WHY PINK HYDRANGEAS ARE BLUE 
I T HAS long been a sore fact with many a gardener that a 
I lydrangea purchased as pink or blue tlowered may come 
quite otherwise the following season—or, as sometimes has 
happened, both colors appearing on the same plant or 
perhaps an intermediate shade of mauve developed. Though 
the majority of people apparently prefer the pink color, 
a not inconsiderable number greatly desired to have them blue, 
and resort has been had to dosing with alum or iron—a person’s 
experience leading to the advocacy of one or the other method, 
which, however, does not always produce a like result in another’s 
garden. Some varieties of the modern Hydrangea are naturally 
white-flowered and these, it is found, are staid in their color 
habits, keeping an immaculate purity even when the normally 
pink relatives become blue. It is evident therefore that there 
is in the colored plants a definite substance that could in some 
way be influenced through the roots. 
To the amateur gardener the blueness or pinkness of the 
Hydrangea flowers is little more than an interesting or irritating 
perversity, according to the point of view, and the fact that some 
iron scrap, filings, or rusty nails might or might not turn pink 
to blue, if dug into the soil around the roots of the plant, 
added an incentive to experiment, and we had personal 
observation of the influence of alum, applied in solution during 
the growing period, on the next season’s flowers. 
But to the commercial florist, the question of the color is 
serious. Hydrangeas are grown on a large scale for the Easter 
market, and the public demand then is not for blue, but for 
pink. 
The importance of the florist interests in New Jersey has led 
the State Experiment Station at New Brunswick to give atten¬ 
tion to the problem, and Mr. C. H. Connors, a florist by tradi¬ 
tion, and an experimentalist by instinct, in charge of floricultural 
research work at the station, has worked out the solution of the 
problem: Naturally acid soils yield blue Hydrangeas; neutral or 
alkaline soils make pink ones; and it was demonstrated very 
plainly that the desired color may be produced at will by con¬ 
trolling the soil reaction. The iron or alum treatment brings 
about results by its acidifying action and was effective only 
when the soil reaction was near the critical point, unless used 
in large amounts. Grown in a fine quality of woods earth, blue 
flowers are developed, but pink are assured in varying degrees of 
intensity according as lime is added. 
But there is a limit of lime tolerance, to which this plant is 
peculiarity susceptible and beyond which point a totally different 
effect is produced simulating a condition of disease, chlorosis, 
a yellowing along the veins of the leaf and a general off-color 
appearance of the entire plant. This condition is rarely 
brought about by the use of excessive amounts of ground lime¬ 
stone in the presence of a large proportion of well-decomposed 
manure, but it is liable to occur after the use of slaked or 
hydrated limes in excess of the amounts actually necessary to 
bring about the change. This is not to be confused with an¬ 
other type of yellowing due to poor drainage, a not uncommon 
appearance in Hydrangeas grown in tubs in many a front yard 
and porch. Mr. Connors hasfound that a Hydrangea started inan 
acid soil and later repotted into an alkaline soil produced flowers 
in varying intensities of pink in the later growths. In his ex¬ 
periments he has used ground limestone up to the rate of forty 
thousand pounds to the acre. Other plants with the roots 
split and so straddled into two types of soil (although showing 
the weakening effect of the operation) responded, as was ex¬ 
pected, fractionally as to color in the flower and produced flowers 
of different hues on different branches. In brief, the demon- 
strationis cleardimeupto a certain quantity assures pink flowers, 
but beyond that an overdose produces a deleterious effect. 
As to what the individual gardener may do in controlling the 
color of the flower—each one will have an individual problem 
depending entirely on the actual condition of the soil with which 
he starts. It is a case for individual experiment; each one for 
himself, for soils differ, although it has now been ascertained 
that in any good garden soil ground limestone at the rate of 
10,000 pounds to the acre, which is about a 6-inch pot to the 
one-half cubic yard, will be effective in developing pink flowers 
upon Hydrangeas of the hortensis type. 
THE OPEdy^ C 0 LUM: K^ 
Readers’ Interchange of Experience and Comment 
To Organize Southern Gardeners 
To the Editors of The Garden Magazine: 
HAVE read with a great deal of interest “A Southerner’s” letter 
in the Open Column of the July issue. Surely there are many 
enthusiastic gardeners in the Southern States! With the climate in 
our favor, we should be able to do many interesting experiments, but 
nevertheless, most people seem content to grow a few Zinnias, or plant 
a little shrubbery, and let it go at that. 
In England, nearly every community has its annual flower show, but 
since I have been here I haven’t seen one. I only hope Florida’s good 
example will be followed by other Southern States. 1 have some 
Montbretia in bloom now from bulbs planted February 24th. It is 
quite a novelty here, nobody seems to have ever seen any before. 
The remedy would seem to be in Southern garden enthusiasts forming 
a society through which they could compare notes, arrange shows, etc. 
The question is—are there enough of us?—D. Lawley Woodward, 
Decatur, Ga. 
More Plants for a Montana Garden 
To the Editors of The Garden Magazine: 
N THE June number you express a desire to hear from Montana 
readers. Living on the prairie-like land of eastern Montana, my 
wife and i have tried to grow flowers of various kinds. Rainfall is 
limited and the winters at times are very cold, winds having full sweep. 
But 1 might say for the benefit of your correspondent, Jessamine Spear 
Johnson, that we have successfully grown trees such as Box Elders, Ash, 
Cottonwood, Thornapple, Wild Plum, Compass Cherry, Bull Pine, 
Spruce and Caragana as well as various shrubs. We have had good 
success with Dahlias, Gladiolus, Iris, Poppies, native Pentstemon, and 
