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. Relatively little research has been published on fertilizer requirements of shrubs in sand soils of Florida and much of that has used chinese hibiscus ( Hibiscus rosa-sinensis ), a species that may be atypical for tropical and subtropical shrubs because of

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No other plant material captures that so-sought exotic and tropical motif as do palms ( Fig. 1 ). A natural and unique group, palms comprise the most distinctive plant materials in our landscape but differ from other woody landscape plants in their

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Tibouchina urvilleana is a flowering tropical shrub with large (60–80 mm diameter) violet-blue flowers borne in terminal branched panicles. The foliage is downy with red margins. Tibouchina blooms from mid-summer into late fall. The shrub withstands “a few degrees of frost” (1). Tibouchina has potential for wider use although container production has been limited since severe pruning is required to maintain its shape. Growth retardants may aid in commercial production of compact Tibouchina plants.

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Low temperature is acknowledged to be the single most important factor limiting the distribution of plants (70). Freezing damage to horticultural crops is a ubiquitous problem of major economic significance even in sub-tropical regions. Among the more commonly recognized types of freezing injury are sunscald and frost splitting of tree trunks, winter burn on conifer foliage, blackheart in stems of trees and shrubs, soil heaving damage and crown kill of herbaceous perennials, die-back in citrus, mid-winter kill of dormant flower buds, and spring and autumn frost damage of tender annuals, flowers and fruits.

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Heightened awareness of ecological concerns have prompted many municipalities to promote water conservation through landscape design. In central Arizona, urban residential landscapes containing desert-adapted plant species are termed xeriscapes, while those containing temperate or tropical species and turf are termed mesoscapes. Research was conducted to ascertain landscape plant species diversity, tree, shrub, and ground cover frequency; landscape canopy area coverage; and monthly irrigation application volumes for xeric and mesic urban residential landscapes. The residential urban landscapes were located in Tempe and Phoenix, Ariz., and all were installed initially between 1985 and 1995. Although species composition of xeric and mesic landscapes was generally dissimilar, both landscape types had comparable species diversity. Mesoscapes had significantly more trees and shrubs and about 2.3 times more canopy area coverage per landscaped area than xeriscapes. Monthly irrigation application volumes per landscaped surface area were higher for xeriscapes. Even though human preference for xeric landscape plants may be ecological in principle, use of desert-adapted species in central Arizona urban residential landscape settings might not result in less landscape water use compared with mesic landscapes.

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., Ligustrum L., Osmanthus Lour ., and Syringa L.) purposes. The genus Chionanthus has ≈100 species ( Chang et al., 1996 ; Wallander and Albert, 2000 ) distributed throughout tropical and subtropical areas worldwide but includes three temperate species

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Plumeria is a small genus of succulent trees and shrubs in the Apocynaceae native to tropical America. It is favored as a landscape ornamental in tropical and tropical regions due to its tolerance of hot, dry conditions, ease of propagation, and long season of bloom. Flowers of certain varieties are important components of leis in Hawaii. Numerous cultivars have been developed, chiefly from either seedling selections of P. rubra, a Mexican species, and P. obtusa, broadly distributed in the Caribbean basin, or hybrids between these species and among older cultivars. Little is known of the breeding behavior of the species in nature or cultivations, but very few of the cultivars set an abundant number of fruits. We used 21 microsatellite DNA (SSR) loci developed in our lab from Plumeria rubra to investigate the genetic relationships of 83 cultivars of Plumeria from a germplasm collection at the University of Hawaii, now duplicated in Miami. All 21 loci were highly polymorphic, with three to 15 alleles observed across the cultivar population. Six of the 21 loci exhibit heterozygote excess across the cultivars; the majority of the remaining 15 have an excess of homozygotes, suggesting that the cultivars are largely inbred. Clustering with Bayesian analysis suggests that there are five main groups represented among the cultivars, with varying degrees of admixture among the five. The data also suggest that identical genotypes have received different cultivar names at times. We are also analyzing seedling populations from fruits spontaneously set on several cultivars to determine if they are predominantly the result of self-pollination or out-crossing.

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Crapemyrtles (Lagerstroemia) are deciduous shrubs or trees with prolific summer flowers. Their popularity is due in large part to low maintenance requirements in sunny climates, wide range of growth habits, disease resistance, and bark characteristics, as well as having a long flowering period (up to 120 days). Once well-established, they are extremely tolerant to heat and drought. Lagerstroemia was first introduced to the southern U.S. from southeast Asia more than 150 years ago, and is comprised of at least 80 known species. Most modern cultivars are L. indica and L. fauriei hybrids. L. speciosa is a tropical crapemyrtle with very large flowers, but lacks cold hardiness. It is a vigorous plant, but only when grown in Hardiness zones 9 or 10. We recently established microsatellite markers for Lagerstroemia and evaluated their utility for verifying interspecific hybrids. Here we verify F1 hybrids between L. indica `Tonto', `Red River', and L. speciosa. We also genotyped two commercially available L. speciosa hybrids. Currently, we are using crapemyrtle SSRs for cultivar identification and germplasm conservation. Future research includes marker-assisted breeding to produce powdery mildew and flea beetle resistant cultivars, as well as improved growth habit and fall foliage color.

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This report describes an efficient in vitro regeneration protocol for H. patens (firebush), a heat-tolerant ornamental shrub native to tropical and subtropical America. Shoot cultures were initially established using shoot tips placed on MS-revised medium containing 2.3 μM 2,4-D, 2.3 μM kinetin, and 0.25% polyvinylpyrrolidone. Other types of explants (nodal and internodal segments, leaf pieces, floral buds) did not regenerate shoots when placed on this medium. Two-month-old plantlets derived from the shoot tips were subcultured on MS medium supplemented with 0.5 μM thidiazuron (TDZ), and within 3 to 4 weeks, some callus was produced at the root–shoot junction. When this callus, with a small portion of the root and shoots, was placed on MS medium with 0.05 μM TDZ and 0.01 μM ABA, prolific shoot formation occurred within 3 to 4 weeks followed by root formation. By regular subculturing every 5 to 6 weeks, hundreds of plantlets have been obtained over the past 3 years with no apparent decline in regeneration potential. Addition of activated charcoal (0.5%) to the culture medium has greatly improved growth of the plantlets.

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Interest in chemical modification of root systems of container-grown trees has increased in recent years with more widespread recognition of implications of root system architecture of container-grown trees on subsequent landscape performance. Initial research on Cu-based latex materials for application to interior container surfaces to avoid circled, matted, and kinked roots at container wall: media interfaces began with small forest tree liners in the late 1970s and early 1980s. Transfer of this technology to horticultural crops followed from the mid-1980s to the present. Testing has spread to a wide range of temperate and tropical landscape trees, shrubs, herbaceous annuals and perennials, interior foliage plants, and vegetable transplants. Inhibition of root elongation after contact with treated container surfaces is via a mild Cu toxicity, frequently resulting in a stimulation of lateral root proliferation proximal to the inhibited root tip, but responses vary with species, cultivar, media composition and pH, and Cu concentration and formulation. Early reports on root architecture effects were predominantly qualitative in nature. Quantitative studies on root architecture within treated containers have been less consistent in responses among species. Improvements in root regeneration, shoot growth, and water relations during post-transplant field establishment of trees grown in Cu-treated vs. non-treated containers have been documented for several species. Ecological (Cu leaching potential), technological (new applications), and economic (profitability) questions have arisen with increased use and availability of Cu-based container treatments and will be discussed.

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