Study site.

An exotic plant inventory of the cultural landscape plantings followed by an exotic plant survey of all areas of the estates and an invasive exotic plant assessment of the natural resource areas were conducted in the Summer 2002. At the time, the NPS flora list (Hayes, 1992) for ROVA contained 380 species (native and exotic) known from the cultural landscape and natural areas including herbarium specimens. Because of the volunteer management of the public flower gardens (i.e., no formal recordkeeping from year to year), the thousands of annual and perennial forbs (garden forbs) in these formal gardens were excluded from this study unless they were referenced in the early garden plans (1903 and 1910) and subsequently also found in the flora list, herbarium, or cultural landscape reports (CLRs; years 1981 to 2002). The VAMA Italian garden flora introductions date back to the Bard ownership in 1795, the Hosack and Langdon ownership beginning in 1830, and the Vanderbilt ownership beginning in 1902–03.

Cultural landscape inventory.

CLRs, formal garden plans, forest ecology studies (e.g., Auwaerter, 2009; Kane and Carruth, 1981; O’Donnell et al., 1992; Favretti and Rainey, 1988), and herbarium specimens (Hayes, 1992, 2002; ROVA NHS, 2002) were reviewed 1) to establish the relevance of the species to the “historical preservation time periods” for each estate for specific exotic introductions and 2) to find the location of plantings in the cultivated landscape for these NHS.

Exotic plant survey.

Field investigations of the 800-acre complex occurred from 14 May to 29 July 2002 and as necessary to complete the project through the end of Sept. 2002. Plant species that were targeted in the survey were identified from a review of the historical records, the cultural landscape inventory, and two invasive plant lists available at the time depicting 120 exotic plants as “known or potential invaders” of natural areas. The available invasive exotic plant lists were from the NPS (2002) and the Mid-Atlantic Exotic Plant Pest Council (MAEPPC, 2002). Six introduced native species (Mitchell, 1986; New York Flora Association, 1990) that are key species in the preservation time periods for these estates were also included in the survey and assessment. It is important to note, at the time of this study in 2002, New York State did not have a publicly available invasive plant list. However, since then a ranking system for evaluating non-native plant species for invasiveness in New York has been developed and relevant information included in this report (Jordan et al., 2010).

Survey methodology.

The survey methodology was similar to that used in other invasive plant investigations (e.g., Dewey and Anderson, 2004) and typical weed monitoring/ranking methods used in agricultural crop management in Pennsylvania and New York. Year 2000 U.S. Geological Survey true color aerial photographs (Hayes, 2002) were incorporated into the mapping software (Arc View 3.1; Esri, Redlands, CA). The ROVA sites were divided into 200 × 200-m grids and superimposed on Year 2000 high-resolution color aerial photographs of the six parcels (VAMA, FDR, ELRO, and Top Cottage) further divided into blocks (VAMA—Block A1-H10, etc.), and printed. Site-specific searches were conducted at two scales as single point-in-time observations: 1) the absence or presence of each species for each parcel property and 2) the location within each parcel such as landscape beds, cultivated flower gardens, stone walls, hedgerows, rocky outcrops, riparian areas, open fields, forest edges, dumps, and intermittent streams and ponds. The survey was conducted by extensively walking through each estate until all areas had been visually assessed for the presence of targeted species and detailed field notes recorded (Bravo, 2002). Because of time constraints, recently mowed meadows (formerly crop fields maintained by mowing), inaccessible areas of specific blocks, and the interior flower beds of the FDR, VAMA, and Bellefield public flower gardens that contain thousands of annual and perennial forbs were not inventoried or surveyed. Because more than 400,000 trees were planted on the FDR estate from 1911 to Roosevelt’s death in 1945 (Auwaerter, 2009), some exotic silvicultural species were also excluded. Exotic species identifications were made using taxonomic keys (Fernald, 1989; Peterson and McKenny, 1974; Petrides, 1986; Rhoads and Block, 2000; University of Connecticut, 2002), voucher herbarium specimens, identification fact sheets (U.S. Department of Agriculture, 2002), and as needed verification by taxonomic experts familiar with the flora of the region.

Terms and definitions.

For this study, a clear distinction between cultivated and uncultivated exotic plants was made before conducting the survey and assessment based on historical records, FLORA list, herbarium list, and CLRs. Species’ abundance within ROVA either in the cultivated or uncultivated landscape were defined for the purpose of prioritization in the ROVA invasive species management plan as rare (few individuals only), infrequently occurring (not yet common), frequently occurring, common, and/or widespread throughout and not ranked if no data had been collected. Naturalized is defined as existing, reproducing, and thriving in multiple locations in minimally managed habitats away from cultivation and not associated with any prior cultivated plantings. Lastly, for the purpose of the ROVA invasive species management plan, an invasive plant species is defined as an exotic (and includes “North American native” plant species not native to the ROVA landscape) that has colonized a habitat outside of its historical planting and is reproducing and spreading rapidly or has migrated into ROVA by other means and is displacing native flora in natural resource areas and or is detrimental to the historical preservation of the cultural landscape.

Historical records review.

Review of available CLRs and other historical estate documents indicated that at least 147 (48% of 308 species) of ROVA’s flora were known to be exotic before the start of this study. The last CLRs inventory was reported for FDR by Claeys and Coffin (1995), for VAMA by Glenn (1998), and for ELRO by O’Donnell et al. (1992). The most recent natural resource vascular plant inventories were reported by Rudnicky (1984) and Dutton (1998). The 2002 cultural landscape inventory and natural resource area survey added 16 undocumented exotics to the ROVA flora database bringing the total number of known exotics in the history of ROVA to at least 163.

Cultural landscape and natural resource area survey results.

The CLR's review provided a total of 170 species that were searched for in the cultural landscape. The introduction dates/decade for 102 species (96 exotics and 6 introduced natives) are shown in Table 1. The 102 species surveyed for in the cultural landscape, are best described as ornamentals (65), garden forbs (19), common weeds (8), crops (5), groundcovers (3), and aquatics (2). In all, 93% of the species listed in Table 1 were found in the cultural landscape survey. Although the CLRs provided information on another 68 species known to be present in ROVA at one point in time, they were not listed as invasive plants of concern on available (2002) invasive plant lists and as a means of targeting invasive species of most concern and relevancy to the NPS needs, they were excluded from the natural area assessment. Because of page constraints, 43 species listed on the available exotic plant lists that were surveyed for and not found described as aquatics (7), grasses (6), herbaceous plants (15), shrubs (3), trees (10), and woody/semi-woody vines (2) and the results for the 68 excluded species (surveyed for but not assessed) described as common weeds (38), crops (15), garden forbs (10), and ornamentals (5) are not included in this publication but are available upon request from the lead author as Appendix 1 and 2, respectively.

Table 1.

Year 2002 inventory and survey results for 102 Roosevelt-Vanderbilt National Historic Sites, Hyde Park, NY, introduced plants: 96 exotics and 6 introduced natives and their intended historical purpose and period of introduction.

View Table

Relevant to the estates’ interpretive period timelines, at least 65 species shown in Table 1 have one or more specimens that were introduced (as plantings or referenced as weeds) during the preservation time periods (1900–62) and even some dating to 1799. In fact, there are several trees, shrubs, and woody vines at ROVA at least 90 years of age. Based on the stem girth and “mature” appearance of some of the larger specimens of chinese trumpetvine (Campsis grandiflora), oriental bittersweet (Celastrus orbiculatus), wintercreeper (Euonymus fortunei), english ivy (Hedera helix), ‘Halleana’ japanese honeysuckle [Lonicera japonica (a 3-inch- diameter vine was found at the VAMA estate)], virginia creeper (Parthenocissus quinquefolia), and ‘Veitchii’ boston ivy (Parthenocissus tricuspidata), it is possible some could be the same plantings that James L. Greenleaf, the original architect of the VAMA Italian gardens, specified in the 1903 “Plan No. 63: Diagrams of Plantings for East Half of Gardens” or that Thomas Meechan and Sons suggested in the “1910 Garden Plan prepared for F.W. Vanderbilt Esq., Hyde Park, NY” (Favretti and Rainey, 1988). In fact, of all the exotic species mentioned in the 1903 plan and 1910 plan, only three exotic clematis (Clematis sp.) and chinese pear (Pyrus pyrifolia) were not documented as having been actually planted and were also not found in cultivation in 2002.

The most frequent landscape shrubs honeysuckle, mock orange, and burning bush found in the ROVA cultural landscapes have over the years included plantings of several different species and cultivars. There are at least three cultivars of the introduced orange-flowered trumpetvine (Campsis radicans) at ROVA—one scarlet or deep-red scraggly bush (perhaps ‘Atropurpurea’ or Crimson Trumpet’), the yellow ‘Flava’, and the introduced native orange-flowered vine. There are also at least two distinct cultivars of chocolate vine (Akebia quinata) at ROVA—one white and two purple flowering vines. Unfortunately, the available records used to conduct this study are not detailed enough to evaluate any invasive differences at the cultivar level for all species.

Invasive plant assessment findings.

Of the 102 (96 exotics and 6 introduced natives) introduced plant species, eight [three clematis species, chinese pear, bridalwreath spiraea (Spiraea prunifolia), thunberg’s meadowsweet (Spiraea thunbergii), ‘Regal’ bukhara fleeceflower (Polygonum baldschuanicum), and carolina fanwort (Cabomba caroliniana)] are not currently propagated and were not found in the landscape survey. The bukhara fleeceflower was noted by Claeys and Coffin (1995) to be at least 50 years old in 1981 before its removal from ELRO. Vanhouttei spiraea (Spiraea ×vanhouttei) is in cultivation at ROVA, but because of the presence of other similar native spiraeas in the natural resource areas, it was not assessed. All 90 species listed in Table 2 were assessed for the ROVA NHS invasive species management plan and are categorized in the assessment as “cultivated not escaped,” “cultivated and escaped,” or “not known from cultivation and found naturalized.”

Table 2.

Year 2002 invasiveness assessment for 90 introduced plants currently found at the Roosevelt-Vanderbilt National Historic Sites, Hyde Park, NY: 84 exotics and six introduced native to New York State species and their abundance and invasive listing/ranking in available invasive plant lists.

View Table

Cultivated not escaped.

Thirty-six assessed species cultivated at ROVA (40%), including one introduced native were classified as not invasive within ROVA (Table 2). They are best described as introduced groundcovers (2), introduced garden forbs (1), and the rest [33 (92%)] were introduced as ornamentals. Ten exotic species in this category (28%) were considered invasive or potentially invasive in the 2002 MAEPPC and NPS listings, and 17 exotic species in this category (47%) are categorized as invasive in the 2010 New York rankings (Jordan et al., 2010). The vast majority of these exotics are rare or infrequently found in the cultural landscape and for this reason a few ambiguous detections were classified as not invasive now. For example, discarded clippings of chocolate vine were discovered in the compost dump at VAMA—there are only two old growth vines in the ROVA gardens and a 1991 restoration planting of this species elsewhere in ROVA. Other rarities such as common lilac (Syringa ×vulgaris), privet (Ligustrum sp.), japanese spiraea, and the few locations of flower beds containing crown vetch (Securigera varia) were in the few instances of a detected escape, best described as abandoned plantings or discarded clippings and were not representative of the other cultural landscape plantings elsewhere in ROVA for the same species. However, the survey did reveal a lost planting (LP) of a five-leaf aralia (Eleutherococcus sieboldianus) on Bard Rock. The population was comprised of two to three primary shrubs surrounded by secondary shoots and sprouts numerous enough to form a dense thicket 10 ft wide by 20 ft long. The survey also revealed two juvenile shrubs of another five-leaf aralia planting sprouting adjacent to their regal looking mother plant at the FDR mansion. These shrubs demonstrated the same tendency for their canes to root as was observed for this species in the abandoned hedge on Bard Rock, a feature that was not observed in an old growth aralia bush at the ELRO estate. In 2002, very little information was available to determine if this species has invasive tendencies.

Known from cultivation and escaped.

Forty species are present in the cultivated landscape of ROVA (44%), and escapes of the same species were found in uncultivated areas or beyond the intended area of cultivation (Table 2). They are best described as introduced for wildlife (1), groundcover (1), crops (4), garden forbs (14), and the rest [20 (50%)] as ornamentals. In this category, 17 species (43%) were considered invasive or potentially invasive in the 2002 listings and 21 (53%) are ranked in the 2010 New York listing. Tree-of-heaven (Ailanthus altissima), the introduced native orange-flowered trumpetvine, oriental bittersweet, honeylocust (Gleditsia triacanthos), black locust (Robinia pseudoacacia), and the introduced native virginia creeper are widespread (Table 2) in the natural resource areas with introductions dating from 1900 to 1910 (Table 1). Burning bush, japanese barberry, morrow’s honeysuckle, tatarian honeysuckle, sweet mock orange (Philadelphus coronarius), multiflora rose, and wine berry (Rubus phoenicolasius) are infrequent to common invaders (depending on estate) of the ROVA natural resource areas (Table 2) with introductions dating from 1940 to 1945 (Table 1). While most are clearly escapes from cultivation and rampant (japanese barberry), quite a few old-growth shrubs can be classified as LPs such as the single, impressive, 6-ft-tall burning bush found at Bard Rock and another old growth shrub under the arched-bridge over Crum Elbow creek.

Not known from cultivation and found naturalized.

Fourteen exotic species (16%) were not associated with past or present cultivation in the landscape or formal gardens (Table 2) and based on location are assumed to have migrated into the parcels from adjoining properties, the railroad, the Hudson River, or via adjacent roadways. These species are best described as common weeds (8), garden forbs (3), ornamentals (2), and aquatic (1). Common buckthorn (Rhamnus cathartica) and garlic mustard (Alliaria petiolata) are widespread in the natural resource areas and it would be difficult to eradicate these two invaders. The time line of introduction for louise’s swallowwort (Cynanchum louiseae) and japanese knotweed (Polygonum cuspidatum) is documented in the ROVA flora and are considered recent invaders. There were no CLRs or other historical documentation to suggest that common buckthorn was ever planted in the cultural landscape. Also, it is not possible to determine if the garden forbs in this category were purposefully introduced at ROVA as plantings or were considered common weeds at the time referenced. Nine species in this category (NCN) were included on the regional exotic invasive plant lists and 12 species were included in the 2010 NY ranking. It is important to note that in our study, 71% of the species excluded from the natural resource area invasive assessment (Appendix 2) could also be classified as common weeds or garden forbs but were for unknown reasons not listed as exotic plants of concern on the NPS and MAEEPC invasive plant lists. An invasive assessment of these species within ROVA was not determined in our 2002 study.