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Andrew L. Thomas and Denny Schrock

Hundreds of perennial plant species native to the midwestern United States have potential as ornamentals, but information on how best to use such plants in the landscape remains scarce. Many horticulturists are looking for species that perform well under low-maintenance conditions and that also attract and benefit desirable fauna, such as butterflies and birds. While many of our native plants may fit into this category, not all such species will meet aesthetic criteria for home landscapes. Some native species respond to seasonal changes in temperature and rainfall by browning or going dormant. Others have very specific site requirements for moisture, soil, and humidity that may be difficult to meet in an urban landscape, or their size, growth habit, or other characteristics may make them aesthetically undesirable in the typical home landscape. This study evaluated the performance of 67 plant taxa native to the midwestern United States selected for their promising potential in a low-maintenance landscape situation.

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Sharon Frey and Carolyn Robinson

Plants have been introduced into the United States intentionally as well as unintentionally as seeds and weeds. Technological advances, a mobile society, and our curiosity and desire to improve our landscapes have led to an ever-increasing invasive movement. These alien plants can jeopardize native populations, alter ecosystems, alter fire and water regimes, change the nutrient status, modify habitats, and cause significant economic harm. Today's public is unaware of the danger some non-native plants species pose to natural areas, thereby contributing to the lack of control for non-native invasive plants. This study looked at the knowledge and attitudes of Texas Master Gardeners as related to invasive species commonly used in landscaping. A web survey was made available to all Texas Master Gardeners that included pictures of plants along with their common and scientific names. Participants were asked to identify which they thought were invasive and contribute information regarding their knowledge of non-native invasive plants. Each of the invasive plants shown is on both the federal and the Texas Invasive Plant lists. Inquires were made concerning the occurrence of these plants in the participants' personal landscape and communities and their perceptions of each plant as an invasive threat. The purpose of the study is to determine if a relationship exists between knowledge, attitudes and perceptions of the participant and the occurrence of non-native invasive plants in the landscape. The results of this study will help determine factors that contribute to the lack of control for non-native invasive plants.

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Andrew Riseman, V.A. Sumanasinghe, Douglas Justice, and Richard Craig

We propose the name Exacum Styer Group for an interspecific population derived from several Sri Lankan Exacum taxa. Confirmation of hybrid status was determined by the appearance of either unique trait combinations or intermediate forms of traits originally represented by individual native taxa. Through 12 sexual generations, the proposed cultivar-group continues to exhibit these unique traits and now forms a cohesive fertile population.

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James C. Sellmer

Bringing Nature Home: How Native Plants Sustain Wildlife in Our Gardens. Douglas W. Tallamy. 2007. Timber Press, Inc., Portland, OR. 288 pages, with illustrations. $27.95, Hardcover. ISBN-13:978-0-88192-854-9. Bringing Nature Home is the first

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Margaret R. Pooler, Ruth L. Dix, and Joan Feely

The issue of invasive plants has become a concern to a variety of groups, including environmentalists, policymakers, and nurserymen. Although many surveys of invasive plants have been made, little research on the biology of hybridization has been conducted. Bittersweet (Celastrus) species serve as a good model system to test the effects of interspecific hybridizations since native and introduced species are found in the U.S. The American bittersweet (Celastrus scandens L.) is a deciduous climbing or twining shrub native to eastern and central North America. Although the bark has been used for medicinal purposes, the plant is cultivated as a nursery crop primarily for its bright red berries. In its natural habitat, native bittersweet is also an important source of food and cover for wildlife. Over the past several decades, populations of native bittersweet have declined to such low levels that some states are considering listing it as a threatened species. One reason for the rarity of American bittersweet in the wild is thought to be competition and possibly hybridization with an aggressive introduced species, oriental bittersweet (Celastrus orbiculatus Thunb.), which was introduced from Asia into the U.S. in 1860 as an ornamental. This plant can form dense, tangled, impenetrable thickets or climb small trees to girdle and smother them. It has been seen in at least 21 states since it was first recorded as an escape plant in 1912. Our objective was to determine whether oriental bittersweet can hybridize with native bittersweet, thus contributing to the loss of native populations in the United States. We performed controlled pollinations using C. scandens as the female parent and C. scandens or C. orbiculatus as the male parent. Although the intraspecific pollinations resulted in significantly more germinating seedlings than the interspecific crosses, the seedlings from the interspecific crosses had less seed dormancy and were more vigorous and more quick to vine than the intraspecific seedlings. These results indicate that the decline of the American bittersweet may be due to interspecific hybridizations with the invasive introduced species.

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P. M. Lyrene and W. B. Sherman

Abstract

V. myrsinites Lam. is most susceptible to canker among the blueberry species native to Florida and survives by resprouting from underground rhizomes. V. darrowi Camp suffers less canker damage than V. myrsinites, some mature colonies showing little or no damage but others being nearly destroyed by the disease. Most mature V. darrowi colonies in the State have some stems cracked and swollen by canker. Old native plants of V. ashei Reade and V. fuscatum Ait. show light to moderate canker damage in many parts of the State but both species are more resistant than the previous two. V. elliottii Chapm. shows no canker over much of its range in Florida, but localized populations have moderate to high infection. Only one cankered plant of V. arborewn Marsh, has been found, and no canker has been found on V. stamineum L.

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Jyotsna Sharma* and William R. Graves

Tolerance of shade, flooding, drought, and nutrient-poor substrate is desirable among ornamental plants installed in managed landscapes. Many attractive native taxa have not been evaluated for their resistance to environmental stressors. We assessed Florida corkwood (Leitneria floridana Chapman) in its natural habitat in four disjunct populations in the United States and tested the physical and chemical properties of the soil at the study sites. Measures at all sites were made within two weeks in late June, 2003. Leaf area, plant height, length of new shoots, and the rate of photosynthesis were higher among plants receiving more than 600 μmol·m-2·s-1 of photosynthetically active radiation (PAR) compared to plants that occurred where maximum PAR was lower. Soil texture ranged from clay loam to fine sand, and soil pH across sites was 4.5 to 6.6. Concentration of nitrate-nitrogen, phosphorus, and potassium ranged from 3 to 75 mg·L-1, 7 to 11 mg·L-1, and 3 to 64 mg·L-1, respectively. Bases of plants in Florida were submersed in water, while soil moisture percentages in Missouri and Texas were 6 to 30. The apparent tolerance of L. floridana to shade, low and high soil moisture, and nutrient-poor soil in native habitats indicates that it could be used in a wide range of managed landscapes. Its capacity to adapt to shade may permit the use of L. floridana as an understory species in managed landscapes, but stewards of natural areas may need to maintain open sites within its native habitat to allow expansion of populations. Because this assessment of L. floridana included native populations across the natural range of the species, our results are uniquely suited for both horticultural and ecological interpretation and application.

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J.F. Hancock, P.W. Callow, S.L. Krebs, D.C. Ramsdell, J.R. Ballington, M.J. Lareau, J.J. Luby, G.P. Pavlis, M.P. Pritts, J.M. Smagula, and N. Vorsa

Flower bud and leaf samples collected from a wide range of native North American Vaccinium populations were tested for the presence of blueberry shoestring virus (BBSSV) using the enzyme-linked immunosorbant assay. The highest disease incidence was found in Michigan (14%), although a few positive samples also were found in Virginia, New Jersey, Maine, Ontario, and Quebec. Of seven species tested, only V. corymbosum L. and V. angustifolium Ait. were infected with BBSSV.

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Sloane M. Scheiber, Richard C. Beeson, and Heather Bass

Native plants are often promoted as an approach for water conservation in urban landscapes. However, information regarding plant water needs is based primarily upon anecdotal observations of plant performance. Direct comparisons between native and introduced species using physiological measures of plant water stress are unavailable to support or refute such recommendations. Ligustrum japonicum and Myrica cerifera, representing an introduced and native species, respectively, were transplanted into a fine sand soil to evaluate establishment rates and growth characteristics under two irrigation regimes. Each species was irrigated either daily or every 3 days and received 1.3 cm of irrigation per event for 8 months after transplant. Predawn, midday, and dusk water potentials were recorded on three consecutive days monthly, with cumulative stress intervals calculated. Height, growth indices, shoot dry mass, root dry mass and leaf area were also recorded. Water potential was significantly influenced by day of water stress level. On days without irrigation, water stress was generally greater and affected growth. Myrica irrigated daily had the greatest growth, yet plants receiving irrigation every 3 days had the least growth and greater leaf drop. In contrast, for Ligustrum there were no differences between irrigation regimes in growth responses except for growth index.

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Guillermo Cardoso, Roger Kjelgren, Teresa Cerny-Koenig, and Rich Koenig

Low water landscapes are increasing popular and important in the urban areas of the Intermountain West (IMW). Perennial wildflowers are an essential part of low water landscapes, and are a dominant plant type in IMW native habitats. We compared pot-in-pot (PIP) vs. conventional above-ground (CAG) production of six IMW native wildflower species, Mirabilismultiflora, Aquilegia caerulea, Penstemon palmeri, Polemonium foliosissimum, Sphaeralcea grossularifolia, and Penstemonstrictus in #1 (4-L) containers. Media temperature, container-plant water loss, stomatal conductance, and growth were measured during two production cycles per year over 2 years. Growing medium temperatures in the PIP system averaged 10 °C cooler than in the CAG system. Consistent with cooler growing media, overall water loss of PIP-grown plants averaged 10% lower than plants grown in the CAG production system. Lower growing media temperatures apparently affected transpiration, as stomatal conductance was about 60% higher in the PIP system as compared to the CAG-grown plants. The integrated effect of lower growing media temperatures on plant performance resulted in about one-third greater top and root growth for plants growing in the PIP system compared to those in the CAG system. Pot-in-pot production may be an economically suitable nursery system for producing IMW native perennial wildflowers by reducing water loss and enhancing growth.