The discovery of auxins as plant growth regulating chemicals in the 1930s and their ability to stimulate adventitious rooting in stem cuttings marked a major milestone in the modern history of plant propagation. Basic and applied research conducted during the past 70 years has provided information regarding absorption and translocation of auxin in cuttings, as well as the effects of timing of auxin application, methods of auxin application, type of auxin, and concentration of auxin on the rooting response of cuttings. The basal quick-dip method, the powder application method, and the dilute soak method have been the most commonly used methods for applying auxin to cuttings in commercial horticulture over the past 7 decades, with the first two methods still in common use today. In addition, a wide variety of other auxin application methods have been reported beginning in the 1930s and continuing to the present. Some of these methods remain primarily of historical interest, several find limited use in commercial horticulture, and others show potential for greater use in the future. Opportunities exist for further development of auxin application techniques that can enhance plant quality, efficiency and productivity of the cutting propagation process, and worker safety. This review provides horticulturists, from the academic researcher to the commercial propagator, with an exploration of auxin application methods over the past 70 years, along with an examination of the physiological response of cuttings to applied auxin and an overview of issues leading to future opportunities.

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Silver reflective plastic mulches were compared with conventional bare-ground culture of yellow crookneck summer squash (Cucurbita pepo L. var. melopepo Alef.) for reducing aphids and the following mosaic virus diseases: cucumber mosaic, watermelon mosaic I and II, zucchini yellows mosaic, and squash mosaic. Plants grown on silver plastic mulch produced higher marketable yields than those grown on bare ground. Other colors (white, yellow, and black with yellow edges) of plastic mulch were intermediate in their effects on aphid population and virus disease reduction. Silver reflective mulch alone and silver reflective mulch with insecticide were superior to other colors of plastic mulch in reducing aphid populations. Silver reflective plastic mulch, with or without insecticide, resulted in 10 to 13 days delay in the onset of the mosaic diseases noted.

Petal anthocyanins were systematically identified and characterized by high-performance liquid chromatography (HPLC)–electrospray ionization–mass spectrometry (MS) coupled with diode array detection among nine wild herbaceous peony (Paeonia L.) species (15 accessions). Individual anthocyanins were identified according to the HPLC retention time, elution order, MS fragmentation patterns, and by comparison with authentic standards and published data. Six main anthocyanins, including peonidin-3,5-di-O-glucoside, peonidin-3-O-glucoside-5-O-arabinoside (Pn3G5Ara), peonidin-3-O-glucoside, pelargonidin-3,5-di-O-glucoside, cyanidin-3,5-di-O-glucoside, and cyanidin-3-O-glucoside (Cy3G), were detected. In addition to the well-known major anthocyanins, some minor anthocyanins were identified in herbaceous peony species for the first time. Detection of the unique anthocyanins cyanidin-3-O-glucoside-5-O-galactoside and pelargonidin-3-O-glucoside-5-O-galactoside in both Paeonia anomala L. and P. anomala ssp. veitchii (Lynch) D.Y. Hong & K.Y. Pan indicated these two species should belong to the same taxon. Pn3G5Ara was found only in European wild species and subspecies suggesting different metabolic pathways between European and Chinese accessions. Anthocyanins conjugated with galactose and arabinose were observed in the genus Paeonia for the first time. The North American species, Paeonia tenuifolia L., had high Cy3G content in flower petals. This anthocyanin composition is distinct from the anthocyanin composition in Asian and European species and possibly is responsible for the vivid red coloration in flowers.

`Formosa' azalea (Rhododendron indicum) was grown for 4 months in 7.6-L (2 gal) containers in four substrate blends: 100% pine bark (PB) (by volume), 1 PB: 1 cotton gin compost (CGC), 3 PB: 1 CGC, and 3 PB: 1 peat (PT) at three irrigation levels [600, 1200, and 1800 mL·d-1 (20.3, 40.6, and 60.9 floz/d)] in a polyethylene-covered greenhouse. Plants were evaluated for growth on a biweekly basis using a growth index. Roots were evaluated visually at the end of the study using a 0 (no root growth) to 5 (root bound) scale. Initial physical properties were determined and leachates were collected every 30 days. There was no difference in percent increase in growth across irrigation and substrate treatments. Visual root rating was greatest (4.5) for azaleas grown in 3 PB: 1 PT and least (3.5) in 1 PB: 1 CGC. The two PB/CGC blends improved water-holding capacity (WHC) in comparison to 100% PB, with 1 PB: 1 CGC exhibiting the greatest WHC among all four substrates. Bulk density was greatest with the CGC-amended substrates. Leachate pH tended to increase and electrical conductivity (EC) tended to decrease with increasing irrigation volume. Leachates from the CGC-amended substrates were less acidic and EC tended to be similar or greater than leachates from the 100% PB and 3 PB: 1 PT substrates.