VARIETY TRIALS Evaluation of 14 Butterfl y Bush Taxa Grown in Western and Southern Florida: II. Seed Production and Germination
Sandra B. Wilson1, 3, Mack Thetford2, Laurie K. Mecca1, Josiah S. Raymer2, and Judith A. Gersony1
ADDITIONAL INDEX WORDS. exotic plants, invasive, ornamentals, but- terfl y bush, Buddleja davidii, Buddleja japonica, Buddleja lindleyana, Buddleja ×weyeriana
SUMMARY. Because of its weedy nature, extensive use in the landscape, numer- ous cultivars, and history as an inva- sive plant in other countries, butterfl y bush (Buddleja) was an appropriate candidate to evaluate for seed pro- duction and germination in Florida. Seed production was quantifi ed for 14 butterfl y bush taxa planted in western Florida (Milton) and central southern Florida (Fort Pierce). Each of the 14 taxa evaluated produced seed. In Fort Pierce, japanese butterfl y bush (B. japonica) had the greatest capsule weight and ‘Gloster’ butterfl y bush (B. lindleyana) had the second greatest capsule weight as compared to other taxa. In Milton, ‘Gloster’ had the greatest capsule weight and japanese butterfl y bush and ‘Nanho Alba’ butterfl y bush (B. davidii var.
This project was funded by the Florida Department of Environmental Protection and the University of Florida–IFAS Invasive Plant Working Group. Authors gratefully thank Patricia Frey for technical support. Florida Agricultural Experiment Station journal series R-10029. 1University of Florida, Institute of Food and Agricultural Sciences, Department of Environmental Horticulture, Indian River Research and Education Center, Fort Pierce, FL 34945. 2University of Florida, Institute of Food and Agricultural Sciences, Department of Environmental Horticulture, West Florida Research and Education Center, Milton, FL 32583. 3To whom reprint requests should be addressed; e-mail: [email protected]fl .edu
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Oct2004HT.indb 612 9/15/04 12:32:07 PM nanhoensis) had the second greatest functionality, it is not appropriate to is becoming increasingly problematic capsule weights as compared to other label a wild type species as invasive (Staples et al., 2000). Having evaluated taxa. The shape and number of seed without evaluation of cultivars. Wilson 50 butterfl y bush taxa for seed produc- capsules per infructescence varied and Mecca (2003) evaluated eight tion and germination at Longwood with cultivar. Seeds were cleaned and cultivars and the wild type form of Gardens (Kennett Square, Pa.), Anísko germinated in germination boxes with and without light at 20/10, 25/15, mexican petunia (Ruellia tweediana), and Im (2001) recommended nursery 30/20 and 35/25 °C (68.0/50.0, a FLEPPC Category I invasive, and professionals to consider species other 77.0/59.0, 86.0/68.0 and 95.0/77.0 found that seed production, germi- than B. davidii. In Florida, there are no °F). Regardless of temperature or nation, and relative growth rate were vouchered specimens that document cultivar, light was required for germi- highly variable among cultivars. the escape of B. davidii into natural nation. At each temperature, ‘Nanho While it is important to evaluate areas (Wunderlin and Hansen, 2003), Blue’ butterfl y bush (B. davidii var. species that are considered invasive in although it is commonly utilized in nanhoensis) and ‘Moonlight’ butterfl y a given state, it is also important to landscapes of the northern and central bush (B. ×weyeriana) had highest ger- evaluate species that show potential part of the state. A related species, mination rates (63-74%) as compared to become invasive. Williamson and lindley’s butterfl y bush (B. lindleyana) to other taxa. Fitter (1996) suggest that the prob- has escaped cultivation in two counties ability of an established or naturalized in Florida (Wunderlin and Hansen, species becoming a pest is one in ten. 2003) as well as eight other states lorida is the second largest pro- In a survey of 235 invasive and 114 (USDA, 2003). The current study ducer of ornamental plants in non-invasive, woody non-indigenous was conducted to determine how 14 Fthe U.S. with estimated $9.908 species in North America, Reichard and butterfl y bush taxa perform in western billion total industry sales during 2000 Hamilton (1997) found that 54% of the and southern Florida with relation to (Hodges and Haydu, 2002). While successful invaders were also invasive seed production, seed germination, most intentionally introduced species in other places. History of prior inva- and seed viability. remain in their cultivated settings, some sive habit in combination with other escape cultivation and invade natural invasive traits can be used as warning Materials and methods areas. An invasive plant is defi ned as signals for the threat of potential invad- PLANT MATERIAL AND SITE CONDI- a non-indigenous species that has ers. Some of the similar properties that TIONS. Selection of butterfl y bush taxa the ability to establish self-sustaining, constitute a great landscape plant (i.e., (Table 1) was based on availability, expanding populations and may cause long fl owering period, adaptability to popularity, and performance in the economic and/or environmental harm a range of environmental conditions, landscape. Specifi c botanical descrip- (National Invasive Species Council, ease of propagation, and high vigor) tions and experimental conditions 2001; Vitousek et al., 1995). Of the often predispose it as a potentially were previously reported (Wilson 124 plant species listed as invasive by invasive plant in certain geographical et al., 2004). Briefl y, each cultivar the Florida Exotic Pest Plant Council locations. was clonally propagated, transferred (FLEPPC), 67% were introduced as Butterfl y bush is a widely culti- to 3.8-L (1 gal) pots, and fertilized ornamentals (FLEPPC, 2003). The vated, extremely popular, fl owering with 15N–3.9P–10K Osmocote Plus Tampa Bay Wholesale Growers, Florida shrub with attractive foliage and a range (Scotts Co., Marysville, Ohio) prior Nurserymen and Growers Association, of fl ower colors. Wilson et al. (2004) to planting. The experiment was con- and American Nursery and Landscape assessed landscape performance of 14 ducted at Fort Pierce (USDA Zone 9B) Association Boards of Directors were butterfl y bush taxa planted in western and Milton (USDA Zone 8B) where among the fi rst in the nation to adopt and southern Florida and found visual nine uniform plants of each cultivar voluntary codes of conduct (invasive quality and fl owering to vary by month, were planted (4 June 2002) 2.4 m (8 plant best management practices) for cultivar and location. Several cultivars ft) on center on raised beds covered the nursery industry (Baskin, 2002; maintained high visual quality and fl ow- with polyethylene mulch. Plants were Missouri Botanical Garden, 2001). The ering throughout the study. However, watered by seep (Fort Pierce) or drip codes of conduct involve adoption of before recommending specifi c cultivars (Milton) irrigation as needed. risk assessment methods that consider for the Florida landscape or before DATA COLLECTION. Plants were plant characteristics and prior obser- selecting specifi c cultivars for breeding harvested after 25 weeks by severing the vations or experience with the plant programs, additional studies are war- primary shoots at crown level (base of elsewhere in the world. This requires ranted since the species Buddleja davi- the soil). Infructescences were isolated nursery professionals to work with dii has escaped from gardens in other from the shoots. Seed capsules were regional experts to determine which parts of the world and is considered separated from panicle infl orescences species in a given region are either a serious weed in New Zealand (Kay and weighed. Capsule to fl ower ra- currently invasive or may become in- and Smale, 1990), Australia (Csurhes tios were calculated by dividing total vasive. Prolifi c seed production, short and Edwards, 1998) and Great Britain capsule weight by total fl ower weight. juvenile periods, and aggressive growth (Crawley, 1987). In the U.S., it has To estimate total seed production per rates are several of a suite of traits that escaped cultivation in 19 states and plant, 10 representative capsules of each invasive plants characteristically may Puerto Rico [U.S. Department of cultivar were selected, from which seeds share (Reichard, 1997; Rejmánek and Agriculture (USDA), 2003) and can were isolated and counted. Richardson, 1996). Still, since many be found commonly along roadsides, SEED GERMINATION AND VI- ornamental species are hybridized and streamsides and other disturbed areas of ABILITY. Germination studies were selected for an array of color, form and its growing range. In Hawaii, B. davidii conducted on seed collected from 14
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Table 1. Fruit and seed morphology and seed quantity of 14 butterfl y bush taxa evaluated after 25 weeks in western Florida (Milton) and southern Florida (Fort Pierce). Avg no. Avg approx seeds per no. of seeds Common Fruit and seed capsuley per plant name Species Cultivar morphologyz (n = 10) (1000x)x Pink delight Buddleja Pink Delight Seed capsules elliptical, elongated with 18.4 144–555 butterfl y bush davidii pointed ends; light to medium brown in color; 5.5 mm long × 1.4 mm wide. Seeds rounded inside winged sheath, very fi ne. White profusion B. davidii White Profusion Seed capsules slender with pointed ends; 51.5 282–1094 butterfl y bush reddish medium brown in color; 8.4 mm long × 1.3 mm wide. Seeds rounded inside winged sheath, fi ne. Black knight B. davidii Black Knight Seed capsules slender with pointed ends; dark 41.6 281–973 butterfl y bush brown in color; 5.6 mm long × 1.2 mm wide. Seeds rounded inside winged sheath, very fi ne. Nanho white B. davidii var. Nanho Alba Seed capsules slender with pointed ends; 39.5 236–2116 butterfl y bush nanhoensis brown in color; 8.0 mm long × 1.1 mm wide. Seeds rounded inside winged sheath, fi ne. Nanho blue B. davidii var. Nanho Blue Seed capsules slender with pointed ends; medium 81.7 236–1337 butterfl y bush nanhoensis brown in color; 6.1 mm long × 1.2 mm wide. Seeds rounded inside winged sheath, very fi ne. Nanho purple B. davidii var. Nanho Purple Seed capsules elliptical, elongated with 65.1 1096– 2821 butterfl y bush nanhoensis pointed ends; brown to dark brown in color; 5.1 mm long × 1.1 mm wide. Seeds rounded inside winged sheath, very fi ne. Japanese B. japonica Seed capsules rounded, slightly oblong; greenish 140.3 877–1351 butterfl y bush brown in color; 5.1 mm long × 3.8 mm wide. Seeds un-winged, shapes varied and irregular. Lindley’s B. lindleyana Seed capsules oblong with rounded ends; 94.1 319–581 butterfl y bush greenish brown in color; 5.63 mm long × 2.50 mm wide. Seeds un-winged, shapes varied and irregular. Gloster B. lindleyana Gloster Seed capsules rounded, slightly oblong; 125.5 639–2358 butterfl y bush greenish brown in color; 5.2 mm long × 3.0 mm wide. Seeds un-winged, shapes varied and irregular. Honeycomb B. ×weyeriana Honeycomb Seed capsules rounded to oblong; grouped 2.2 0.81–1.10 butterfl y bush in clusters; grayish brown to light brown in color; 4.1 mm long × 2.8 mm wide. Seeds un-winged, light brown to medium brown, shapes varied with many being narrow and bent, fi ne. Moonlight B. ×weyeriana Moonlight Seed capsules rounded, slightly oblong; 18.1 28– 415 butterfl y bush grouped in clusters; grayish green in color; 3.3 mm long × 2.1 mm wide. Seeds un-winged, shapes varied and irregular. Sungold B. ×weyeriana Sungold Seed capsules oblong with rounded ends; 0.9 0.28–13 butterfl y bush grouped in clusters; grayish to medium brown in color; 2.8 mm long × 1.9 mm wide. Seeds un-winged, brown to dark brown, shapes varied, fi ne. Violet eyes B. ×weyeriana Violet Eyes Seed capsules rounded, slightly oblong; 18.9 95–197 butterfl y bush x B. lindleyana grouped in clusters; greenish brown in color; 3.8 mm long × 2.4 mm wide. Seeds un-winged, shapes varied and irregular. Dartmoor B. davidii Dartmoor Seed capsules elliptical, elongated with pointed 43.0 73–711 butterfl y bush x B. davidii ends; medium brown in color; 5.9 mm long × 1.7 var. nanhoensis mm wide. Seeds rounded inside winged sheath, fi ne. z25.4 mm = 1 inch. yCapsules were collected from open-pollinated plants grown in Fort Pierce conditions. xLower and higher ranges of seed count are representative of plants grown in southern and western Florida, respectively.
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OOct2004HT.indbct2004HT.indb 661414 99/15/04/15/04 112:32:082:32:08 PPMM Buddleja taxa grown for 25 weeks in was a randomized complete block with butterfl y bush, although listed as a Fort Pierce, Fla. Seed were collected 14 cultivars and nine single-plant rep- separate species, is minimally different from plants at maturity and allowed lications. Data were collected on each from lindley’s butterfl y bush (Dirr, to dehisce at room temperature [22 plant sample, subjected to analyses of 1998) and sometimes listed as Buddleja to 25 °C (71.6 to 77.0 °F)] in paper variance (ANOVAs), and signifi cant lindleyana var. hemsleyana. It appears bags for 1–2 weeks. Seeds with visible means separated by least signifi cant that seed production varies greatly indication of pathogen or insect dam- difference (LSD) at 0.05. with cultivars of Buddleja lindleyana, age were discarded. In accordance with A split block experimental design since Anisko and Im (2001) reported the Association of Offi cial Seed Analysts was used with temperature as the main ‘Miss Vice’ butterfl y bush (Buddleja (AOSA, 2003), individual treatments block and taxa as the split-plot. Each lindleyana) to not produce any seed. for all germination experiments con- treatment consisted of 50 seeds per ger- Reduced or lack of seed production sisted of four replications of 50 seeds mination box and was replicated four is sometimes characteristic of plants in 10.9 × 10.9-cm (4.29 inches) trans- times. Data were subjected to ANOVA having aggressive vegetative growth or parent polystyrene germination boxes within temperatures. Taxa means were suckering habit (S.B. Wilson, personal (Hoffman Manufacturing, Albany, separated by LSD at 0.05 level. observation). Regardless, the sucker- Ore.) containing two sheets of germi- ing habit of lindley’s butterfl y bush nation paper (Hoffman Manufactur- Results and discussion and japanese butterfl y bush coupled ing) moistened with 15 mL (0.5 fl oz) SEED PRODUCTION. Each of the with the un-winged seed structure nanopure water. Germination boxes 14 taxa evaluated produced seed in may suggest short-distance dispersal, were placed in temperature and light Fort Pierce and Milton (Tables 1 and particularly if seed viability is low. controlled growth chambers equipped 2). In both locations, earliest fruiting While capsule weight is affected by with cool-white fl uorescent lamps was observed for ‘Nanho Blue’ [36 d the capsule wall thickness in addition (Conviron, CMP 4030, Controlled (Fort Pierce) or 12 d (Milton)] after to seed number, capsule production Environments, Winnipeg, Canada). planting of 8-week-old rooted liners for each cultivar at each location is Germination boxes were placed in light (data not shown). Other cultivars such interesting to note. In Fort Pierce, (12-h photoperiod) or darkness (no as ‘Sungold’ (Buddleja x weyeriana) did japanese butterfl y bush had the great- photoperiod) at 20/10, 25/15, 30/20 not fruit until day 79 (Fort Pierce) or est capsule weight and ‘Gloster’ had and 35/25 °C. The 12-h photoperiod day 58 (Milton) (data not shown). the second greatest capsule weight was maintained in each chamber with Average number of seeds per as compared to other taxa (Table 2). an average photosynthetic photon capsule varied widely among taxa with In Milton, ‘Gloster’ had the greatest fl ux of 84 µmol m-2 s-1 at shelf level. japanese butterfl y bush having the capsule weight, and japanese butterfl y The diurnal treatment with light was largest number of seeds per capsule bush and ‘Nanho Alba’ (Buddleja da- administered by providing 12 h light and ‘Sungold’ having the least number vidii var. nanhoensis) had the second at 20, 25, 30 or 35 °C followed by of seeds per capsule (Table 1). Fruit greatest capsule weights as compared 12 h of dark at 10, 15, 20, or 25 °C, capsules of lindley’s butterfl y bush or to other taxa. In both locations, ‘Dart- respectively. Dark treatments were japanese butterfl y bush contained many moor’ (Buddleja davidii x Buddleja administered by wrapping germina- small seed stacked in layers (94 to 140 davidii var. nanhoensis), ‘Honeycomb’ tion boxes in two layers of heavy duty average seeds per capsule). Japanese (Buddleja ×weyeriana) and ‘Sungold’ aluminum foil. These dishes remained unopened until the fi nal day of the experiment. Germination of seed ex- Table 2. Average capsule weight and capsule : fl ower ratios per plant of posed to light was monitored daily for fourteen butterfl y bush taxa planted in Fort Pierce (southern Florida) and a period of 28 d. A seed was considered Milton (western Florida) for 25 weeks. germinated when radicle emergence Capsule wt (g)z Capsule : fl ower ratio was ≥2.0 mm (0.08 inch). At the end Taxa Fort Pierce Milton Fort Pierce Milton of the germination period, fi nal ger- mination percentage (FGP) and T50 Black Knight 16.9 58.5 0.40 0.64 (days to 50% of FGP) were determined Pink Delight 15.7 60.3 0.19 0.55 per germination box. White Profusion 16.4 63.7 0.12 0.25 In accordance with the AOSA Nanho Alba 16.7 150.0 0.10 0.74 (2000), seed viability tests were repli- Nanho Blue 7.8 44.2 0.16 0.44 cated twice on 100 seeds per cultivar. Nanho Purple 30.3 78.0 0.30 0.49 Seeds were stained for 48 h at 40 ºC Dartmoor 4.4 43.0 0.03 0.14 (104.0 ºF) in 1% tetrazolium (2, 3, Lindley’s butterfl y bush 30.5 55.6 0.96 0.53 5-triphenyl chloride) solution with Gloster 55.0 202.9 0.68 0.82 positive staining patterns confi rming Japanese butterfl y bush 95.6 147.3 4.85 0.60 seed viability (Mid-West Seed Service, Violet Eyes 24.0 50.1 0.32 0.29 Brookings, S.D.). Honeycomb 1.5 1.1 0.02 0.01 EXPERIMENTAL DESIGN AND STA- Moonlight 5.5 80.3 0.11 0.44 TISTICAL ANALYSIS. The fi eld experi- Sungold 0.4 18.8 0.01 0.13 ments were conducted at Milton and LSD (0.05)y 14.8 42.0 0.57 0.26 Fort Pierce, Fla. The experimental z1.0 g = 0.035 oz. design from which seeds were collected yMeans separated by least signifi cant difference test at 0.05.
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on average had a capsule:fl ower dry (Wilson et al., 2004) with capsules with temperature and taxa (Table 3). weight ratio that was 56% to 98% containing 1.7 to 2.1 times greater At 20/10 °C, T50 values ranged from lower than that of other cultivars. The the amount of seeds as ‘Nanho Alba’ 13.5 d (‘Violet Eyes’ and ‘Moonlight’) shape and number of seed capsules per or ‘Nanho Purple’ (Table 1). to 22.5 d (‘Nanho Purple’), whereas at infructescence also varied with cultivar GERMINATION AND VIABILITY. 35/25 ºC, T50 values were lower rang- (Table 1). Seeds of all Buddleja davidii, All taxa produced suffi cient seed for a ing from 6 d (japanese butterfl y bush) Buddleja davidii var. nanhoensis, and complete germination study with the to 16 d (‘Honeycomb’). Germination Buddleja davidii x Buddleja davidii exception of ‘Sungold’. Of the remain- rate can be a useful measure of the var. nanhoensis cultivars were contained ing 13 taxa that could be evaluated, speed or velocity of germination since within a winged sheath, whereas seeds all produced a percentage of viable germination patterns can be different of Buddleja lindleyana, Buddleja xw- seed with germination varying among even if fi nal germination percentages eyeriana, and Buddleja x weyeriana x temperature treatments (Table 3). are almost identical (Hartmann et al., Buddleja lindleyana were not winged. Regardless of cultivar or temperature, 2002). The winged adaptation may facilitate seeds had little or no germination (0 Results indicate that 50% or more seed dispersal by wind (Staples et al., to 5%) in the dark (data not shown). of seeds from cultivars of butterfl y bush 2000). At 20/10 °C ‘Nanho Blue’ had the such as ‘Nanho Blue’ and ‘Moonlight’ Butterfl y bush species tend to re- greatest germination, and at 25/15 °C have the capacity to germinate readily tain their seed capsules after dehiscence ‘Moonlight’ had the greatest germina- over a broad range of temperatures. making it possible to estimate seed tion, as compared to other cultivars. Several weed species have been shown production at the end of a growing At 30/20 °C, ‘Nanho Blue’, japanese to germinate over a wide range of season. When computing the average butterfl y bush and ‘Moonlight’ had temperatures (Balyan and Bhan, 1986; number of seeds per capsule with the similarly high germination (53% to Susko et al., 1999). Still, germination average number of capsules per plant, 66%). ‘Nanho Blue’ and ‘Moonlight’ and viability was comparatively low as ‘Nanho Purple’ (Buddleja davidii also had highest germination (53% to to that found in weed species. Some var. nanhoensis) had the potential to 63%) at 35/25 ºC. It is interesting seed decay and subsequent fungal produce over 1 million seeds in Fort to note that although ‘Nanho Alba’ growth was observed for each cultivar Pierce (Table 1). In Milton, ‘White had less than 3% germination of seeds but was pronounced for ‘White Pro- Profusion’ (Buddleja davidii), ‘Nanho collected in Fort Pierce, up to 35% fusion’. Ungerminated, turgid seeds Blue’, and lindley’s butterfl y bush had germination has been observed for without fungal growth would indicate the potential to produce over 1 mil- seeds collected from plants in Milton dormancy. Dormancy is a property of lion seeds and ‘Nanho Alba’, ‘Nanho and germinated under similar condi- many weed seeds that enable them Purple’ and ‘Gloster’ had the potential tions, suggesting that this cultivar can to survive harsh conditions and to to produce over 2 million seeds in a produce seeds with greater viability germinate at a later time or in another single growing season (Table 1). This under different conditions. location when conditions become information is useful, since length of The least number of mean days more favorable (Baskin and Baskin, fl owering period does not necessarily to achieve 50% germination varied 2001). Butterfl y bush is reported to indicate high seed production. Per- rins et al. (1992) reported that the length of the fl owering period was Table 3. Final germination percent (FGP) and number of days to 50% of fi nal germination (T50) of seed collected from 14 butterfl y bush taxa grown in Fort greater in weedy species as compared Pierce, Fla. Seeds were germinated with light (12-h photoperiod) in germination to non-weedy species. Long fl owering boxes placed in growth chambers set at 20/10, 25/15, 30/20 and 35/25 °C periods may allow greater accessibility (68.0/50.0, 77.0/59.0, 86.0/68.0 and 95.0/77.0 °F) for 28 d. to pollinators and a greater chance of seed set (Reichard, 1997). This was not Germination (%) T50 (d) consistent with all butterfl y bush taxa Taxa 20/10 25/15 30/20 35/25 20/10 25/15 30/20 35/25 evaluated since ‘Dartmoor’ continually Black Knight 28.6 17.5 22.5 14.7 18.8 12.5 9.5 11.0 fl owered (50% to 75% canopy coverage) Pink Delight 24.8 24.8 32.3 23.9 20.5 12.0 10.0 9.5 throughout the study at both locations White Profusion 12.1 13.0 17.1 12.1 15.5 8.5 7.8 9.0 (Wilson et al., 2004), yet produced Nanho Alba 0.8 2.9 1.0 1.9 19.0 12.5 20.0 14.0 relatively few seeds (Tables 1, 2). In Nanho Blue 71.2 63.0 65.5 62.7 14.8 8.8 8.0 8.8 Milton, the consistently high fl ower- Nanho Purple 18.3 21.5 29.4 16.7 22.5 17.5 13.3 15.8 ing (75% or higher canopy coverage) Dartmoor 14.8 16.2 15.4 9.1 20.3 11.8 10.3 10.0 of ‘Nanho Alba’ throughout most of Lindley’s the study (Wilson et al., 2004) was butterfl y bush 18.6 13.6 32.2 28.1 17.0 11.0 7.0 7.3 refl ected in subsequently high seed Gloster 34.7 29.2 27.6 35.0 16.0 11.0 7.8 7.8 production and high capsule : fl ower Japanese ratios (Table 2). It was not always pos- butterfl y bush 42.2 47.5 53.3 40.2 16.3 9.5 5.5 6.0 sible to correlate the amount of seed Violet Eyes 45.5 29.8 43.1 20.5 13.5 9.75 7.5 8.3 produced by different butterfl y bush Honeycomb 11.8 25.6 15.2 12.3 18.3 17.0 13.5 16.0 taxa to the size of the infructescence. Moonlight 51.8 74.1 63.4 52.6 13.5 8.0 7.3 8.0 For example, of the Buddleja davidii z var. nanhoensis cultivars, ‘Nanho Blue’ LSD (0.05) 12.4 8.9 12.9 10.6 2.6 2.0 1.8 3.0 generally had shorter infl orescences zMeans separated by least signifi cant difference test at 0.05.
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OOct2004HT.indbct2004HT.indb 661616 99/15/04/15/04 112:32:092:32:09 PPMM have deep dormancy and may remain may be attributed to the presence of Csurhes, S. and R. Edwards. 1998. Po- in the soil for many years (Paterson, root knot nematodes (Thetford and tential environmental weeds in Australia: 2000) but to our knowledge, studies Kinlock, 2002). Candidate species for preventative control. have not been designed specifi cally The results from these studies Biodiversity Group, Canberra, Australia. to document this. Separate tetrazo- suggest that quantity of seed produc- Dirr. M.A. 1998. Manual of woody land- lium tests generally concurred with tion differs greatly among butterfl y scape plants. Stipes Publ., Champaign, percent germination of viable seed bush taxa and location. Taxa such as Ill. where positive staining values were ‘Dartmoor’ and japanese butterfl y Florida Exotic Pest Plant Council. 2003. similar or slightly higher (3% to 12%); bush had similarly high visual quality List of Florida’s invasive species. 8 Apr. with the exception of ‘Black Knight’ and landscape performance (Wilson 2003.
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Rejmánek, M. and D.M. Richardson. 1996. What attributes make some plant species more invasive? Ecology 77:1655–1661. Staples, G.W., D.R. Herbst, and C.T. Imada. 2000. Survey of invasive or poten- tially invasive cultivated plants in Hawaii. Bishop Museum Press, Honolulu. Susko, D.J., J.P. Mueller, and J.F. Spears. 1999. Infl uence of environmental factors on germination and emergence of Pueraria lobata. Weed Sci. 47:585–588. Thetford, M. and R.A. Kinloch. 2002. Galling response of 50 woody landscape species grown in Meloidogyne incognita- and M. arenaria-infested soils. Proc. Southern Nursery Assn. Res. Conf. 47:258–264. U.S. Department of Agriculture National Resources Conservation Service. 2003. The PLANTS Database, Version 3.5 Natl. Plant Data Ctr., Baton Rouge, La. 10 Oct. 2003.
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