132 REMARKS ON HYDRANGEA HORTENSIS. 



ARTICLE VTI. 



REMARKS ON INDUCING THE HYDRANGEA HORTENSIS TO 

 PRODUCE BLUE FLOWERS. 



BV CLERICUS. 



Several admixtures of compost have been from time to time recom- 

 mended in -which to grow the Hydrangea hortensis, in order to cause 

 it to bloom with blue flowers. I have tried all I have noticed, and 

 the following is the most successful. 



Very fine iron filings, and grinders dust (that is, the fine sandy 

 substance that is found under the stone -wheels of the knife-grinders) 

 composing one part. Pure yellow loam from a hedge row one part, 

 and another equal part composed of the same proportions of rotten 

 leaf soil (or rotten wood) and bog peat. In this compost well incor- 

 porated, I put several plants which had only bloomed rose colour 

 previously. The first season the flowers on every plant were of a 

 pale blue. They were repotted in spring following in the same kind 

 of compost, and the blossoms were of a much deeper blue. The 

 third season they were of a rich blue, and have invariably been so 

 every successive season. The rough drainage in the pots I formed of 

 pieces of stone taken out of the yellow loam, and pieces of turf where 

 the yellow loam was collected, with a handful or so of rusty pieces of 

 iron nails intermixed. These formed the drainage, which was at 

 least two inches deep. 



It is certain that the iron filings cannot act directly upon the 

 organism of the roots, but is gradually converted to an Wcycle, by the 

 decomposition of water, directly or secondarily by that of the vege- 

 table contained in the compost. In either case it is not to be expected 

 that the iron would be dissolved and conveyed through the sap 

 vessels into the floral organs; unless, indeed, some vegetable acid 

 were produced capable of acting upon the iron at the moment of its 

 oxydation, and so form a soluble chalybeate salt. It is however evi- 

 dent that the plants absorbed a certain something from the iron, which 

 became the direct agent in producing the change of colour. It is 

 certain that however fine the filings of the iron may be, the particles 

 cannot be absorbed in that state, they must therefore be so changed 

 as to beeome soluble ; or, by attracting oxygen from the moisture of 

 the soil, and leafy remains, &c. be converted into an oxyde. 



