Deciduous plants that are field-grown in nurseries are generally dug when dormant in late fall, winter, and spring. Each year, several million dormant rose plants (Rosa L. sp.) are dug bare-root from production fields in California and Arizona and shipped immediately to other states where they are planted in containers and forced to flowering for nationwide marketing. Although precautions are taken, significant plant moisture loss has been observed to occur during digging, shipping, and potting operations.
Plant moisture loss during postharvest handling is considered one of the major causes of poor regrowth or failure to regrow (Insley and Buckley, 1985; Lefevre et al., 1991; McKay, 1997). Desiccation tolerance depends on growth stage and is greatest when plants are dormant (Coutts, 1981; Englert et al., 1993; Murakami et al., 1990; Ritchie and Roden, 1985). Bare-root seedlings of Pinus radiata D.Don plants are prone to greater moisture loss during storage than container seedlings, and after only 1-d storage at 4 °C, reestablishment was significantly poorer compared with container seedlings (Mena-Petite et al., 2001). Packaged rose plants exposed to simulated marketing conditions (23 °C for 4 weeks) that led to moisture content of 28% to 43% had fewer numbers of new canes, fewer flowers, and, for some cultivars, greater mortality than plants held at 3 °C for 4 weeks with plant moisture of ≈50%. Growth of these roses was not evaluated until after the treated plants were field-grown for one full growing season (Welch and Cameron, 1990). When moisture loss from bare-root roses was minimized during cold storage through application of hot wax, plants started vegetative growth in 15 d compared with 30 d for control treatments (Schuch et al., 1995).
Desiccation tolerance varies greatly between taxa (Bates and Niemiera, 1994; Englert et al., 1993; Rebhuhn, 1985). Crataegus phaenopyrum Medic. and Prunus ×yedoensis Matsum., both in the Rosaceae, along with other species in both genera have been reported to be sensitive to desiccation during lifting, storage, and transplanting (Bates and Niemiera, 1994; Murakami et al., 1990). Garden roses were also reported to be more prone to desiccation compared with other deciduous plants (Toy and Mahlstede, 1959).
The tolerance for moisture loss below a critical threshold that affects survival varies by species. A critical level of postharvest moisture content for the survival of ‘Mister Lincoln’ rose plants was found to be between 33% and 41% when the treated plants were evaluated at the end of the first growth flush after potting (Pemberton and Roberson, 1990). For norway maple (Acer platanoides L.) and washington hawthorn that lost ≈20% of their fresh weight, survival dropped to 40% and plant dieback increased to 90% (Englert et al., 1993). In contrast, red oak (Quercus rubra L.) lost water at a lower rate and at 18% moisture loss resulted in 95% survival and less than 40% dieback (Englert et al., 1993). All colorado spruce (Picea pungens glauca Engelm.) survived when seedlings lost up to 25% fresh weight during cold storage, but no seedlings survived when water loss was higher than 60% (Lefevre et al., 1991).
The objective of this study was to determine how postharvest moisture loss from field-grown bare-root plants in an arid climate affects subsequent growth and flowering performance of containerized garden roses in a nursery production setting.
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