 2010 despite urban forester’s lack of experience with this tree. Communities looking for greater diversity are seeking these plants. This may represent a possible marketing opportunity for producers.
Platanus spp. were deficient in availability in 2005 and are projected to be so in 2010 as well. Communities favor London planetree (P. × acerifolia) for planting despite its being marginally cold hardy because of resistance to sycamore anthracnose, a common cosmetic disease. Sycamore (P. occidentalis), in contrast, has been variably sensitive to the cosmetic disease but resistant to cankerstain (often fatal to London planetrees in Ohio). Interestingly, if demand were expressed as an expected change in percent market share from 2005 to 2010, sycamore would be increasing slightly while London planetree would be diminishing (Sydnor 2008).
Prunus sp. (cherries and plums) were variable with some shortages in flowering cherries as communities seek alternatives to crabapples and pears. When considered as percent market share, cherries are generally decreasing in community demand (Sydnor 2008). Plums and cherries are more commonly seen in private landscapes rather than streetscapes.
Quercus spp. (oaks) are variable but generally lacking in availability, especially for 2010. Many nursery professionals prefer to grow clones and many oaks are difficult to propagate asexually. Additionally, many oaks take additional time to grow which adds to a nursery’s costs. Despite these challenges, oaks appear to be a real opportunity for nursery producers given the increasing interest from urban foresters.
Pekin (Syringa pekinensis) and Japanese (S. amurensis) tree lilacs are deficient in availability and increasing in demand as a percent market share (Sydnor 2008). They are being used as flowering trees but are small in stature and slow growing in tree lawns.
Lindens (Tilia sp.) are generally undersupplied with American (T. americana) and silver (T. tomentosa) being in highest demand. Again inaccurate nomenclature in this genus may factor in the results shown.
Elms (Ulmus sp.) are generally lacking in availability. Fast growth and urban tolerance are among the assets for elm species. Disease resistance has been identified for many serious problems, but some cosmetic concerns are present. Interestingly, lacebark elm (U. parvifolia) was one of the few elms decreasing in demand when expressed as change in percent market share (Sydnor 2008). Overall, availability fell short in this study for 2005 and 2010. Elm seems poised to be among the most popular species for landscape applications in another ten years.
CONCLUSION
Results from this study highlight the need for establishing stronger lines of communication between nursery stock suppliers and urban foresters. Requests for nursery stock by responding urban foresters were found to represent only 3%–5% of Ohio nursery production. Thus nurseries have many additional customers. Urban foresters must communicate with nursery suppliers and let them know what they will need and when they are satisfied with their services. The segmentation of the nursery industry into various components such as seedling production, whip production, wholesale producers, and brokers over the past decades has likely resulted in reduced prices for consumers. One of the casualties of segmenting the supply chain has been the limited communication between segments, especially those growers early in the production cycle and end users such as urban foresters.
Another difficulty arises when an urban forester requests an oak (309 shortfall for 2010), for example, but has to accept a maple substitute since oaks are not available from the successful bidder. The nursery then logs the substituted maple as a sale, using sales data in determining what to plant the following year. In this way, information regarding the original request might be lost and market disequilibrium can result. Some nurseries see this as a means of managing inventory. Still others are willing to work with customers to bring plants to market not currently in inventory; for several species, the quantities being demanded and supplied were somewhat balanced (Appendix 2).
Maples, crabapples, many hawthorns, and pears are generally present in nurseries in excess of what urban foresters demand. Some of these excesses represent plants being grown for other purposes such as pines for screening or Japanese maples for decorative purposes. Conversely, many legumes, oaks, elms, lilacs, and lindens are deficient in availability; such species likely represent plants purchased by Ohio community foresters from out-of-state sources. Urban foresters can increase taxonomic diversity by informing their preferred nursery suppliers of the plants they expect to purchase, ordering those plants, and not accepting substitutes when the low bidder says the plants are not available. This will increase the taxonomic diversity in their communities and in the nursery industry as well.
APPENDIX 1. AN ABBREVIATED SURVEY INSTRUMENT SHOWING THE FIRST FIVE ENTRIES OF THE ORIGINAL LIST THAT CONTAINED MORE THAN 200 SPECIES. THE HEADER AND THE FIRST TWO COLUMNS WERE FILLED OUT BY RESPONDENTS. THE REMAINING FOUR COLUMNS WERE USED FOR CODING AND TO IDENTIFY PLANTS IN THE SURVEY.
PLANTING SURVEY FORM
Insert the approximate number of trees planted in 2005 for each species that you planted in the first column. Insert the estimated number for each species you wish to plant in 2010 assuming no problems with availability.
Community___________________________ Phone No. __________________.
Expected number planted for 2010 __________________ Expected Size _______________.
APPENDIX 2. LIST OF TREES EVALUATED WHERE URBAN FORESTERS’ REQUESTS AND NURSERY PRODUCTION APPROACHED BALANCE (DIFFERENCES WITHIN +/− 70 TREES).
Acer circinatum
Acer griseum
Acer negundo
Acer nigrum
Acer pensylvanicum
Acer pseudoplatanus
Acer saccharinum
Acer tataricum
Acer truncatum
Aesculus glabra
Aesculus Hippocastanum
Aesculus octandra
Aesculus Pavia
Ailanthus altissima
Alnus glutinosa
Amelanchier × grandiflora
Asimina triloba
Betula alleghaniensis
Betula lenta
Betula nigra
Betula papyrifera
Betula pendula
Betula populifolia
Betula utilis
Carpinus Caroliniana
Carya cordiformis
Carya glabra
Carya illinoinensis
Carya ovata
Catalpa bignonioides
Catalpa speciosa
Celtis laevigata
Celtis occidentalis
Celtis reticulata
Cercidiphyllum japonicum
Chionanthus retusus
Chionanthus virginicus
Cornus alternifolia
Cornus Drummondii
Cornus florida
Cornus mas
Cornus officinalis
Crataegus crus-galli
Crataegus Phaenopyrum
Crataegus punctata
Crataegus × Lavallei
Diospyros virginiana
Fagus grandifolia
Fraxinus excelsior
Fraxinus pennsylvanica
Gleditsia triacanthos
Halesia carolina
Halesia monticola
Hibiscus syriacus
Ilex opaca
Juglans cinerea
Juglans nigra
Juniperus chinensis
Koelreuteria paniculata
Liquidambar styraciflua
Liriodendron Tulipifera
Maackia amurense
Magnolia acuminata
Magnolia grandiflora
Magnolia Kobus
Magnolia stellata
Magnolia virginiana
Magnolia × Loebneri
Magnolia × Soulangiana
Malus baccata
Malus floribunda
Malus hupehensis
Malus ioensis
Malus sieboldii zumi
Malus tschonoskii
Metasequoia glyptostroboides
Morus species
Nyssa sylvatica
Ostrya virginiana
Oxydendrum arboreum
Pinus Bungeana
Pinus flexilis
Pinus nigra
Pinus ponderosa
Pinus rigida
Pinus sylvestris
Pinus virginiana
Platanus occidentalis
Populus deltoides
Populus spp
Prunus Padus
Prunus Sargentii
Prunus serotina
Prunus serrulata
Prunus virginiana
Prunus yedoensis
Pseudotsuga Menziesii
Ptelea trifoliata
Pyrus betulifolia
Pyrus Fauriei
Quercus alba
Quercus coccinea
Quercus lyrata
Quercus marilandica
Quercus Muehlenbergii
Quercus nigra
Quercus phellos
Quercus prinus
Quercus robur
Quercus stellata
Quercus velutina
Rhus typhina
Robinia Pseudoacacia
Robinia × ambigua
Salix babylonica
Salix nigra
Sassafras albidum
Sophora japonica
Sorbus alnifolia
Stewartia Pseudocamellia
Styrax japonicus
Taxodium distichum
Tilia cordata
Ulmus carpinifolia
Ulmus japonica
Viburnum lentago
Viburnum prunifolium
Viburnum rufidulum
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- APPENDIX 1. AN ABBREVIATED SURVEY INSTRUMENT SHOWING THE FIRST FIVE ENTRIES OF THE ORIGINAL LIST THAT CONTAINED MORE THAN 200 SPECIES. THE HEADER AND THE FIRST TWO COLUMNS WERE FILLED OUT BY RESPONDENTS. THE REMAINING FOUR COLUMNS WERE USED FOR CODING AND TO IDENTIFY PLANTS IN THE SURVEY.
- APPENDIX 2. LIST OF TREES EVALUATED WHERE URBAN FORESTERS’ REQUESTS AND NURSERY PRODUCTION APPROACHED BALANCE (DIFFERENCES WITHIN +/− 70 TREES).
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