Effects of Runner Tip Sizeand Plugging Date on Fall Flowering

in Short-Day Strawberry(Fraga ria X ananassa Duch.) Cultivars

Furniorni TakedaMichael Newell

ABSTRACT. Producing strawberry transplants Irorn runner tips [hatwere plugged -I month earlier (early July) than the standard time (earlyAugust) promoted rail flowering in some short-day strawberry culiivars.In 2002. IOWl or 'Chandler' transplants produced in early July floweredin the rail. but none or the August-plugged 'Chandler' transplants flow-ered in the rail. ln 2003. 73'X or 'Chandler' transplants produced inmid-July from average-size runner tips and less than hall' or transplantsIrorn small-size runner tips flowered in the rail. Again, August-pluggedplants did not flower in the rail. Flowering was absent in 'Northeaster'plants. Uncler protected cultivation. July-plugged 'Sweet Charlie' plantsbloomed earlier and produced more fruit in November and December[han those plugged in August. This study showed that raIl floweringin 'Chandler' and 'Sweet Charlie' strawberry is possible i I' the trans-plants arc prepared by plugging runner tips in early July. This noveltechnique for propagating strawberry transplants for annual plasticulturc

Fumiorni Takeda is Research Horticulturist and Lead Scientist tor Small Fruit Pro-duction Systems. Appalachian Fruit Research Station. United States Department orAgriculture. Agricultural Research Service. 2217 Wi Itshire Road. Kearneysville. WV25 ...f:jO.

Michael Newell is Horticultural Crops Manager, University or Maryland. WyeResearch and Education Center. PO Box 169. Queenstown. MD 21658.

International Journal or Fruit Science. Vol. 6('+) 2006Alai lable onl inc at http://ijfs.haworthpress.colll

<D2006 by The Haworth Press. Inc. All rights reserved.dod O. 1300/J'+9.2v06nO'+_1 0 103

104 INTERNATIONAL JOURNAL OF FRUIT SCIENCE

combined with production under high tunnels creates an opportunity Iorstrawberry production in early winter and again in the spring (doublecropping) in the mid-Atlantic coast region. doi: 10. I300/J4lJ2v06n04_1 0/A rticl« COllies availablejor afeefrom Tile Haworth Document Deliver. Service:1-800-1-IAWORTH. Enuail address: <docdelil'('JT(jj'II{/1l'{}rlllllresl.colll> svcbsit«:<1I"ld/\l·ll'\l'.l-!u\\'oI'lIlPress.col//> Q 2006 bv Tile Haworth Press, lnc. All right»reservcd.]

KEYWORDS. High tunnel, greenhouse, propagation. flower initiation,yield, season extension

INTRODUCTION

The main strawberry harvest season in the mid-Atlantic coast regionCwoN, nOW) is from early May to late June. Out-of-season fruit pro-duction in the region is very limited. Fruit of the day-neutral 'Seascape'harvested in November and December have been direct-marketed atUS$3.00-4.00 per pound or about four times higher than fruit harvestedin spring to restaurants in the Metropolitan Washington-Baltimore area(Takeda, unpublished), As a result interest in out-of-season strawberryproduction systems has increased in the mid-Atlantic coast region(Durner, 1999; Takeda, 1999; Takeda et al., 2004, 2006; and Takedaand Hokanson, 2002, 20m). Containerized nursery (plug) plants andthe annual plasticulture system has allowed several cultivars devel-oped elsewhere (e.g., 'Chandler', 'Marrnalada", 'Seascape' and 'SweetCharlie') to be grown in the region. Planting of these cultivars using theplasticulture system has provided opportunities to extend the harvestseason in the spring and make fruit harvesting more efficient in areaswith prevailing mild winter climates (e.g., eastern North Carolina andVirginia). Short-day strawberry plants that will flower in the fall orshortly after planting in late August or early September would be desirablefor the region, Innovative production technologies such as plasticulture,floating rowcovers, and high tunnels for environmental modificationsare already available for extending the harvest season well into lateDecember in the mid-Atlantic coast region (Fernandez and Bullington,2003). Short-term cropping systems improve opportunities for farmdiversification and help growers to produce a variety of fruit and vege-table crops for niche markets. Income from fall and spring fruit produc-tion (double cropping) can raise farm profitability.

Funtionii Taked« and Miclut«! Newell 105

Flower buds initiation in short-day strawberry cultivars starts in theshorter days of late summer to early spring whenever the temperaturesare high enough (Darrow, 1966). Darrow (1966) noted that althoughshort-day strawberry plants developed in the mid-Atlantic coast regioncan differentiate flower buds in the fall, anthesis does not occur in themin the fall because of less than ideal temperatures for reproductive de-velopment. Recently, Bodson and Verhoeven (2005) observed in thecv. 'Elsanta' that the first sign of inflorescence initiation started in Oc-tober and carpel primordia initiated in November but they observed nofurther differentiation in the winter.

The physiological state of plug transplants and nursery conditions inwhich transplants are produced affect whether flower induction and in-florescence differentiation occur during the propagation phase or shortlyafter field establishment. Sonsteby and Hytonen (2005) and Verheul et al.(2006) reported that flower emergence and development in 'Korona' canbe controlled by udj usti ng photoperiod, temperature, the duration ofshort-day treatment and plant age under greenhouse conditions. Fernandezand Bullington (2003) produced a moderate crop (175 g per plant) in thefall with conditioned 'Sweet Charlie' plants in the coastal region ofNorth Carolina (USDA Hardiness Zone 7a). Their conditioning regimeinvolved production of runner tips and transplants at a high elevation(-900 m above sea level) nursery in western North Carolina and3 weeks of artificial short-day treatment. Durner (1999) reported thatfruit production increased -80 g per plant in January and February when'Sweet Charlie' strawberry plug plants, 2-3 weeks old, were exposed inSeptember to seven 9-h days without chilling (21°C day/21°C night, fol-lowed by seven 9-hour short days with chilling during the dark period(12°C night). In Japan, a technique described as an "extra early forcingculture" of cool night (13-14°C) and short-day ( 16-h dark) treatmentsfor -20 days or holding transplants at IT'C in the dark for 14 days in latesummer is used to accelerate fall flowering (Oda, 1992). These treat-ments involve laborious daily movement of transplants in- and-out ofcold rooms or dark rooms or the drawing of a black drop cloth over theplants for up to 3 weeks. The constraint to getting these preconditioningtechnique widely accepted has been the high production cost coupledwith low productivity (Sonsteby et al., 2006). In Maryland, Takeda andNewell (2006) reported that fall flowering occurred in plants of theshort-day 'Carmine' strawberry by simply advancing the plugging dateof runner tips to early July for producing transplants used in annualplasticulture.

106 INTERNATIONAL JOURNAL OF FRUIT SCIENCE

The objectives of this study were to determine the effect of tip sizeand plugging date of 'Chandler' and 'Northeaster' strawberry trans-plants on fall flowering and spring yield in an outdoor plasticulture sys-tem and the effect of plugging date and planting date of 'Sweet Charlie'transplants on early winter and spring fruit production in a high tunnel.

MATERIALS AND METHODS

Strawberry Cultivars

In 2002 and 2003, we used 'Chandler' strawberry, a 1983 Universityof California release (Voth and Bringhurst, 1984). 'Chandler' straw-berry is the most widely used cultivar in the annual eastern productionsystem outside Florida (Poling, 1993). In 2004, we evaluated 'SweetCharlie' and 'Northeaster' strawberry. 'Sweet Charlie' strawberry is ashort-day cultivar from the University of Florida (Chandler et al., 1997)that tends to produce fruit early (C.K. Chandler. University of Florida,personal communication). 'Northeaster' strawberry, a 1994 USDA re-lease (Galletta et al., 1995), is an early-season cultivar developed for thetraditional matted row production system. The source of plants for run-ner production and runner tips for plug plants, plugging dates, fieldplanting dates and data collected in fall and spring are summarized inTable I. Details of propagation methods and greenhouse growing con-ditions are provided elsewhere (Bish et al., 200 I; Takeda and Hokanson,2002,2003; Takeda and Newell, 2006; Takeda et al., 2004, 2006).

In 2004, Davon Crest Farm, Hurlock, MD, provided runner tips of'Sweet Charlie' strawberry on July I, August 3 and 17. Tips were pluggedinto SO-cell packs containing Sunshine LC I mix. The plug plants weremist sprinkled for 2 weeks in a greenhouse at the University of MarylandWye Research and Education Center (WREC), Queenstown, MD, afterwhich they were set outside the greenhouse until they were planted inraised beds prepared under a high tunnel in September (Table I).

Field Production System

In all 3 years, strawberry transplants were established in the plasti-culture system (Poling, 1993) at WREC. Information regarding theplanting site and pre-plant preparation are given elsewhere (Takeda andNewell, 2006). Strawberry transplants were established in plasticulturesystem at WREC on September lOin 2002, September 8 in 2003 and

Funiionii Takeda and Michael Newell 107

TABLE 1. Runner tip source, cultivars tested, plugging and planting date,and field data collected in fall and spring for 2002-2003, 2003-2004, and2004-2005 studies.

Source of plants Cultivar Plugging and Fall data Spring dataplanting dates

2002-2003 study: 'Chandler' July 2 and Plant survival Total yieldCommercial September 10 Branch crown Fruit sizenursery, August 8 and Runner number Branch crownHurlock, MD September 10 Percentage of number

plants withflowers

2003-2004 study 'Chandler' July 17 and Plant survival Total yieldUniversity of September 8 Crown number Fruit sizeMaryland: College August 13 and Runner number Branch crownPark, MD and September 8 Percentage of numberSalisbury, MD plants with

flowers

2004-2005 study: 'Northeaster' July 3 and Crown number Marketable yieldUSDA-ARS September 1 Runner numberKearneysville, WV August 5-6 and Percentage of

September 1 plants with

Commercial 'Sweet July 1 and flowers Marketable yieldMarketablenursery, Hurlock Charlie' September 13yieldMD August 3 and

September 13August 17 andSeptember 21

September I in 1004. Planting dates approximated the recommendedtransplanting for this region. The plants were arranged in offset doublerow spaced 30 ern between and in rows with IO-plant plots. Plots wererandomized in a complete block design with four replications for eachcultivar/rreatrnent. Plots were irrigated by overhead micro-sprinklersfor 1 days during establishment.

High Tunnel Production

For high tunnel production studies in 2004, we used a 19.5-m long x 9.I-mwide high tunnel (Ledgewood Farm Greenhouse Frames, Moultonboro,NH), constructed in 2003 at WREC. Plants and plastic mulch from the2003-2004 production cycle were pulled out on July 16, 2004, and theground was rota-tilled deeply. Fertilizer (16-8-8) was incorporated into

108 INTERNA T10NAL JOURNAL OF FRUIT SCIENCE

soil by shallow tillage at the rate of 450 kg-ha :". Crowned beds (10 ernhigh and43 cm wide) were formed with a bed shaper at 1.25 m spacingbetween row middles, a drip irrigation tube with discharge rate of 1.7l·min--I·(30.S m)-I was placed off-center on each bed. Beds were cov-ered with black polyethylene mulch. Strawberry transplants were hand-planted in the middle of each raised bed at 30-cm intervals. On September13, 2004, 'S weet Chari ie' transplants that were started on July I andAugust 3 were set in the ground. On September 21, transplants startedon August 17 were set in the ground. Twenty transplants were set in eachplot. Plots were irrigated with micro-sprinklers for 2 days. Transplantsreceived a post-transplant application of starter fertilizer (20-20-20) atI kg·(380 I)-I water. Fungicides. insecticide and drip irrigation wereapplied as needed. There were four replications consisting of a combi-nation of plugging and planting dates.

Field Performance Data Collection

In 2002, the following data were collected on November 14 in eachplot: number of surviving plants, number of plants with flowers andfruit, and runner and branch crown number (only for three plants perplot). Runners, flowers and fruit were discarded. In fall 2003, runner.crown, and flower/fruit development was determined on December 10as previously detailed for year 2002, except runner and branch crownnumbers were recorded for all 10 plants in the plot. In fall 2004, data onrunner and branch crown number for each plant and number of plantswith flowers and fruit in each plot were recorded on November 3 afterwhich all runners were detached by hand. On November 18, we de-tached and counted flower buds, flowers, and green and red fruit, andweighed large fruit.

'Sweet Charlie' strawberry plants grown in a high tunnel were har-vested on November 12 and24, and December 7 and 21, 2004. At eachharvest, data were collected for plot yield and number of fruit harvested.

In spring 2003, 2004 and 2005, we harvested ripe strawberriestwice weekly from mid-May to mid-June in field plots. In spring 2005,plots of 'Sweet Charlie' strawberry inside the tunnel were harvestedtwice weekly from late March to June. Each fruit was graded as mar-ketable or cull, and weighed. Individual plant yield for the season wascalculated.

Ftnuiotni litkei/o (/1/(1 Micllllel Nell'ell 109"0CeuC\JooC\J

Statistical Analysis

Analysis of variance (ANOY A) for treatment and cultivar was carriedout using PROC GLM of SAS (200 I). Calculated percentage values werearcsin transformed prior to imposing statistical analysis. Means separa-tions were determined using the DIFF option for all contrast (P ::; 0.05).

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RESULTS

2002-2003 and 2003-2004 Studies

cPost-establishment plant loss was minimal in 2002 and 2003 (Table 2).All the July-plugged 'Chandler' transplants had produced flowers bymid-November while none of the August-plugged transplants had (Table1). Branch crown development was greater in the early July-plugged trans-plants than in the early August-plugged transplants, 1.3 versus 1.2 perplant, respectively. Runner production was rather low in all treatments. Inthe 10m study, 7Y7c of the July-plugged transplants had flowered byNovember, hut fall bloom was not observed in the August-pluggedtransplants (Table 1). None of the transplants obtained from a commer-cial nursery flowered in the fall (data not presented). Since the plantswere in the open culture system, fruit were injured by frost and nonereached the stage for harvesting in fall of 2002 and 20m. The pluggingdate of July 17 for 2003 season was 2 weeks later than in the previousyear. The delay in plugging may have been a factor in that only 73% ofthe July-plugged 'Chandler' plants producing flowers in the fall.

In spring 1003, fruit was harvested for 4 weeks. Yield per plant was704 g for the July-plugged transplants and-560 g for the August-pluggedtransplants (P = 0.081). These yields are equivalent to -19.6 and 23.5metric t ha-I based on the -41,000 transplants ha : I planting densityand are far better than those reported for annual plasticulture studiesconducted in New Jersey (Fiola et al., 1995), and slightly higher thanthose obtained in commercial fields in North Carolina (Poling, 1993). Totalmarketable yields obtained in our 1003-1004 study were -15 metrict ha -I across treatments. The tonnage approached those yields obtainedfrom 'Chandler' plants in a field study conducted near Raleigh, NC(USDA Plant Hardiness Zone 7b) during 1986-1987 season (Poling,1993). Average fruit size for the season was similar with 23 and 24 g perfruit for the July- and August-plugged treatments, respectively. By theend of the harvest period in June, July-plugged plants possessed one

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more branch crown than those plugged in August (P = O.OOS). In 2004,fruit was harvested for 2 weeks from May 10 to May 25. Yield per plantwas between 600 and 650 g, average fruit weight was -18 g and branchcrown numbers averaged about five on each plant across the treatments(not significantly different at P = 0.05; Table 2).

None of the 'Northeaster' plants flowered in the fall (Table 3). In thefield, runner production was less than two per plant in 'Northeaster'plants (Table 3). These runner numbers were lower than in a previousstudy in which five runners were produced on the July-plugged 'North-easter' transplants that were established in plasticulture on August 12 atBeltsville, MD (Hokanson et al., 2004). These results agree with find-ings of Poling ( 1993) that containerized strawberry plants establ ished inthe annual plasticulture system in mid-to-late summer (August) tend toproduce more runners in fall than those established in early fall (Sep-tember). In spring 2005, 'Northeaster' was harvested from May 12 toJune 7 totaling eight pickings. There was no effect of runner tip size onspring marketable yield or fruit size (average fruit weight of 17 g acrossall treatments). The lowest marketable yield (646 g per plant) was notedin plants propagated in August from small tips (Table 3).

In the high tunnel study, we harvested fruit from 'Sweet Charlie'strawberry in November and December and again starting in late March

for -13 weeks. The plants that were plugged in early July and estab-lished in mid-September produced twice as much fruit in November andDecember as did August-plugged plants that were established in mid- orlate September (Table 4). Planting date closer to September I or even inlate August may provide greater yields in the fall in colder climatic areas(USDA Plant Hardiness Zones 7'1 and 6b) (Fiola et al., 1995; O'Dell andWilliams, 2000). In the spring, July-plugged plants produced signifi-cantly more fruit than plants plugged in August (Table 4).

2004-2005 Study

DISCUSSION

TABLE 3. The effect of plugging date and runner tip size of 'Northeaster' straw-berry on fall branch crown, runner production and flowering, and fruit produc-tion in spring. *

There is an optimal planting date for each cultivar recommended forthe plasticulture in the region (Fiola et al., 1995: O'Dell and Williams,2000). Transplants that are field planted late produce less fruit in spring(Fiola et al., 1995; O'Dell and Williams, 2000: Takeda and Hokanson,2002). Takeda and Newell (2006) suggested that spring yield was re-lated to branch crown development in the fall. Earlier planting datesprovide more days in the fall for plant growth. However, if plantingsoccur too early then plants may grow excessively and more runners mayappear in the fall (Poling, 1993). In our study, the growing conditionsunder the high tunnel in December appeared to be satisfactory for plantgrowth since 'Sweet Charlie' plants were still producing flowers in lateDecember.

Other researchers have described 'conditioning' treatments for plugplants such as exposure to specific high and low temperatures (Bish et al.,

Plugging date Tip size Fall branch Fall runners Plants with Spring cropcrown production inflorescences (g/plant)

development (no./plant) in fall (%)(no./plant)

Early July Average 3.8a2 1.2b Oa 873aSmall 3.3b 1.1b Oa 781a

Early August Average 2.5c 2.2a Oa 699aSmall 1.8d 1.3b Oa 646a

TABLE 4. Effects of transplant preparation method on fruit production duringNovember and December 2004 and spring 2005 in 'Sweet Charlie' strawberryplants in a high tunnel at the Wye Research and Education Center, Queens-town, MD.

•All transplants were established on September 2,2004 in outdoor plasticulture at the Wye Researchand Extension Center. Queenstown, MD (fall growth measurements were collected on November3,2004).zValues in columns followed by the same letters are not significantly different (P ~ 0.05). Meanseparation performed by DIFF option of SAS Proc.

Treatment Planting date Early winter marketable Spring cropplugging time yield (g/plant) (g/plant)

November DecemberEarly (July 1) September 13 21a2 35a 482aStandard (August 3) September 13 2b 18b 307bLate (August 17) September 21 Ob 20b 218b

zValues in columns followed by the same letters are not significantly different (P= 0.05). Mean separationperformed by DIFF opfion of SAS Proc. Mixed.

Futnionii Takeda and Michae! Newetl J/3 1/4 INTERNA TlONAL JOURNAL OF FRUIT SCIENCE

2004), low temperatures and short-day photoperiod (OLII'ner, 1999;Heide, 1977; Hytonen et al., 2004; ada, 1992; Verheul et al., 2006) toforce short-day strawberry transplants to flower shortly after establish-ment in out-of-season production systems. The earliest tlowering thatVerheul et al. (2006) observed in an 8-week-old "Korona' transplantwas at -48 days after completion of the treatment. The difference in thenumber of days to flowering clearly demonstrates that the sensitivity ofthe strawberry plants to photoperiod and/or temperature and varies withcultivar, plant material, and their age. We have developed a simple pro-tocol that does not need cold temperature exposure or photoperiodicmodifications to force short-day cultivars to tlower under outdoor con-ditions in the fall in Maryland. Fall flowering occurred in high percent-age of transplants from runner tips harvested and plugged in early July,maintained in the greenhouse for -8 weeks, and then field planted inearly September. Using this cropping system, we found that 'Chandler'and 'Sweet Charlie' strawberry would flower shortly after field estab-lishment and produced ripe fruit as soon as 2 months after planting.

The critical components for producing strawberries in the fall in themid-Atlantic coast region with short-day cultivars are as follows: (I) useof cultivars developed primarily for areas with mild winter climates,(2) preparation of containerized transplants in early July, (3) field estab-lishment of transplants around September I or slightly earlier, and(4) season extension with protected cultivation techniques. Even withearly July-plugged transplants, if field planting occurs in mid-Septemberor later, the prospect of harvesting ripe fruit in November and Decemberis significantly reduced (Table 4). Fall fruit production was negligiblein 'Chandler' plants that were started from runner tips harvested in earlyJuly, cold-stored for 4 weeks at 2°C, plugged into cell packs in earlyAugust, and field transplanted in early September or from -4-week-old"Chandler' transplants obtained from a local strawberry transplant pro-ducer (Takeda et al., 2006). Our findings suggest that fall fruit productionis unlikely from transplants produced by the conventional strawberryplug transplanting technology, for example, transplanting plug plants,that were 3.5-5 weeks old, produce in 48- or SO-cell packs in earlySeptember. In addition, it was not possible for the short-day cv. 'North-easter' that was developed for areas with severe winter climates toflower in the fall. Fall environmental conditions in the mid-Atlanticcoast region are not adequate for promoting tlower bud formation or out-of-season bloom in northern cultivars or those developed for areas withcold winters (Darrow, 1966). For example, in winter fruit productionstudies conducted in a heated greenhouse with supplemental lighting

(Takeda et al., 1999), the earl iest harvest occurred in February forfall-established 'Primetime' and 'Delmarve!'. two cultivars released byUSDA-Beltsville, MD, but as early as December for the short-day cv.'Camarosa' that was developed in California with mild winter climates.

The origin or source of plants for generating plug plants, growingconditions for plug transplants, and field establishment date used in thisstudy varied from year to year, but the results of our studies clearlyshowed that at least for 'Sweet Charlie' and 'Chandler' strawberries thetime of runner tip harvest and plugging had a profound effect on fallflower production. This modification in plug-plant production tech-nique for producing transplants offers opportunities for strawberrygrowers in the mid-South, mid-Atlantic coast regions and other areaswith cool full climates to double-crop short-day strawberry cultivars inlate fall and in spring. Transplants of short-day cultivars 'Chandler'(Table 2), 'Sweet Charlie' (Table 4) and 'Carmine' (Takeda and New-ell, 2006) strawberries that were propagated in early July and estab-lished in the field in early September respond to natural photoperiodicinduction (long nights) for reproductive development. At the test site inQueenstown, MO (latitude 39°N), daily dark period increases to > 10hours around September I. Temperatures in September and October aregenerally sufficient for July-propagated plants to complete floral buddifferentiation shortly after field establishment and subsequently floweraround October I and produce harvestable fruit by early November.

CONCLUSIONS

Our studies demonstrated that fall flowering in "Chandler' and 'SweetCharlie' strawberry is inducible by advancing the plugging date to earlyJuly. As Bish et al. (2004), Fernandez and Bullington (2003) andVerheul et al. (2006) showed, short-day cultivars can be induced toflower early by growing transplants in artificial, short-day and cooltemperature conditions in late summer. However, the cost of the equip-ment and the energy needed to condition transplants by these methodsfor floral induction are high. Our method for promoting fall flowering insome short-day cultivars appears to be more practical and does not re-quire artificial lighting or cooling. Transplants produced by this methodare -8-weeks-old by the time they are established in the field. Commer-cial plug-plant propagators prefer to deliver -4-week-old transplants togrowers (D. Lankford, Hurlock, MO, personal communication). Anearlier tip harvesting time and additional time in the nursery would cer-

Funiiomi Takeda alit! Michael Newell //5 //6 INTERNATIONAL JOURNAL OF FRUIT SCIENCE

tainly increase cost of producing transplants, but this new planting ma-terial allows growers in the mid-Atlantic coast region to double-cropshort-day strawberries in high tunnels.

The potential strawberry yield in the fall and early winter under pro-tected cultivation can increase income. There are several methods to ob-tain fall fruit production in the mid-Atlantic coast region. Dormantday-neutral 'Seascape' strawberries planted in late spring and de-flow-ered for ? months produce some fruit as early as September (1'. Nourse,South Deerfield, MA, personal communication). Cold-stored waitingbed plants and module or tray plants are used in Europe for autumncropping on substrate culture (Lieten et al., 2005). In our study, the trans-plants plugged early in July grew in the greenhouse until the first weekin September under environmental conditions generally considered notfavorable for tloral induction (e.g., long days and temperatures> 21°Cduring day and night). However, they began flowering in -40 days afterplanting in the field under natural short-days and chilling temperaturesat night. It is possible to grow tray transplants after they are rooted out-side the greenhouse until field establishment as we have shown with'Sweet Charlie' transplants in the 2004-2005 study and still have trans-plants that will (lower in October and November. Our studies also con-firmed as others (e.g .. Fernandez and Balli ngton, 2003) have shown thathigh tunnels are useful for extending the production season. 'SweetCharlie' strawberry under a tunnel produced a small crop in Novemberand December and the main spring crop starting ill late March for -12weeks. In contrast, 'Sweet Charlie' plants in outdoor plasticulturedid not have harvestublc fruit until early May and harvest ran for onlyseveral weeks. We will determine whether transplants of other short-day cultivars (e.g., cvs. 'Camarosa', 'Darselect", 'Raritan' and 'Ventana)can be induced to flower in fall by advancing the time of propagation toearly July. The goal is to increase our understanding of the physiologi-cal control of flowering and create environmental conditions for im-proving the cropping potential of short-day strawberry cultivars in falland out-of-season.

LITERA TURE CITED

Bish. E.B .. D..I. Carnlitfc, and e.K. Chandler. 200 ..+' Strawberry transplant condition-ing for flowering induction. U.S. Patent 6.S07.760. October 26.

Bodson. M. and B. Verhoeven. 2005. Characteristics of dormancy of June-hearingstrawberry tFragaria x auuuassa Duch. cv, Elsanta). Int l. 1 Fruit Sci. 5:51-5S.

Chandler. e.K .. E.E. Albrcgts, e.M. Howard. and J.K. Brecht. 10l)7. 'Sweet Charlie'strawberry, HortScience l2: Ill2-II.B.

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