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Daylength Controls Flowering of Tuberous-Rooted Begonias

Charles A. Lewis

Dept. of Floriculture and Ornamental HorticultureCornell University, Ithaca, N. Y.

Tuberous-Rooted Begonia flowers areworth twice as much during the winter as insummer. In the past, production has been onlyduring the spring and summer, but now you canhave these plants in bloom any day of theyear. For the past ten years in California,the flowers have been used commercially inall types of make-up work. They are so popular that one large retail shop in San Francisco uses 50,000 blooms during the springand summer.

The plants grow best and the flowersare largest at night temperatures of 55-60°F. In the Eastern United States thesetemperatures can be maintained only duringthe winter months. Therefore, Tuberous-Rooted Begonias would be at their best during the winter, but the plants normally godormant in the fall. These investigationswere made to determine what environmental

factors control the growth and floweringof these plants.

They Bloom Under Long Days

In November, 19^9* cuttings were takenof several Camelliaflora varieties and the

Multiflora variety, Bourgemeister Max.These were rooted in sand with 70° bottomheat. The rooted cuttings were pottedand grown under long and short day conditions. Plants given long days were provided

with artificial light from Mazda bulbs tosupplement the normal daylength. The supplementary light was given from 4 p.m. to2 a.m. The short days were provided by normal winter light conditions, which at Ithacavary from 10 hours of light on December 16to 12 hours of light on March 1. A thirdgroup of rooted cuttings were grown forthirty (30) short days and then given thirty(30) long days.

The plants continued to grow andflower under long days; but under short daysthey stopped growing, the leaves becomingthick and dark green, and produced noflowers. Plants that had stopped growingunder short days started to grow and floweragain when placed under long days.

The plants under short days formedtubers while the plants under long daysdid not form tubers. A few of the Multifloraplants not only formed tubers under the soilduring short days but also formed tubers ontop of the plant.

This experiment shows that Tuberous-Rooted Begonias grow and bloom under longday conditions, 18 hours in this case, andcease growth and form tubers under shortdays.

Continued on next page.

Daylength treatments left to right; 9, 10, 11, 12, 14, 16 hours of light and interrupteddark. Light periods of 9 through 12 hours not effective in causing growth and flowering. 14, 16 hours of light and interrupted dark results in growth and flowering.

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During the summer of 1950 a study wasmade to determine the effect of high temperature on the daylength response. Multifloraand camelliaflora plants were grown underboth longand short

days. Againthe plantsunder longdays grewand bloomed

but did not

form tubers.

The plantsunder short

days stoppedgrowing andformed

tubers. It

is evident

that highsummer tem

peraturesdid not af

fect the

daylengthresponse.

the soil but also at the ends of the stems.The aerial tubers had been observed in theprevious year's experiment. Ami Jean Bardformed these tubers more often than did Helen

Harms. No

aerial tubers

were formed on

the camellia-

flora types.

the*

ments it Is

obvious thatTuberous-Rooted

Begonias may bebrought intoflower any dayof the year!

Timing theProduction

The plantsmay be propagated from seeds,tubers, and cuttings. Seedsrequire approximately six monthsfrom sowing to

the first bloom. The tubers and cuttingstake about three or four months to produce blooming plants. At present we are trying to determine exactly how long a period isrequired from cutting to 4-inch pot and fromtuber to 4-inch pot. This information willbe published in this Bulletin as soon as itis available. The cuttings used are t*p cuttings which will root in a month in Vermicu-lite. A more vigorous plant is obtained morequickly by this method than from tubers.

Difficulty has been experienced in thepast in having these plants in bloom forEaster. The trouble arises from the factthat when the tubers are started the daysare short and growth is slow. Actually, hereat Ithaca, the days don't reach 14 hours tillApril. So, if early plants are desired, itwould be best to give the sprouting tuberslong days as soon as the first shoots appear.

Whenever off-season production of theseplants is desired, the daylength must be atleast 14 hours. Short days for Tuberous-Rooted Begonias occur at Ithaca from September 1 to April 8, and any plants grown duringthis period would have to be given additionaldaylength. Probably four (4) hours of additional light applied in the middle of thenight would be sufficient.

Future Possibilities

The pot plant possibilities of theTuberous-Rooted Begonia have as yet beenlargely uninvestigated. The multiflora group,which is relatively unknown in the UnitedStates, is similar in size to the ChristmasBegonia. The plants are about l-l£ feet tallwith many branches from the base, each branchbearing many small flowers. The varietyBourgemeister Max is a deep red that would be

Continued on Page 8

From

;e experi-

To de

termine the

minimum daylength for flowering, camelliaflora plantswhich had been started from seed in March1950, and rooted cuttings of Multifloravarieties, Helen Harms and Ami Jean Bard,were used. Artificial light to supplementthe normal daylight was used to provide 9,10, 11, 12, 14, and 16 hour days. One additional treatment consisted of an Interrupteddark period, which was provided by giving 9hours of normal daylight followed by 4 hoursof dark, l£ hours of light, 4 hours of dark,1-^ hours of light, and 4 hours of dark tocomplete the 2?-hour cycle. The plants werefrown at a minimum night temperature of0°F. The supplementary light source wasfrom 60-watt Mazda bulbs placed about 2\ feetabove the plants and 4 feet apart giving alight Intensity of 6 to 25-foot candles.The supplementary light was given in themorning and the evening to extend the lightperiod at both ends of the day. An automatictime clock controlled the length of day ofeach treatment.

The camelliafloras stopped growing andflowering when the light period was 12 hoursor less, and the leaves became dark greenand the stems hardened. When the daylengthwas 14 or 16 hours, or when the dark periodwas interrupted, the plants continued to growand bloom. The interrupted dark period provided a total of 12 hours of light but theplants in this treatment gave the same response as those given 14 or 16 hour days.The multlfloras under the 12 hour days produced some growth. Plants under the 14 and16 hours of light and the interrupted darktreatment produced normal healthy growth andflowered.

Tuberization occurred only on the plantsin the 9, 10, 11, and 12 hour light cycles.Some of the plants not only formed tubers in

AERIAL TUBER FORMATION ON AMI JEAN BARD GROWN IN SHORT DAY

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Papers Reviewed

Forcing Tests with Georgia Lily.

Stuart, Nell, W. Florists' Exchange 115(15). 1950.

Georgia lilies require slightly longertime for flowering than Creoles. ProducedIn Southeastern United States, they forceeasily for mid-winter and Easter markets.Georgia lilies produce more flowers thanCreole or Crofts from the same sized bulb.

Moist storage of bulbs at 45°F for 6 weeksbefore planting gave earliest flowering.Storage in moist packing material at 32°For slightly below is preferred for latebloom.

Photoperiodic Responses ofPolnsettia.

Parker, M. W., H. A. Borthwickand Laura E. Rappleye. Florists'Exchange 115(20): 11, 49-50; 1950.

Plants were in full bloom 65 to 75days after the beginning of short days.Day lengths of 8 or 9 hours were aboutequally effective In causing flowering.Flowering was slightly delayed with 11 hourdays and much delayed with 12 hour days.Late cuttings did not respond Immediatelyto short days. Flowering is prevented if30-foot candle minutes (3 minutes of 10-foot candles) of light is given near themiddle"of the dark period. More uniformflowering might result if plants are givenadditional light to October 1 then givenartificial short days of 8 or 9 hours.

Editor's Note: Short days started October1 would produce plants in full bloom byDecember 5 to 15 according to the author'swork. Normal date for bud initiation is

October 10 to 20. If the suggested treatment is applied, best flowering for Christmas would consist of lengthening the dayfrom October 1 to 15, then reducing it for15 days.

Control of Fusarlum Storage Rotof Gladiolus CormsT

Miller, H. N. and R. 0. Magie.Phytopath 40(2): 209-212. 1950.

Heavy corm losses from Fusarium rot insusceptible gladiolus varieties occur duringstorage. This disease can be controlled bytreating the corms with a fungicide at thetime they are cleaned. Spergon used as a 2per cent dip or a 50 per cent dust, and adip of Fermate 0.5 per cent plus Dow 9B0.375 per cent were the most effective treatments in controlling the rot.—BiologicalAbstracts.

Continued from Page 3

particularly appropriate for Christmas.Helen Harms is a lemon yellow that shouldmeet with favor at Easter. The multiflorasare hardier than the larger flowered typesand would hold up better in the customer'shome.

Left to right; Interrupted dark and 9 hourslight daily. Growth and no tuberizationoccurred under interrupted dark while topsdid not grow but tubers formed under 9 hourdays.

The large camelliaflora types would haveto be handled carefully if used as a potplant. It would be best to grow the plantsto three or four stems so that the flowerswouldn't be too large. Shipping a plantwith large flowers would be hazardous. Itshould be remembered that the Tuberous-RootedBegonia as a pot plant has a double appealin that after the customer has grown theplant in the home he may plant it outsidein the garden for a continued summer bloom.

As a pot plant and a cut flower, theTuberous-Rooted Begonia has a future. Nowthat they can be flowered any day of theyear the commercial production of theseplants Is entirely practical.

• Next month's Bulletin will feature othertalks given at the Cornell Short Course, January 17 and 18, 1951.

Your Editor,

^^t^&tr^^r