18 



The Florists' Review 



May 5, 1921 



only are there fewer hours of sunshine 

 per day, but the intensity of the light 

 also is reduced. There also is a dif- 

 ference in quality of light, since the 

 position of the sun during the winter 

 months is lower and, consequently, the 

 sun's rays must pass through a deeper 

 layer of atmosphere. 



Important Factors. 



Experiments were made to determine 

 the effects of these various factors on 

 flower production, and to find out what 

 it is that determines the time when a 

 plant will come into bloom. The fol- 

 lowing factors were studied carefully 

 in this respect: Soil fertility, tempera- 

 ture, soil moisture, and light. All these 

 factors were kept rigidly under control 

 during the course of the experiments 

 and only the one under consideration 

 was varied in each experiment. 



There is a rather common notion that 

 partial starvation of a plant will induce 

 flower development. Statements are 

 frequently made that a fertile soil stim- 

 ulates vegetative growth, while in a 

 poor soil the tendency is to produce 

 more flowers. In order to test this, to- 

 bacco plants were grown in pots or soils 

 of different nutritive conditions and 

 under partial starvation and it was 

 found that during the winter months in 

 the greenhouse "the plants invariably 

 blossomed without regard to the size of 

 the pot containing the plant or the ex- 

 tent to which the plant was stunted by 

 unfavorable nutrition conditions. ' ' This 

 conclusion refers only to time of flow- 

 ering; a more detailed discussion of 

 the relation between soil fertility and 

 flower production will appear in a later 

 article. 



Temperature and Soil Moisture. 



It was readily enough determined also 

 that temperature was not the deciding 

 factor of the blooming period. For in 

 growing the plants in the greenhouse, 

 the temperature of which was kept 

 quite as high as prevails outdoors dur- 

 ing the summer, the period of blossom- 

 ing was not affected to any extent. 



Similar tests were made to deter- 

 mine the effects of soil moisture. Plants 

 grown in soils of different water con- 

 tent showed distinct differences in 

 the size of the plants and in fruitful- 

 ness. However, the date of blossom- 

 ing was not affected at all. All plants,' 

 regardless of the amount of water 

 which had been added to the soil dur- 

 ing the growing season, came into bloom 

 on the same day. 



In testing light intensity, some in- 

 teresting data also were secured. Plants 

 were grown in the open and under dif- 

 ferent weaves of cloth which produced 

 different degrees of shading. The shaded 

 plants showed the typical effects so 

 often seen when there is insufficient 

 light intensity; namely, slender growth, 

 increased elongation of stem, enlarged 

 area of leaves, reduced production of 

 dry matter and reduced yield of seed. 

 However, in no case did reduction in 

 light intensity affect the date of blos- 

 soming. In some of the experiments, 

 light intensity was kept continuously 

 at only forty-three per cent of normal 

 light, yet this had not the slightest ef- 

 fect on the time of blossoming. 



Length of Illumination. 



Experiments were finally carried out 

 in order to determine the influence of 

 the length of the daily period of illumi- 



nation. For comparison, plants were 

 grown under natural conditions of light 

 while others were put in a dark" room 

 for varying periods of time each day 

 thoroughout the growing season. 



The results show that in the case of 

 some species the length of the daily 

 period of illumination is an important 

 factor in determining the time of flower 

 production. An example to illustrate 

 this is Aster linariifolius, a form which 

 grows wild in nature. Its blossoming 

 period under natural conditions begins 

 about September 1. A number of plants 

 of this form were placed each day, be- 

 ginning May 13, in a datk room at 4 

 p. m. and taken out again at 9 a. m. 

 The period of exposure to light each 

 day, therefore, was seven hours. Simi- 

 lar plants were kept continuously in 

 the daylight — no artificial light was 

 used — as checks. At the end of thirty- 

 six days the plants which were exposed 

 each day to light for seven hours came 

 into bloom. The plants which were ex- 



The Editor U pleased vrhen 

 a Reader presents his ideas 

 on any subject treated in 



As experience is the best 

 teacher, so do we learn 

 fastest by an exchange of 

 experiences. Many valuable 

 points are brought out by 

 discussion. 



Oood penmanship, spellins and 

 srammar, though desirable, are not 

 necessary. Write as you would talk 

 when doing your best. 



WE SHALL BE GLAD 

 TO HEAR FROM YOU 



posed to normal light conditions came 

 into bloom only after 122 days. The 

 common ragweed behaves in a similar 

 way. When exposed to normal light for 

 only seven hours each day, flowers are 

 produced in twenty-seven days; grow- 

 ing under outdoor conditions, no flowers 

 are produced until seven weeks later. 

 It is thus seen that certain species of 

 plants are either late or early bloom- 

 ing depending upon the daily period of 

 exposure to light. It also is evident 

 that in some species we can regulate 

 the time of flower production by con- 

 trolling the daily period of light ex- 

 posure. 



Not all species, however, behave as 

 do the two illustrations above. In some 

 forms, especially, it seems, in the early 

 blooming varieties, a reduction in the 

 daily period of illumination has but lit- 

 tle effect. This is nicely illustrated by 

 means of four varieties of soy beans. 

 These four varieties bloom under nat- 

 ural conditions in twenty-six, sixty-two, 

 seventy-three and 110 days, respec- 

 tively. When, however, these four 

 varieties are exposed each day to light 

 for only seven hours they come into 

 bloom in twenty-one, twenty-one, twen- 

 ty-four and twenty-six days, respec- 

 tively. It is seen from this that all 

 four varieties thus become early bloom- 



ing varieties, and by controlling the 

 daily period of exposure they all can 

 be made to bloom at approximately the 

 same time. 



Beverse Examples. 



Some species behave in a still differ- 

 ent way. The common cabbage and 

 carrot refuse to respond to a shorten- 

 ing of the daily light exposure by pro- 

 ducing earlier flowers. Hibiscus also 

 produces no flowers when the light ex- 

 posure is reduced to seven hours per 

 day; in fact, it makes but little growth 

 under these conditions. 



Another interesting fact brought out 

 in these experiments is the fact that a 

 so-called annual plant may be made 

 into a "semiannual," while a peren- 

 nial may be made to produce two crops 

 of flowers in the same season. The soy 

 bean, an annual, was brought into bloom 

 in 'from twenty-one to twenty-six days. 

 After the seeds had ripened the plants 

 were exposed to normal light and un- 

 der these conditions new branches de- 

 veloped and a second crop of blossoms 

 and seed was produced early in Septem- 

 ber. Eagweed behaves in a similar 

 way. The species of aster, ordinarily 

 a flowering perennial, gives exactly the 

 same results under this treatment. It 

 produces an early crop of flowers and 

 seeds under the conditions of short days 

 and then later in the season produces a 

 second crop. 



Other interesting and important facts 

 were demonstrated in these experi- 

 ments, but I must defer them at pres- 

 ent. They all show the important 

 relation of light, especially of the 

 length of the daily period of illumina- 

 tion, on flower inception and develop- 

 ment. I have given the most important 

 facts; I believe they will find their 

 application in the growing of some of 

 our greenhouse plants. At any rate, 

 they help us to understand better some 

 of our problems. 



I shall close by quoting, in a some- 

 what modified form in order to simplify, 

 a part of the conclusion of Garner and 

 Allard, who carried out the experi- 

 mental work: The action of the length 

 of day may be tentatively formulated 

 as follows: Flower production can be 

 attained by the plant only when it is 

 exposed to a specifically favorable 

 length of day. The requirements in this 

 particular vary widely with the spe- 

 cies and variety. Exposure to a length 

 of day unfavorable to flower production 

 but favorable to growth tends to pro- 

 duce indefinite continuation of vege- 

 tative development, while exposure to 

 a length of day favorable alike to sex- 

 ual reproduction and to vegetative de- 

 velopment extends the period of flower 

 production and tends to induce the 

 ' ' ever - bearing ' ' type of flowering 

 plant. 



FLOWERS A NECESSITY. 



Henry A. Siebrecht, Jr., of Pasadena, 

 Cal., has the right idea of the way to 

 build up Mothers' day as the great 

 special flower day of the year. His ad- 

 vertising this year features the sen- 

 tence: "Our motto for Mothers' day: 

 'Flowers are a necessity, not a luxury, 

 on this day.' Our prices shall be ac- 

 cordingly." Some florists believe in 

 getting while the getting is good, but 

 Mr. Siebrecht 's idea is to keep prices 

 so low that flowers will be within the 

 reach of all. 



