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- Author or Editor: Stuart L. Warren' x
The length of time between transplanting and subsequent new root initiation, root growth rates, and root growth periodicity influences the ability of woody ornamentals to survive transplanting and become established in the landscape. Research was conducted to compare root growth of a difficult-to-transplant species, Kalmia latifolia L. (mountain laurel), to that of an easy-to-transplant species, Ilex crenata Thunb. (Japanese holly), over the course of 1 year. Micropropagated liners of `Sarah' mountain laurel and rooted stem cuttings of `Compacta' holly were potted in 3-L containers. Plants were grown in a greenhouse from May to September, at which time they were moved outside to a gravel pad, where they remained until the following May. Destructive plant harvests were conducted every 2 to 4 weeks for 1 year. At each harvest, leaf area, shoot dry weight (stems and leaves), root length, root area, and root dry weight were determined. Throughout the experiment, shoot dry weight and leaf area were similar for the two species. New root growth of `Compacta' holly and `Sarah' mountain laurel was measurable 15 and 30 days after potting, respectively. Root length and root area of `Sarah' mountain laurel increased during May through December but decreased during January through May. Root length and root area of `Compacta' holly increased linearly throughout the course of the experiment. Final root: shoot ratio of `Sarah' mountain laurel was one-ninth that of `Compacta' holly. Results suggest that poor transplant performance of mountain laurel in the landscape may be related to its slow rate of root growth.
Eight taxa of Salvia L., representing broad geographic origin and diversity within the genus, were grown under long day conditions for 36 d at 15-h days of 20, 25, 30, 35, or 40 °C and 9-h nights of 15 or 25 °C. Taxa of European origin displayed broader tolerance to high day temperatures (DTs) with the lowest relative reduction in growth and net photosynthesis (Pn) occurring at DTs 30 °C or greater compared with those native to North and South America. Salvia splendens Sell. ex Roem. & Schult. (scarlet sage) was particularly intolerant of high temperatures with all plants dying at days of 40 °C. All plants of S. nemorosa L.‘Ostfriesland’ (‘Ostfriesland’ wood sage), S. pratensis L. (meadow sage), and S. × sylvestris L. ‘Mainacht’ (‘May Night’ salvia) survived at days of 40 °C with no visual signs of injury, whereas all other taxa except S. splendens exhibited stunted, contorted growth with foliar chlorosis and necrosis at 40 °C. Day temperature exerted the primary effect on top growth, root growth, and Pn of all taxa. Night temperature effects were significant for some taxa but were of less importance than day temperature.