JOBNAME: horts 43#7 2008 PAGE: 1 OUTPUT: October 22 16:06:39 2008 tsp/horts/175583/02964 HORTSCIENCE 43(7):2124–2128. 2008. difficulty to overwinter the newly rooted cuttings (Flemer, 1982; Perkins and Bassuk, 1995). Cuttings of Japanese Stewartia gener- Rooting and Overwintering Stem ally root satisfactorily but fail to successfully overwinter and grow the next spring. In most Cuttings of Stewartia pseudocamellia of the cases, they put forth a new flush of growth, which ultimately ceases to grow and Maxim. Relevant to Hormone, withers off (Smalley and Dirr, 1986; Stimart and Goodman, 1985). Gradual decaying of the root system is also observed. Meanwhile, Media, and Temperature successful propagation has been carried out Ajay Nair1,2, Donglin Zhang, and John Smagula in Stewartia ovata (Cav.) Weatherby (Curtis Department of Plant Soil and Environmental Sciences, University of Maine, et al., 1996). Micropropagation has been successfully carried out in Theaceae using 108B Deering Hall, Orono, ME 04469 nodal segments as explants (Samartin et al., Dongyan Hu 1986), although in Stewartia pseudocamellia, the process needs to be further investigated to Beijing Botanical Garden, Wofosi Road, Beijing, China 100093 produce multiple microcuttings per nodal Additional index words. Japanese Stewartia, KIBA, Promix, propagation, semihardwood, segment (McGuigan et al., 1997). Stewartia pseudocamellia Although sufficient carbohydrate storage is important for winter survival of cuttings Abstract. Stewartia pseudocamellia Maxim. (Japanese Stewartia), a member of Theaceae (Smalley et al., 1987), starch concentration in (tea family), is an excellent garden plant with ornamental features for all four seasons. stems of the cuttings is not always related to Reproduction difficulty, however, limits its popularity. We conducted three experiments survival (Apine and Kondratovicˇs, 2005). In to ascertain the optimum conditions needed for rooting and subsequent overwintering Stewartia, insufficient carbohydrates in the of semihardwood Stewartia pseudocamellia cuttings. Cuttings were collected in July cuttings cannot be accounted for low over- and prepared for rooting using two types of hormones (KIBA quick dip and Hormodin winter survival because the cuttings that even powder) and three media (Perlite + ProMix, Perlite + Perennial Mix, or Perlite + ProMix + grew after rooting did not have higher car- Perennial Mix). Rooted cuttings were overwintered at four different temperatures. The bohydrate content in them (Perkins and best overwintering temperature was 5 8C, at which 65.6% of newly rooted cuttings Bassuk, 1995). survived. Temperatures lower than –12.2 8C were detrimental to the plants. Without cold An interesting fact would be to examine treatment, only 21.9% of the rooted cuttings survived, which was three times lower than the effect of rooting hormone and rooting those that received 5 8C treatments. Plants rooted in Perlite + Perennial Mix had 61.8% media overrooting and subsequent overwin- overwintering survival, which is significantly higher than Perlite + ProMix. The quality tering. Higher concentration of auxins could of roots, indicated by total root length per cutting, was higher (104.3 cm) with Perlite + lead to ethylene biosynthesis, increased defo- Perennial Mix, but not statistically significant. Cuttings treated with rooting hormones liation, and poor budbreak (Sun and Bassuk, had higher rooting percentages (71.9% to 93.6%) as compared with the control (53%). 1993). In Stewartia ovata, optimum rooting For the same concentration (8000 mgÁL–1), liquid (KIBA) and liquid + powder (KIBA + percentage was recorded at 2000 mgÁL–1 indole-3-butyric acid) rooting hormones resulted in better rooting percentages than and 4000 mgÁL–1 concentrations of indole- powder (Hormodin) alone, although there was no statistical difference in rooting 3-butyric acid (IBA) (Curtis et al., 1996). percentages among rooting hormone treatments. The best hormone for subsequent Struve and Lagrimini (1999) found that a overwintering survival was the combination of quick dip (5000 mgÁL–1 KIBA) and pretreatment with ascorbic acid and caffeic Hormodin #2 (0.3% a. i.; equivalent to 3000 mgÁL–1). It resulted in 64.2% survival, acid followed by a lower concentration of significantly higher than for KIBA quick dip (8000 mgÁL–1 a.i.) or Hormodin #3 (0.8% IBA dip (100 mgÁL–1) can provide equally a. i.; equivalent to 8000 mgÁL–1) alone. Our results suggest that reproduction (rooting and good rooting percentages in Stewartia pseu- overwintering) of Stewartia was affected by many factors. We recommend rooting docamellia cuttings. Not much work has been Stewartia in media that has good aeration and moderate water-holding capacity and done to study the effect of hormone formula- overwintering them at ’5 8C. tion on rooting and subsequent overwintering. Overwintering temperature is also a crit- ical factor in successfully overwintering Stewartia is a member of tea family 1975). This tree performs well in U.S. rooted cuttings (Donnelly and Yawney, (Theaceae) and has eight to 21 species Department of Agriculture zone 6 to 8, but 1972). Various studies have been initiated depending on authors (Li, 1996; Prince and also grows satisfactorily in zone 5 (Dirr, in Acer (Smalley et al., 1987), Quercus Parks, 2001; Spongberg, 1974). Japanese 1998). Propagation of Stewartia pseudocamel- (Drew et al., 1993), and Cornus (Flemer, Stewartia is a popular ornamental plant with lia from seed is difficult and time-consuming 1982) to find the optimum overwintering camellia-like flowers, excellent fall color, as a result of complex dormancy mechanisms storage temperature. Air temperatures rang- and exfoliating winter bark (Dirr and Heuser, (Curtis et al., 1996). Seeds are described as ing from 1 to 5 °C have been found optimum 1987; Hohn, 1994; Spongberg and Fordham, ‘‘double dormant’’ with the embryo and its for overwintering rooted cuttings of Stewar- surrounding integuments suspected of main- tia spp. (Fordham, 1982; Gouveia, 1991, taining the dormant state (Hartmann et al., 1995). Curtis et al. (1996) found that the 2002). Dormancy can, however, be overcome optimum overwintering air temperature and Received for publication 24 Apr. 2008. Accepted by desiccation avoidance, gibberellic acid storage duration for Stewartia ovata was 6 °C for publication 22 July 2008. treatment, and warm and cold stratification for 10 weeks. We thank Arnold Arboretum, Jamaica Plain, MA, (Oleksak and Struve, 1999). Propagation by Media plays an important role in the entire for providing Stewartia cuttings for the conduct of stem cuttings is the most commonly used process of root growth and development once this research. asexual method to regenerate many woody they have emerged. Rooting media could also 1Current address: Department of Horticulture, A432 PSSB, Michigan State University, East ornamental plants. There have been a number affect the overwintering survival rate of the Lansing, MI 48824 and Maine Agriculture and of attempts to propagate Stewartia pseudo- plant. Meldrum (1979) reported that adequate Forestry Experiment Station Publication #3017. camellia by stem cuttings without much medium aeration was an important factor in 2To whom reprint requests should be addressed; success. The limitation, toward cutting prop- successful rooting of camellia. Fordham (1982) e-mail [email protected] agation of Stewartia pseudocamellia, is the and Dirr and Heuser (1987) recommended 2124 HORTSCIENCE VOL. 43(7) DECEMBER 2008 JOBNAME: horts 43#7 2008 PAGE: 2 OUTPUT: October 22 16:06:40 2008 tsp/horts/175583/02964 PROPAGATION AND TISSUE CULTURE rooting Stewartia cuttings in sand:perlite tings kept outside were covered with micro- procedure from SAS version 8.1 (SAS Insti- (1:1, by volume) and allowing the rooted foam on which snow accumulated. Electronic tute Inc., Cary, NC). Mean separation was cuttings to overwinter in the same media. data loggers were placed in all four locations. carried out using the least significant differ- Media amendments like dolomitic lime Cuttings were consolidated from all locations ence method at an alpha 0.05 level. (Curtis et al., 1996) and calcium (Smalley and brought inside the greenhouse on 28 Mar. and Avanzato, 1992) did not show any 2003. Survival rate was recorded based on the Results and Discussion significant effect in rooting when compared emergence of the new growth and health of with media without amendments. Applica- the cutting. Overwintering temperature. Temperature tion of nitrogenous fertilizer before overwin- Rooting hormone experiment. On 27 June played an important role in survival and ter storage has been found detrimental to 2003, semihardwood cuttings were collected overwintering of newly rooted cuttings. The successful overwintering (Curtis et al., 1996; in the same manner as described previously best overwintering temperature was 5 °C, at Goodman and Stimart, 1987). In this study, from the Arnold Arboretum of Harvard Uni- which 65.6% of the rooted cuttings survived we focused on effect of rooting hormone versity in Jamaica Plain, MA. Cuttings were (Fig. 1). Research done by Curtis et al. (1996) (type and formulation), media characteris- prepared similar to the overwintering tem- explained that chilling requirement is neces- tics, and overwintering temperature on root- perature experiment and their basal ends sary for both budbreak and shoot growth in ing and surviving of Japanese Stewartia. were treated with water (control treatment) Stewartia ovata. The duration of the treat- and three