Cogongrass is a highly invasive, perennial grass that is found on all continents, except Antarctica. It continues to spread at an alarming rate in the southeastern United States. Cogongrass has been reported from a wide array of habitats; however, soils from areas where cogongrass grows have never been characterized. Live cogongrass plants, herbarium specimens, and soil samples were collected from 53 cogongrass populations from across the 10 physiographic regions and land use areas in Mississippi. Cogongrass leaf and inflorescence morphology varied among sites, and plants were found in soils varying widely in texture (ranging from 28 to 86% sand, 3 to 48% silt, and 6 to 43% clay), organic matter content (ranging from 0.9 to 5.0%), pH (ranging from 4.4 to 8.0), and nutrient status: 6 to 190 kg ha−1 (15 to 470 lb A−1) of phosphorus (P), 46 to 734 kg ha−1 of potassium (K), 150 to 7,620 kg ha−1 of calcium (Ca), 26 to 1,090 kg ha−1 of magnesium (Mg), 1 to 190 kg ha−1 of zinc (Zn), 145 to 800 kg ha−1 of estimated sulfur (S) based on organic matter, and 57 to 300 kg ha−1 of sodium (Na). These soil parameters were highly variable among cogongrass populations, even within physiographic regions or land use areas, and encompassed much of the soil physiochemical diversity within the state. Soil characteristics were significantly correlated with leaf length (Ca, K, Mg, P, Zn, and percentage of sand and silt), leaf width (Ca, P, Mg, and percentage of sand and silt), the leaf length-to-width ratio (K and P), inflorescence length (Na, P, and pH), inflorescence width (S, organic matter, and pH), and the inflorescence length-to-width ratio (S and organic matter). These data indicate that cogongrass is able to establish, emerge, grow, and reproduce on a wide array of soils in Mississippi. This ability provides cogongrass an advantage over other plant species that are more limited in the soil types that support their growth.

Hybridization between two introduced plant species can influence the invasion capabilities of the exotic taxa, but the role of hybridization will likely differ in different invasions, even of the same species. Until now, studies concerning the ploidy of Japanese knotweed, giant knotweed, and their hybrids have been conducted in Europe or native ranges in Asia. Here, we assess the role of hybridization and ploidy in a U.S. invasion. We use flow cytometry to characterize DNA content in (1) established families in a common garden, (2) seedlings grown from common garden parents, and (3) wild populations. We also measured fertility in the garden and the field and vegetative growth traits in the garden. Although the majority of our parental and hybrid samples had ploidy levels previously documented in Europe (4X and 8X for parental species; 6X for hybrids), we found a wider range of knotweed cytotypes established in our garden (4X, 6X, 7X, 8X, 9X, and 10X) and additionally detected 5X, 11X, 12X, and possibly 14X ploidy levels in progeny from garden seed parents. The unexpected cytotypes were not confined to the greenhouse or common garden, in that all < 11X ploidy levels were also found in field populations in Massachusetts. In several cases, these data contradicted our expectations on the basis of morphological and molecular analysis, suggesting both significant introgression and the introduction of multiple cytotypes from Asia. With one exception (14X), we found all cytotypes were capable of strong vegetative growth, seed set, and the production of viable pollen. Without barriers to sexual reproduction, introgression is expected to progress, creating a progressively more diverse swarm of invasive genotypes.

Natural grasslands are one of the most threatened ecosystems in North America. Conservation efforts are often hampered by exotic plant invasions in existing remnant natural grasslands. Tall fescue [Schedonorus phoenix (Scop.) Holub.] is an introduced cool-season (C3) forage/turf grass which readily invades natural grasslands in Kentucky and neighboring states. Our study objectives were to (1) compare the efficacy and application timing effect of clethodim to that of imazapic to selectively remove tall fescue from natural grasslands and (2) evaluate the response of the nontarget grassland plant community (i.e., native grass and forb canopy cover) following herbicide treatments. Clethodim and imazapic treatments consisted of early (April 4, 2001) and late (April 20, 2001) applications, and these were applied at 0.23 and 0.21 kg ai ha−1, respectively. Both herbicides reduced tall fescue cover (P ≤ 0.05); herbicide application timing had no effect on herbicide efficacy to control tall fescue. Native grass cover was higher (P ≤ 0.05) in all herbicide-treated plots compared to the untreated controls, except for the late clethodim-treated plots. All herbicide treatments increased forb abundance compared to controls. Spring applications of clethodim were equally effective to those of imazapic at controlling tall fescue in natural grasslands. Imazapic released native grasses better than clethodim, whereas clethodim was better at increasing forb abundance. Furthermore, early clethodim treatments had fewer nontarget effects on native C4 grasses compared to late clethodim treatments. Overall, clethodim shows promise as a beneficial management tool for tall fescue control in C4-dominated natural grasslands.

Land managers have long identified a critical need for a practical and effective framework for designing restoration strategies, especially where invasive plants dominate. A holistic, ecologically based, invasive plant management (EBIPM) framework that integrates ecosystem health assessment, knowledge of ecological processes, and adaptive management into a successional management model has recently been proposed. However, well-defined principles that link ecological processes that need to be repaired to tools and strategies available to managers have been slow to emerge, thus greatly limiting the ability of managers to easily apply EBIPM across a range of restoration scenarios. The broad objective of this article is to synthesize current knowledge of the mechanisms and processes that drive plant community succession into ecological principles for EBIPM. Using the core concepts of successional management that identify site availability, species availability, and species performance as three general drivers of plant community change, we detail key principles that link management tools used in EBIPM to the ecological processes predicted to influence the three general causes of succession. Although we acknowledge that identification of principles in ecology has greatly lagged behind other fields and recognize that identification of ecological principles and the conditions in which they hold are still being developed, we demonstrate how current knowledge and future advances can be used to structure a holistic EBIPM framework that can be applied across a range of restoration scenarios.

Brown flatsedge (Cyperus fuscus) is widely distributed in Europe, Asia, the Indian subcontinent, and the Mediterranean region of Northern Africa. It was apparently introduced into North America in the late 1800s and has steadily moved southward and westward. Brown flatsedge is reported new to Arkansas and Mississippi herewith. Field observations from early spring until frost were made between 2003 and 2007 from populations present at three sites: Chicot County, Arkansas, and Pearl River and Washington counties, Mississippi. Under natural field conditions, brown flatsedge plants germinated from late March and early April until frost. Inflorescences were observed in mid-May and seed production continued until frost. In field populations, the average numbers of scales per spikelet, inflorescences per plant, and spikelets per inflorescence were 15, 28, and 33, respectively. Greenhouse experiments were established in 2008 at Stoneville, MS, to determine growth parameters and the reproductive potential of brown flatsedge. In greenhouse experiments, by 10 wk after emergence (WAE), brown flatsedge plants were 30.2 cm tall and 63.9 cm in diameter, and dry weights were 1.4, 1.0, 2.0, 0.5, and 1.9 g for roots, culms, leaves, bracts, and inflorescences, respectively. Brown flatsedge culms and inflorescences appeared 5 WAE, and by 9 WAE all plants were producing seed. Brown flatsedge could pose a threat to natural plant communities and rice agriculture in Arkansas, Louisiana, Mississippi, Missouri, Tennessee, and Texas. Additional research is needed to determine seed longevity and ecological range potential, and to develop inexpensive and effective control methods.

Japanese climbing fern (Lygodium japonicum) is an invasive vine that has been identified as an economic and ecological threat in forest ecosystems of the Southeast. In two separate studies, we examined the use of directed sprays of glyphosate, imazapyr, and metsulfuron-methyl herbicides, alone and in combination, for control of Japanese climbing fern and for impacts to associated vegetation in mixed bottomland hardwood–cypress forests at two first terrace sites of the Apalachicola River in north Florida. Two yr after treatment, various rates of glyphosate alone generally provided greater percent control (84 to 95%) than imazapyr alone (−25 to 86%) or metsulfuron-methyl alone (−5 to 53%). Combinations of 2% glyphosate and imazapyr and/or metsulfuron-methyl resulted in 81 to 97% control at 2 yr after treatment, with no significant differences among the combination treatments or 2% glyphosate alone. Change in percent cover of associated vegetation groups was not influenced by treatment except for one location where graminoid cover increased 1 yr after metsulfuron-methyl treatment but decreased after imazapyr or glyphosate application. Species richness of dominant understory vegetation remained nearly constant at both locations regardless of treatment. These data indicate that glyphosate alone or in combination with imazapyr or metsulfuron-methyl will provide effective, although not complete, control of Japanese climbing fern, and that directed herbicide sprays minimally impact nontarget vegetation.

Focus group methodology in a field demonstration setting was used to obtain qualitative data on the perceptions of family forest owners relating to treatment efficiency and feasibility of herbicide control methods. Interviews took place on sites where various strategic herbicide treatments were implemented for Chinese privet (Ligustrum sinense) control using the active ingredients glyphosate and metsulfuron. Forest owners expressed unease about the possibility for post-treatment privet reestablishment due to reseeding or other factors and opinions surfaced calling for selective chemicals or application methods that would spare non-target species. Furthermore, treatment cost effectiveness with regard to timber value, the possible need for expensive multiple treatments, cost-share incentives, and treatment guarantees from herbicide applicators were participant concerns. Environmental concerns surfaced about possible effects of both herbicide use and the invasion of privet on natural systems and an unexpected result was a strong feeling among the forest owners that focus groups are a powerful demonstration tool.

Parrotfeather is an invasive, aquatic plant in the United States that is native to South America. It has impaired the use of water bodies throughout the United States and is difficult to control, despite using a variety of management techniques. Our objectives were to examine the efficacy of subsurface applications of seven herbicides labeled for aquatic use and to compare those applications to herbicides that can also be applied to emergent foliage. A replicated mesocosm study was conducted in 378-L (100-gal) tanks beginning in August 2007 and repeated during the same period in 2008. The maximum and half-maximum labeled rates of copper chelate, diquat, endothall, fluridone, triclopyr, and carfentrazone-ethyl were applied to the water column in designated mesocosms. The maximum labeled rate for foliar applications of diquat, triclopyr, and 2,4-D were used to compare treatment methods. Six weeks after treatment (WAT), copper, endothall, fluridone, and carfentrazone-ethyl did not achieve 90% control; in fact, control was less than 50% for each herbicide, and therefore, the herbicides were not considered efficacious for controlling parrotfeather. Diquat at all rates and application methods resulted in 70 to 90% biomass reduction. Triclopyr, with both the highest aqueous concentration and foliar application, resulted in an 84 and 86%, respectively, reduction in biomass at 6 WAT. The foliar application of 2,4-D was the only herbicide and application method that resulted in ≥ 90% biomass reduction of parrotfeather. In these studies, regrowth occurred in all tanks regardless of herbicide or treatment method, indicating multiple applications would be necessary to provide longer-term plant control. Future research should identify possible herbicide combinations or timing of applications to maximize treatment efficacy.

Meadow hawkweed is an invasive, perennial forb of upland forest openings, mountain meadows, permanent pastures, and abandoned farmlands in the Pacific Northwest. The objective of this study was to measure the plant community response, following meadow hawkweed control using selective herbicides and a single application of N–P–K fertilizer, across three levels of meadow hawkweed infestation in cleared forestlands that had been converted to pasture in northern Idaho. Clopyralid was applied to meadow hawkweed rosettes at a rate of 0.59l kg ae ha−1 (0.528 lb ac−1), and fertilizer (23–5–5, 1% Fe, 14% S) was broadcast following herbicide applications at two rates, 44 and 88 kg N ha−1. Foliar cover of meadow hawkweed, Idaho fescue, and other perennial grasses was measured in microplots at three levels of initial meadow hawkweed cover; < 25%, 40 to 60%, and > 75%. Clopyralid treatments resulted in excellent meadow hawkweed control 3 mo after treatment (MAT). Clopyralid alone appeared to shift the competitive balance in favor of perennial grasses, which increased 7, 44, and 65% above pretreatment levels in LOW, MED, and HIGH hawkweed cover plots, respectively, across fertilizer treatments. Meadow hawkweed cover remained < 5% in clopyralid plots at 52 MAT. Fertilizer effects were confined to interactions between Idaho fescue and other perennial grasses.

The extent and nature of spread of exotic plant species to and within Alaska by shipment of hay and straw was studied. The amounts of hay and straw imported into Alaska and the amounts and types of seed in imported and locally produced hay and straw was determined We purchased alfalfa hay, wheat straw, ryegrass straw, and timothy hay produced in Washington and Oregon (WA–OR) and locally produced straw and hay. The hay and straw were shaken over screens, and the remaining fines were mixed with sterile potting soil and incubated in the greenhouse. Forty-nine plant species were identified from hay and straw, nine of which are ranked as invasive in Alaska, including downy brome, foxtail barley, hare barley, narrowleaf hawksbeard, and quackgrass—a prohibited weed in Alaska. The number of seeds ranged from 0 to 6,205 seeds kg−1, with an average of 585 seeds kg−1, and the number of species ranged from 0 to 12, with an average of 4.2 species per bale. Crop seed comprised a large proportion of the germinated seeds in ryegrass straw, wheat straw, and timothy/brome hay (98, 78, and 62%, respectively), but was less prevalent (ranging from 0 to 38%) in the other three hay and straw crop types. Hay and straw from Alaska contained more total seeds and species than hay and straw from WA-OR, but the difference was not significant when only weed seed was used in the analysis. Alaska-grown timothy/brome hay contained significantly more total seed than alfalfa hay and wheat straw from WA–OR and Alaska-grown barley straw. The grower or distributor of the hay and straw also influenced the number of seeds and species among some crop types. Results of this study document that large numbers of alien plant species are transported by movements of hay and straw into and within Alaska.

Wild potato contains about 100 species that are native to the Americas from the southwestern United States to central Chile and adjacent Argentina, Uruguay, Paraguay, and southern Brazil. We report the occurrence of naturalized populations of the wild potato Solanum chacoense in seven sites in southern Australia, eastern China, England, New Zealand, the eastern United States, central Peru, and east-central Argentina. Modeling similar climatic niches on the basis of the distribution of S. chacoense from South America shows that observations of naturalized S. chacoense overlap with predicted areas. A literature review reveals that although S. chacoense possesses traits typical of an invasive species, all populations presently appear to be contained near their site of introduction.

Understanding the relative importance of various functional groups in minimizing invasion by medusahead is central to increasing the resistance of native plant communities. The objective of this study was to determine the relative importance of key functional groups within an intact Wyoming big sagebrush–bluebunch wheatgrass community type on minimizing medusahead invasion. Treatments consisted of removal of seven functional groups at each of two sites, one with shrubs and one without shrubs. Removal treatments included (1) everything, (2) shrubs, (3) perennial grasses, (4) taprooted forbs, (5) rhizomatous forbs, (6) annual forbs, and (7) mosses. A control where nothing was removed was also established. Plots were arranged in a randomized complete block with 4 replications (blocks) at each site. Functional groups were removed beginning in the spring of 2004 and maintained monthly throughout each growing season through 2009. Medusahead was seeded at a rate of 2,000 seeds m−2 (186 seeds ft−2) in fall 2005. Removing perennial grasses nearly doubled medusahead density and biomass compared with any other removal treatment. The second highest density and biomass of medusahead occurred from removing rhizomatous forbs (phlox). We found perennial grasses played a relatively more significant role than other species in minimizing invasion by medusahead. We suggest that the most effective basis for establishing medusahead-resistant plant communities is to establish 2 or 3 highly productive grasses that are complementary in niche and that overlap that of the invading species.

Dispersal is a critically important process in the spread of invasive plants. Although knowledge of dispersal will be crucial to preventing the spread of invasive plants, little research has been performed within this context. Many important invasive or agricultural weeds disperse their seeds via tumbling, yet only one previously published paper investigated this dispersal mechanism. Field and wind tunnel experiments were conducted to quantify and model tumbling dispersal. We developed competing models for diffuse knapweed seed dispersal from wind tunnel experiments and compared predictions to data collected from a field site in Colorado. Seeds were retained in plants that had traveled hundreds to as much as 1,039 m (3,408 ft). Although neither model accurately predicted dispersal when compared with independent field data, surprisingly, seed retention with distance was somewhat better described as a linear process than as exponential decay. Wind tunnel trials showed no evidence that the number of seeds deposited per meter depended on plant size. Thus, fecundity might be a key factor determining seed dispersal distances; plants with higher fecundity might disperse seeds over longer distances than those with fewer seeds.

Caucasian Old World bluestem (OWB) has escaped into native rangelands and could have unknown effects on distribution, utilization, growth, and reproduction of native plant and animal species. This trial was established to determine the rate and timing of glyphosate application that will provide the greatest OWB suppression. Treatments included glyphosate applied early at the five-leaf stage of growth with 1.12, 2.24, or 3.36 kg glyphosate ai ha−1 (1, 2, or 3 lb ai ac−1), sequential application with an early glyphosate application of 1.12, 2.24, or 3.36 kg ha−1 followed by a second application 8 wk later of either 1.12 or 2.24 kg ha−1, and a late-only application of 1.12, 2.24, or 3.36 kg ha−1. Sequential glyphosate applications with at least one of the early or late applications being 2.24 kg ha−1 or more reduced OWB frequencies from over 87% to below 30% each year. During a moist year, all sequential application treatments reduced OWB frequency to 12% or less. Frequency of OWB the year after application was directly related (r2 = 0.91) to the total amount of glyphosate applied during dry conditions. Seed heads were absent or nearly absent in all sequential application treatments, with the exception of glyphosate at 1.12 kg ha−1 applied early and late during the dry season. Sequential application of glyphosate that includes one treatment either early or late of 2.24 or 3.36 kg ha−1 appears to be the most effective treatment to reduce established OWB during dry years. During years of adequate moisture, a single late application of 2.24 or 3.36 kg ha−1 or sequential applications with 1.12 kg ha−1 at each application is as adequate as sequential applications with greater rates for reducing OWB frequency and achieving OWB control.

Navua sedge, a member of the Cyperaceae family, is an aggressive weed of pastures in Fiji, Sri Lanka, the Malay Peninsula, Vanuatu, Samoa, the Solomon Islands, and Tahiti and is now a weed of pastures and roadsides in north Queensland, Australia. Primarily restricted to areas with an annual rainfall exceeding 2,500 mm (98.4 in), Navua sedge is capable of forming dense stands, smothering many tropical pasture species. Seventeen herbicides were field tested at three sites in north Queensland, with glyphosate, halosulfuron, hexazinone, imazapic, imazapyr, or MSMA as the most effective for Navua sedge control. Environmental problems, such as persistence in soil, lack of selectivity, and movement off-site, may occur using some herbicides at the predicted 90% lethal concentration (LC90) control level rates. A seasonality trial using halosulfuron (97.5 g ai ha−1 [1.4 oz ac−1]) gave better Navua sedge control (84%) by spraying in March to September than by spraying at other times (50%). In a frequency trial, sequential glyphosate applications (2,160 g ae ha−1) every 2 mo was more effective for continued Navua sedge control (67%) than a single application of glyphosate (36%), although loss of ground cover would occur. In a management trial, single applications of glyphosate (2,160 to 3,570 g ae ha−1) using either a rope wick, ground foliar spraying, or a rotary rope wick gave 59 to 73% control, whereas other treatments (rotary hoe, 3%; slashing, −13%; crushing, −30%) were less effective. In a second management trial, four monthly rotary wick applications were much more effective (98%) than four monthly crushing applications (42%). An effective management plan must include the application of regular herbicide treatments to eliminate Navua sedge seed being added to the soil seed bank. Treatments that result in seed burial, for example, discing, are likely to prolong seed persistence and should be avoided. The sprouting activity of vegetative propagules and root fragmentation also needs to be considered when selecting control options.

Beach vitex is an invasive plant of coastal areas of the southeastern United States from Maryland to Georgia. Many resources have been dedicated to the control of established beach vitex stands. Successful eradication will require knowledge of this plant's ability to reestablish from seed after control efforts. To understand seed-based regenerative potential, studies were conducted to characterize the fruits and seeds, document the existence and size of seed banks, determine stratification requirements for germination, and ascertain seed dormancy mechanisms. Studies of fruit lots from three consecutive years (2003 to 2005) found that the average fruit contained 1.39 seeds, and more than 76% of fruits contained at least one viable seed. A positive correlation existed between seed number and both fruit mass and fruit diameter. A substantial soil seed bank was discovered that contained viable seeds 4 yr after vegetation removal. Stratification was required for seed germination. All stratification treatments induced germination, with highest rates realized when stratification was performed at 10 C for 8 or 12 wk. Germination rates were modestly increased (from 0 to 17%) through mild scarification in the absence of stratification. Results indicate that beach vitex has physical (fruit coat) and physiological (seed) dormancy mechanisms that are capable of delaying germination for multiple seasons, allowing development of a soil seed bank. Beach vitex can reestablish from seed after vegetation removal.

Amur honeysuckle recovery following treatments annually and only in 1-year, during 2002 to 2009, was compared in the forests of Radnor Lake State Natural Area in Nashville, TN. Annual treatment areas had significantly lower mean Amur honeysuckle plant counts than 1-yr treatment areas for both ≤ 1 m (3.3 ft) and > 1 m plant heights and on both sloped and level areas, except for plants ≤ 1 m tall on level areas, which most likely indicated more soil moisture increasing seedling establishment and root sprouting in the first year after treatment. The significant, positive Pearson's product moment correlations for Amur honeysuckle counts of plants ≤ 1 m tall, with arboreal basal area and with canopy species diversity in the level areas of the annual treatment plots, were also most likely evidence for the importance of greater soil moisture during the first year after treatment for greater Amur honeysuckle recovery. For land managers interested in native vegetation restoration, guidance is provided to plan for long-term, invasive plant species treatment and recovery monitoring.

Beach vitex is a salt-tolerant, perennial, invasive shrub that has naturalized in coastal areas of the southeastern United States. Since its introduction in the 1980s, this Pacific Rim native has invaded many fragile beach-dune ecosystems along the Mid-Atlantic, Southern Atlantic, and Gulf of Mexico. Large-scale monocultures of beach vitex supplant native species through rapid vegetative reproduction and seed production. Fruits are capable of water-based dispersal, allowing for potential rapid range expansion in coastal areas. Ecosystem damage resulting from exclusion of native plant species by beach vitex and fears associated with potential negative effects on sea turtle nesting have served to promote the control and survey efforts presently underway in coastal areas of the Carolinas, Virginia, and Maryland.