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E.W. Bush, A.W. Fennel, W.A. Young, and T.J. Raiford

To promote both learning and horticulture, a 5 year pilot program was implemented with a collaborative effort between the Louisiana State University Horticulture Department and the University Laboratory School. The objective of this program was to develop a hands-on approach to learning which fostered self-discovery and a positive perception of horticulture. First graders were able to experiment in both the greenhouse and in the field with instruction in the classroom. Among the many concepts that the children were Introduced to, they benefitted most from being able to participate and observe the process from seeding to harvesting enabling them to work with the different types of seeds, media, and fertilizers. In the classroom, horticulture was Integrated in every subject of the first grade class. For example, the students learned math by measuring and counting the produce then making charts to report their findings. The result of the program was that the children did in fact obtain a positive perspective of horticulture while developing an awareness of the process of growth and development of horticultural crops. The first grade class received a national award for donating their produce to the local food bank in Baton Rouge.

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Michael W. Olszewski, Marion H. Holmes, and Courtney A. Young

There is a lack of quantifiable data concerning physical analyses specific to shallow-depth green roof substrates and their effects on initial plant growth. Physical properties were determined for green roof substrates containing (by volume) 50%, 60%, or 70% heat-expanded coarse slate and 30% heat-expanded fine slate amended with 20%, 10%, or 0% landscape and greenhouse waste compost. Each substrate also was amended with hydrogel at 0, 0.75, 1.50, or 3.75 lb/yard3. There were no differences in total porosity among substrates containing 0%, 10%, or 20% compost, although total porosity increased for all substrates amended with hydrogel at 3.75 lb/yard3. Container capacity increased in substrates containing 3.75 lb/yard3 hydrogel, except for substrates containing 10% compost where hydrogel had no effect. Aeration porosity decreased when 10% or 20% compost was added to substrates. Determination of aeration porosity at an applied suction pressure of 6.3 kPa (AP-6.3 kPa), indicated that AP-6.3 kPa was higher in substrates containing 0% compost than substrates containing 20% compost. Shoot dry weight and coverage area measurements of ‘Weihenstephaner Gold’ stonecrop (Sedum floriferum) and ‘Summer Glory’ stonecrop (Sedum spurium) were determined 9 weeks after plug transplantation into substrates. Both stonecrop species responded similarly to substrate amendments. Initial plant growth was greater in substrate containing 20% compost and 3.75 lb/yard3 hydrogel than nonamended substrate resulting in 198% and 161% higher shoot dry weight and coverage area, respectively. Alkaline heat-expanded slate and acidic compost components affected initial pH of substrates, but there was less variation among final substrate pH values. We conclude that compost and/or hydrogel amendments affected physiochemical properties following incorporation into slate-based green roof substrates, resulting in greater initial plant growth, and that these amendments may have practical applications for improving growing conditions on green roofs.

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Michael W. Olszewski, Courtney A. Young, and Joel B. Sheffield

Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald] and showy ticktrefoil [Desmodium canadense (L.) DC.] are legumes native to North America used during meadow restoration efforts. However, insufficient or slow germination or reduced emergence may result attributable to seedcoat-mediated reductions in permeability to water. The objective of this research was to determine the effectiveness of a single-speed electric scarifier lined with 40-grit sandpaper for increasing germination and seedling growth of two native legumes. Seeds of Illinois bundleflower and showy ticktrefoil were mechanically scarified for 3, 6, or 12 s before they were subjected to germination and vigor testing. After scarification, final germination percentage (FGP), germination rate, and uniformity at multiple temperatures (15, 20, and/or 20 to 30 °C) were improved for Illinois bundleflower. However, FGP decreased for showy ticktrefoil, whereas germination rate and uniformity increased. For both species, there was a decline in FGP with longer scarification durations. Illinois bundleflower seed subjected to scarification and accelerated aging (AA) had higher FGP than non-scarified seed subjected to AA (59% and 6%, respectively), whereas both scarified and non-scarified seed of showy ticktrefoil subjected to AA had low FGP (11% and 18%, respectively). Mechanical scarification increased electrical conductivity (EC) of leachates for both species, but scarified showy ticktrefoil seed subjected to AA resulted in the highest EC compared with all other treatments, indicating a reduction of vigor. Evaluation of a seedling grow-out test 3 weeks after sowing confirmed that emergence was enhanced after 3 s of mechanical scarification of Illinois bundleflower seed but that scarification of showy ticktrefoil seed decreased emergence and increased the number of abnormal seedlings. Mechanical scarification resulted in peripheral damage and seed tissue obliteration of both species as indicated by viewing with a stereomicroscope. We conclude that scarifier limitations caused excessive physical damage of showy ticktrefoil. For Illinois bundleflower, however, mechanical scarification using an electric scarifier increased emergence from 18% (non-scarified seed) to 77% after 3 s of scarification and FGP from 32% (non-scarified seed) to 87% after 3 s of scarification. Compared with responses from non-scarified Illinois bundleflower seeds, scarification treatment also resulted in 24% faster germination and 37% more uniformity.

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R.D. O'Barr, Wayne Sherman, W.A. Young, W.A. Meadows, Vernon Calcote, and Glenn KenKnight

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C.E. Johnson, J.T. Payne, W.A. Young, and E.W. Bush

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C.E. Johnson, J.T. Payne, W.A. Young, D.H. Picha, and W.R. Okie

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Kaylee A. South, Paul A. Thomas, Marc W. van Iersel, Cindy Young, and Michelle L. Jones

Phalaenopsis orchids are an increasingly popular potted house plant in the United States. New cultivars have a long display life in home environments, but these epiphytes are often overirrigated by consumers. Irrigating potted Phalaenopsis orchids weekly with ice cubes has been recommended as a simple solution to help consumers, but concern has been raised about whether the ice cubes will cause low temperature damage in these tropical plants. The effect of ice cube irrigation on the display life and quality of four cultivars of potted Phalaenopsis orchids was, therefore, evaluated. Irrigation treatments included weekly application of three ice cubes or the equivalent volume of room-temperature tap water. The longevity of individual flowers and the overall display life of the orchid plants were determined. Monthly measurements determined the volume of leachate in the outer decorative pots after irrigation. The quantum yield of photosystem II (ΦPSII) in roots and leaves was evaluated monthly to determine if photosynthetic efficiency was affected by the ice irrigation. The temperature in the orchid bark growing media during irrigation events was recorded, and a programmable antifreeze bath was used to determine the temperature at which damage to PSII was observed in orchid roots. The flower longevity and display life were unaffected by irrigation treatment. In general, the leachate volume over time was the same or lower in ice irrigated orchids compared with those irrigated with the same volume of water. The lowest temperature in the bark media irrigated with ice cubes was ≈11 °C, while controlled freezing experiments showed that damage to photosystem II in orchid roots did not occur until bath temperatures were below −7 °C. The internal temperature of roots in direct contact with ice cubes decreased to around 4 °C. Ice cube irrigation had no detrimental effects on the quality or display life of potted Phalaenopsis orchids growing in bark, demonstrating that ice cubes are a viable method of irrigating these tropical house plants.

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C.E. Johnson, J.T. Payne, M.L. Robbins, and W.A. Young

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R.E. Byers, J.A. Barden, R.F. Polomski, R.W. Young, and D.H. Carbaugh

Shading (92%) of `Redchief Delicious' apple (Malus domestics Borkh.) trees for 10-day periods from 10 to 20, 15 to 25, 20 to 30, and 25 to 35 days after full bloom (DAFB) caused greater fruit abscission than shading from 5 to 15, 30 to 40, 35 to 45, or 47 to 57 DAFB. Fruit 8 to 33 mm in diameter (10 to 30 DAFB) were very sensitive to 10 days of shade, even though fruit sizes of 6 to 12 mm are considered the most sensitive to chemical thinners. In a second test, shading for 3 days caused fruit thinning; 5 days of shade in the periods 18 to 23, 23 to 28, and 28 to 33 DAFB caused greater thinning than 11 to 16 or 33 to 38 DAFB. Shading reduced photosynthesis (Pn) to about one-third that of noncovered trees. Terbacil (50 mg·liter-1) + X-77 surfactant (1250 mg·liter-1) applied with a hand-pump sprayer 5, 10, or 15 DAFB greatly reduced fruit set and caused some leaf yellowing, particularly in the earliest treatments. Terbacil reduced Pn by more than 90% at 72 hours after application. Shoot growth of trees defruited by shade or terbacil was equivalent to defruited or deblossomed trees; ethephon (1500 mg·liter-1) inhibited tree growth and defruited trees. No terbacil residues were dectected in fruit at harvest from applications made 5, 15, 20, 25, or 30 DAFB. Eleven of 12 photosynthesis-inhibiting herbicides were also found to thin `Redchief Delicious' apple trees. Shading caused more thinning than terbacil at the later applications, which may reflect poorer absorption and/or lesser photosynthetic inhibition than when terbacil was applied to older leaves.

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C.E. Johnson, W.A. Young, J.E. Boudreaux, W.J. Bourgeois, F.J. Peterson, and P.W. Wilson