Physiological dormancy is com- After-ripening, Stratification, and Perigynia mon in the and may be Removal Enhance Pennsylvania overcome or reduced by one or more of the following treatments: 1) after- Sedge Germination ripening (dry storage of seeds under ambient temperatures before sowing), 1 2) GA3, and 3) cold stratification Esther E. McGinnis and Mary H. Meyer (Baskin and Baskin, 1998, 2004). Broom sedge ( scoparia) germi-

ADDITIONAL INDEX WORDS. Carex pensylvanica, dormancy, propagation, nation was enhanced by up to 2 years Cyperaceae, achene of after-ripening (Larson and Stearns, 1990). Elongated sedge (Carex elongata) SUMMARY.Pennsylvaniasedge(Carex pensylvanica) has horticultural and restoration and remote sedge (Carex remota)in- potential, but the achenes are difficult to germinate due to complex dormancy creased germination following after- requirements. This study identified treatments to overcome physiological dormancy and determined light and temperature requirements for optimum germination. ripening in comparison with fresh We first tested the effects of perigynia removal and light on achene germination. In the achenes (Schutz, 1997b). However, second experiment, achenes were subjected to varying durations of dry-cold or some wetland Carex species had dry-warm storage conditions and a presowing soak in gibberellic acid (GA3). In higher germination percentages when a third experiment, we studied whether storage conditions, cold stratification, and stored cold and moist (Budelsky and sowing temperatures affected germination. Pennsylvania sedge germination was Galatowitsch, 1999). improved by dry-warm storage, perigynia removal, cold stratification, and Although GA3 failed to stimulate germination in light. germination in black and white sedge (Carex albonigra), ebony sedge [Carex ebenea (Amen and Bonde, ennsylvania sedge is commonly published, and native nurseries 1964)], and hood’s sedge [Carex used for forest restoration (Mottl propagate by division. Over- hoodii (McDonough, 1969)], it has Pet al., 2006) and has horticul- coming dormancy and understanding been shown to increase germination tural potential as a shade-tolerant germination requirements are essen- for other monocots such as sand rye- groundcover and low-maintenance tial for economically propagating grass [Leymus arenarius (Greipsson, lawn species (Darke, 2007). This her- pennsylvania sedge on a commercial 2001)], green needlegrass [Stipa vir- baceous perennial is native to dry de- basis. idula (Fulbright et al., 1983)], east- ciduous forests of the eastern half of Few Carex species exhibit physi- ern gamagrass [Tripsacum dactyloides temperate North America (Gleason cal dormancy or other germination (Rogis et al., 2004)], and four Aus- and Cronquist, 1991). It produces barriers as a result of their unique tralian grass species (Hagon, 1976). attractive slender leaves that form morphology. Carex are distinguished In contrast to GA3 pretreatment, cold a 12-inch mound of foliage that ex- from other genera within the Cyper- stratification has been shown to success- pands through long and short rhi- aceae by a bladder-like sac called the fully alleviate physiological dormancy zomes (Bernard, 1990) to form mats perigynium (perigynia, plural) that in many Carex species (Hoag et al., of 3 m2 (Mottl et al., 2006). Unlike tightly adheres to the hard pericarp 2001; Kettenring and Galatowitsch, most lawn species, it thrives in dry of the achene (Amen and Bonde, 2007a, b; Schutz and Rave, 1999). partial shade and is uniquely suited to 1964). The perigynium prevents ger- Although the most effective stratifi- the competitive environment under mination in nebraska sedge (Carex cation temperatures for Carex species large trees. Pennsylvania sedge also nebrascensis) and northwest territory can vary, temperatures below 12 C provides spring interest because it sedge (Carex utriculata) (Hoag et al., are most effective (Brandel and Schutz, blooms in mid-April to mid-May in 2001; Jones et al., 2004). In other 2005). Optimum stratification dura- southern Ontario and in the northern cases, Carex species respond to tradi- tion may range from 0.5 to 6 months United States (Crins and Ball, 1983). tional physical dormancy treatments for Carex species (Kettenring and Achenes ripen and dehisce in June in such as acidic scarification (Ishikawa Galatowitsch, 2007a). Minnesota (Table 1). Difficulties in et al., 1993) or pericarp nicking Pennsylvania sedge may have ad- achene germination limit the use of (Amen and Bonde, 1964). It is un- ditional germination requirements. A pennsylvania sedge for large horti- known whether pennsylvania sedge light requirement enables woodland cultural and restoration projects. exhibits physical dormancy or other Carex species to take advantage of No germination protocol has been germination barriers. gaps in leaf litter on the forest floor

Department of Horticultural Science, University of Minnesota, 305 Alderman Hall, 1970 Folwell Ave- nue, St. Paul, MN 55108 Units We thank Alan Wade from Prairie Moon Nursery, To convert U.S. to SI, To convert SI to U.S., Winona County, MN, for donating achenes and plant multiply by U.S. unit SI unit multiply by material for this experiment. 0.0929 ft2 m2 10.7639 Mention of a trademark, proprietary product, or 3.7854 gal L 0.2642 vendor does not imply endorsement by the University 2.54 inch(es) cm 0.3937 of Minnesota or its approval to the exclusion of other 16.3871 inch3 cm3 0.0610 suitable products or vendors. 1 ppm mgÁL–1 1 1Corresponding author. E-mail: [email protected]. (F – 32) O 1.8 F C(1.8·C) + 32

• April 2011 21(2) 187 RESEARCH REPORTS

Table 1. Origin and collection month of ripe pennsylvania sedge achenes used in University of Minnesota germination experiments, 2005 and 2006. Location Address Collection mo. Prairie Moon Nursery Section 15, Township 105N, Range 7W, June 2005, 2006 Winona County, MN University of Minnesota, Section 17, Township 116N, Range 23W, June 2006 Landscape Arboretum Carver County, MN Lebanon Hills Regional Park Sections 34 and 35, Township 27N, June 2006 Range 19W, Dakota County, MN Cedar Creek Natural History Area Section 34, Township 34N, Range 23W, June 2006 Anoka County, MN

or in the deciduous forest canopy required for the experiments; there- achenes were placed on top of the (Vellend et al., 2000). Germination fore, mature achenes were collected sand in each dish. The sand was of Carex species increased when im- from three additional locations in moistened with deionized water, and bibed achenes were exposed to white Minnesota (Table 1). In both years, more water was added as needed. fluorescent light (Kettenring et al., filled achenes were separated from Four petri dishes (four replications) 2006; Schutz and Rave, 1999). In a unfilled achenes using an air column for a total of 60 achenes were assigned groundcover study, the frequency of separator and tested for viability using to each treatment. All four petri pennsylvania sedge decreased under a 1% solution of 2,3,5-triphenyltetra- dishes were kept in a clear plastic tree canopy compared with clearings zolium chloride as described in Grabe bag (1 gal) to prevent excessive evap- (Collins and Good, 1987). Optimum (1970). Viability percentages ranged oration. The entire experiment was germination temperature has not been from 77% to 81% in both years. repeated 1 week later. identified for pennsylvania sedge. Eu- Because of the similarity of viability, Achenes exposed to white light ropean temperate sedges typically re- 2006 achenes were combined. The were placed in a growth chamber quire warm temperatures (>28 C) for total number of achenes per petri dish (Environmental Growth Chambers, germination (Grimes et al., 1981). was multiplied by the estimated via- Chagrin Falls, OH) and subjected to Schutz and Rave (1999) reported that bility percentage, and this number 200 mmolÁm–2Ás–1 of irradiance under a diurnally fluctuating temperature was deemed to be the maximum cool white fluorescent bulbs (model regime also enhances germination of possible germination per dish. F72T12/CW/VHO; Philips Light- some Carex species because this mimics EXPT.1:PERIGYNIA REMOVAL ing, Somerset, NJ) for 12 h per day, spring temperatures. Alternating day AND LIGHT EXPOSURE. This experi- with alternating 26 C, 10-h days/ and night temperatures of 27 and ment was conducted in 2006 with 18 C, 10-h nights with a 2-h transition 15 C increased germination for un- achenes that had been stored dry at period between temperatures. Achenes stratified achenes for the majority of 22 C, 50% relative humidity (RH) with no light exposure were placed in 12 temperate North American wet- for 8 weeks. The achenes were divided the same growth chamber, but petri land Carex species (Kettenring and for the following four treatments: 1) dishes were double wrapped in alumi- Galatowitsch, 2007a). intact perigynia, no light; 2) intact num foil to prevent light penetration. The objectives of this project perigynia, exposure to white light; 3) Germination counts were conducted were to test whether pennsylvania removed perigynia, no light; and 4) daily or every second day for 8 weeks. sedge germination is enhanced by removed perigynia, exposure to white Germinated seedlings were periodi- treatments designed to overcome light. Perigynia were removed by cally removed. Counts for the dark germination barriers posed by the rubbing the achenes in a hand trough treatments were made in a dark room perigynia and by the physiological between two layers of hard dimpled under low intensity green light. dormancy. In addition, we sought to rubber. The friction from the hand EXPT.2:STORAGE TEMPERATURE, determine optimum light and sowing trough removed the perigynia but did DURATION, AND GA3. Experiment 2 temperatures. We hypothesized that not scarify the exterior of the achene. was conducted in 2006 with achenes achene germination would be im- While light sanding with 100-grit that were stored dry at 22 C, 50% proved by 1) perigynia removal, 2) sandpaper is an accepted method RH for 5 weeks. Achenes were further presence of white light, 3) after-rip- for removing perigynia (Hoag et al., stored COLD (4 C, 8% RH), or ening, 4) GA3 pretreatment, 5) cold 2001), pennsylvania sedge achenes WARM, (22 C, 40% average RH) stratification, and 6) diurnally fluctu- crumble if they are lightly rubbed for an additional 4, 8, or 16 weeks. ating temperatures. with sandpaper (E.E. McGinnis, un- Thus, the total dry storage time was published data); therefore, scarifica- 9, 13, or 21 weeks. In addition to Materials and methods tion was not attempted. storage temperature and duration, a 2 In 2005, Prairie Moon Nursery Each 5.0 · 1.2-cm petri dish GA3 application constituted the third (Winona County, MN) provided (Fisher Scientific, Pittsburgh, PA) factor. freshly collected achenes (Table 1). was filled with 18.5 cm3 of sterilized At the conclusion of the storage In 2006, Prairie Moon Nursery could fine quartz sand (Industrial Quartz; treatments, perigynia were removed only provide 25% of the achenes Unimin, LeSueur, MN). Fifteen as described in Expt. 1. Achenes were

188 • April 2011 21(2) surface disinfected using a 30-s soak in each of the four petri dishes per germination. Highest percent germi- in 10% chlorine bleach solution and treatment in 2005; in 2006, because nation occurred when the perigynia then briefly rinsed, first in tap water of limited seed availability, only 15 were removed and when the achenes and then in distilled water. (The pre- achenes were sown in each of four were exposed to white light (Fig. 1), vious experiment did not use bleach petri dishes per treatment. Germi- although germination was still below disinfection because it may have in- nated achenes were counted daily or 35%. Previous research showed many terfered with potential germination every second day for 8 weeks. Carex species are either light obligate inhibitors in the attached perigynia.) STATISTICAL ANALYSIS. Data were or greatly benefit from light after After disinfection, one-half of the evaluated using analysis of variance (R sowing (Kettenring et al., 2006; Schutz achenes were soaked for 24 h in 500 Development Core Team, 2006). For and Rave, 1999). From a germination –1 mgÁL GA3 (ProGibbÒ T&O; Valent all experiments, the response variable mean of 21% in light, payson’s sedge BioSciences, Libertyville, IL); the was the germination proportion, (Carex paysonis)germinatedatless remaining 50% of the achenes were which was defined as the number of than 1% in complete darkness, and also soaked in distilled water as the control. germinated achenes divided by the when buried at a mere 0.5 cm, germi- Using a 2 · 3 · 2 factorial design, all number of viable achenes. Germina- nation was greatly reduced (Haggas treatment combinations were tested tion was defined by emergence of et al., 1987). Ebony sedge achenes for final germination percentage. Four radical and hypocotyl. Based on the germinated at 75.8% under fluorescent replications of 15 achenes each were binomial distribution of the germina- lights but only at 0.8% in darkness assigned to each treatment, and the tion proportions, the data were arcsin– (Amen and Bonde, 1964). In a Ger- entire experiment was repeated in time square root transformed (Snedecor man study of 32 temperate Carex 1 week later. Media, growth chamber and Cochran, 1989). Our sources of species, 2.07% of all unstratified conditions, and data collection are variation were fixed in all experiments. achenes germinated in darkness un- described in Expt. 1. The third experiment was conducted der a diurnally fluctuating tempera- EXPT.3:STORAGE, COLD STRATI- in both 2005 and 2006. Because of ture regime (Schutz and Rave, 1999). FICATION, AND SOWING TEMPERATURE. heterogeneity of variance between the Germination of forest Carex spe- This experiment was conducted in 2 years of the third experiment, the cies is not only inhibited by complete both 2005 and 2006, using a 2 · data for each year were analyzed and darkness, but it is also inhibited by 3 · 3 factorial design. The first factor discussed separately. For figures, the dense plant canopies that reduce the compared 5 months of storage, either germination proportions were back- red-to-far red ratio (Kettenring et al., 1 month WARM (22 C and 50% transformed and reported as percent- 2006) and factors that partially re- RH) followed by 4 months COLD ages. Multiple mean comparisons were duce irradiance such as leaf litter and (4 C and 8% RH) or 2 months WARM conducted using Fisher’s protected soil coverage. In a field study of two (22 C and 50% RH) followed by 3 least significant difference test. Means European wet-forest species, remote months COLD (4 C and 8% RH). were considered significant at the P < sedge and elongated sedge germi- Cold, moist stratification duration 0.05 level. nated in a deciduous forest almost consisted of 0, 1, or 2 months. The exclusively during late April and final factor compared diurnally fluc- Results and discussion earlyMaybeforethecanopyregen- tuating temperatures with a constant EXPT.1:PERIGYNIA REMOVAL erated (Schutz, 1997a). In another sowing temperature: 1) 26 C day/ AND LIGHT EXPOSURE. Perigynia re- field study, leaf litter inhibited the 18 C night, 2) 30 C day/14 C moval and light exposure signifi- germination of fibrousroot sedge night, or 3) constant temperature of cantly increased germination (Fig. 1). (Carex communis), broadleaf sedge 22 C. Intact perigynia and darkness inhibited (Carex platyphylla), and back’s Perigynia were removed, and achenes were disinfected. Cold strat- ification consisted of wrapping 15 or 30 achenes in filter paper and bury- ing them in a container of SB 500 High Porosity Mix (Sun Gro, Van- couver, BC, Canada). Containers were watered to saturation and placed in agrowthchamberataconstant4C for 1 or 2 months. The control treat- ment was immediately sown on sand in petri dishes under conditions de- scribed below. After stratification, achenes were sown in three separate growth cham- bers with day/night temperatures of Fig. 1. The effect of perigynia removal and light exposure on germination of 2006 pennsylvania sedge achenes at the University of Minnesota, MN. Half of 26 C/18 C, 30 C/14 C, and –2 –1 the achenes had their perigynia removed, while the other half were left intact. constant 22 C with 200 mmolÁm Ás Achenes were germinated under white fluorescent light or in darkness. Error of white fluorescent light for 12-h bars represent SE. Mean values labeled with different lowercase letters were days timed to coincide with day tem- significantly different according to Fisher’s protected least significant difference peratures. Thirty achenes were sown test at P £ 0.05 (n = 12 viable achenes, eight replications).

• April 2011 21(2) 189 RESEARCH REPORTS sedge (Carex backii) (Vellend et al., warm temperatures before sowing, it they were previously exposed to a 2000). Pennsylvania sedge capitalizes is unlikely to benefit from cold, wet warm storage period of 2 months as on disturbances that increase general storage conditions because of its hab- opposed to 1 month. In contrast, irradiance levels and the red-to-far red itat restrictions. Pennsylvania sedge when the warm storage period was ratio such as canopy openings (Collins typically inhabits dry to mesic woods increased from 1 month to 2 months, and Good, 1987) [e.g., clear-cutting and prairies (Hipp, 2008). germination of 1-month stratified of jack pine (Pinus banksiana)forests Gibberellic acid pretreatment had achenes increased significantly across and fire (Abrams and Dickmann, no effect on pennsylvania sedge germi- all sowing temperatures (Fig. 3). Two 1984)] and exotic earthworm con- nation. Our GA3 results were not dis- months of warm storage may have sumption of leaf litter (Hale et al., positive because we tested only one alleviated physiological dormancy 2008). Achenes may have evolved to concentration. However, GA3 failed enough to allow for maximum germi- germinate best in areas of high irradi- to stimulate germination in two pre- nation after only 1 month of cold ance and favorable red-to-far red ratios. vious studies on Carex species (Amen stratification. Overall in 2005, achenes This would allow pennsylvania sedge and Bonde, 1964; McDonough, that were cold-stratified for 2 months to germinate during spring before 1969). and germinated at a constant 22 Cor the forest canopy closes and during EXPT.3:STORAGE, COLD STRATI- fluctuating 26 C day/18 C night periods in which competitive foliage is FICATION, AND SOWING TEMPERATURE. temperatures had the most consistent scarce. In the 2005 experiment, an interac- germination, all exceeding 80% (Fig. The benefit of perigynia removal tion occurred between warm storage 3). Sowing temperature of 30 Cday/ on germination appears to be species duration and cold stratification dura- 14 C night resulted in low germina- specific. Japanese sedge (Carex kobo- tion (Table 2), which can be explained tion (Fig. 3). mugi), a coastal sand dune sedge, by the variable response to 1 and 2 A three-way interaction occurred required scarification of the achene months of warm storage (Fig. 3). during the 2006 experiment between in addition to perigynia removal Non-stratified achenes and 2-month storage, stratification, and sowing (Ishikawa et al., 1993). In contrast, 12 stratified achenes did not exhibit sig- temperature (Table 2) due to the in- North American wetland Carex spe- nificantly improved germination if consistent response of achenes that cies germinated to high percentages without perigynia removal or scarifica- tion (Kettenring and Galatowitsch, 2007a). This variability between closely related species within the ge- nus Carex is common (Kettenring and Galatowitsch, 2007a). No study has been conducted to determine why an intact perigynium may reduce achene germination; however, Jones et al. (2004) suggested that the peri- gynia may reduce the light reaching the achene. EXPT.2:STORAGE TEMPERATURE, DURATION, AND GA3. Presowing storage temperature and duration Fig. 2. The effect of storage temperature and storage duration on germination of affected germination, but GA3 pre- 2006 pennsylvania sedge achenes. Achenes were stored at 22 C for 5 weeks after treatment did not. Storage at 22 C harvest and then subjected to storage at 22 C (warm) or 4 C (cold) for an for 16 weeks increased germination additional 4, 8, or 16 weeks. Error bars represent SE. Mean values labeled with percentage in comparison with achenes different lowercase letters were significantly different according to Fisher’s stored at 4 C for either 4 or 8 weeks or protected least significant difference test at P £ 0.05 (n = 12 viable achenes, eight for achenes stored at 22 Cfor4weeks replications); (1.8 ·C) + 32 = F. (Fig. 2). (The number of storage weeks does not include the initial 5 weeks of Table 2. Summary of analysis of variance results for the effects of storage, cold warm storage after harvest.) It appears stratification duration, and sowing temperature on 2005 and 2006 pennsylvania that length of storage is more impor- sedge germination. tant than storage temperature for Significance pennsylvania sedge germination. Opti- mum storage conditions appear to be Source df 2005 2006 habitat specific. Wetland sedges benefit Storage 1 *** * from cold, wet storage (Budelsky and Stratification 2 * * Galatowitsch, 1999), while prairie Temperature 2 *** * (Larson and Stearns, 1990) and forest Storage · stratification 2 ** NS sedges respond to dry-warm storage Storage · temperature 2 NS NS (Schutz, 1997b). While pennsylvania Stratification · temperature 4 NS NS sedge benefited from an extended pe- Storage · stratification · temperature 4 NS * riod of dry storage under either cold or NS, *, **, ***Nonsignificant or significant at P £ 0.05, 0.01, or 0.001, respectively.

190 • April 2011 21(2) were stratified for 1 month. With the the 12 North American wetland species attributed to several factors. Schutz exception of one treatment, achenes studied across many different germina- and Rave (2003) reported a large that had been cold-stratified for 2 tion temperature regimes (Kettenring variation in germination between months exhibited the most consistent and Galatowitsch, 2007a). four populations of elongated sedge germination (Fig. 4). Germination In our experiments, the germi- that were only 15 km apart. Popula- was much lower for all treatments in nation percentage ranged from 57% tion differences may also explain our 2006 than in 2005. to 96% in 2005 and from 31% to 67% result. In the 2006 stratification ex- Cold stratification significantly in 2006. These variable results are periment, different achene sources increased germination in 28 of 32 consistent with previous studies of were necessary due to limited avail- European Carex species (Schutz and North American sedges (Kettenring ability. Thus, the variation in results Rave, 1999). Stratification also in- and Galatowitsch, 2007a, 2007b). between the 2 years may be genetic. creased the germination of most of The variation between years may be In addition, variation between the same populations may occur between consecutive years (Schutz and Rave, 2003). Different climatic conditions during ripening cannot be discounted. Achenes collected in 2006 appeared to have more smut infestation than those collected the previous year. Conclusions Our experiments outline several treatments that enhance pennsylva- nia sedge germination. After harvest, achenes should be warm-stored or after-ripened for an extended period. No loss of germination percentage was observed as after-ripening increased up to 21 weeks at 22 C. Eight weeks of cold stratification in conjunc- Fig. 3. The effect of warm storage duration, cold stratification, and sowing tion with after-ripening yielded more temperature on 2005 pennsylvania sedge achene germination. The black and consistent germination. Removal of gray columns depict 1 and 2 months of after-ripening, respectively, at 22 C. the perigynia before cold stratification Achenes were cold-stratified at 4 C for 0, 1, or 2 months. For each stratification and incubation in white light also period, data are presented for sowing temperatures of either constant 22 Cor enhanced germination. Using these fluctuating day and night temperatures of 26 C day/18 C night or 30 C day/14 treatments, we believe pennsylvania C night. Mean values labeled with different lowercase letters were significantly different according to Fisher’s protected least significant difference test at P £ 0.05 sedge can be effectively produced from (n = 25 viable achenes, eight replications); (1.8 ·C) + 32 = F. seed for restoration or horticultural purposes.

Literature cited Abrams, M.D. and D.I. Dickmann. 1984. Floristic composition before and after prescribed fire on a jack pine clear-cut site in northern lower Michigan. Can. J. For. Res. 14(5):746–749. Amen, R.D. and E.K. Bonde. 1964. Dor- mancy and germination in alpine Carex from the Colorado front range. Ecology 45(4):881–884. Baskin,C.C.andJ.M.Baskin.1998. Seeds: Ecology, biogeography, and evo- lution of dormancy and germination. Academic Press, San Diego, CA. Fig. 4. The effect of warm storage duration, cold stratification, and sowing temperature on 2006 pennsylvania sedge achene germination. The black and Baskin, C.C. and J.M. Baskin. 2004. De- gray columns depict 1 and 2 months of after-ripening, respectively, at 22 C. termining dormancy-breaking and germi- Achenes were cold-stratified at 4 C for 0, 1, or 2 months. For each stratification nation requirements from the fewest period, data are presented for sowing temperatures of either constant 22 Cor seeds, p. 162–179. In: E.O. Guerrant, fluctuating day and night temperatures of 26 C day/18 C night or 30 C day/14 K. Havens, and M. Maunder (eds.). Ex C night. Mean values labeled with different lowercase letters were significantly situ plant conservation: Supporting spe- different according to Fisher’s protected least significant difference test at P £ 0.05 cies survival in the wild. Island Press, (n = 12 viable achenes, eight replications); (1.8 ·C) + 32 = F. Washington, DC.

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