THE BLUE HYDRANGEA, 



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THE BLUE ] 



" In countries where the soil is granitic, schistic, 

 ferruginous or crystalline, such soils as abound in 

 Limousin, Brittany, or in the Norman peninsula, 

 these plants are remarkable for their beauty. Though 

 so much has been written and said about the most 

 certain means of obtaining the desired blue colour, 

 the problem would still be unsolved but for an oc- 

 currence some years ago that was put to practical 

 profit. 



Near to Angers there isalake known as St. Nico- 

 las, near which the sub-soil, composed of flint, silex, 

 and sand, is covered with a deep layer of vegetable 

 mould, which the gardeners of the district purchase 

 for a high price and make use of or sell as ' soil for 

 Blue Hydrangeas.' It is a mixture of flint, roots, 

 and half decomposed leaves, and is beaten up and 

 pounded and then riddled for use. The result is a 

 mould of a peculiar brown colour, greasy to the 

 touch, porous, and absorbing water with difficulty. 

 Used in the pot-culture of Hydrangeas, the plants 

 show vigorous growth, the leaves assume an intense- 

 ly green colour, the stems are almost black, and the 

 flower-heads a uniform indigo-blue colour. It is 

 strange, but a fact, that if the soil used for plunging 

 the pots, when arranged on planks for summer cul- 

 ture and convenience in watering, happens not to 

 be this particular soil, and a single rootlet escapes 

 from a pot and reaches it, it causes the flowers 

 to take a rosy colour. I had been struck with this 

 singularity, and thought that the presence of lime 

 in the soil accounted for this change in colour; but, 

 as I wanted to be sure, I asked M. Louis A. Leroy, 

 President of the Societe d'Horticulture d'Angers, 

 to give me a little of this soil for analysis, which he 

 willingly did, sending me also certain information 

 gathered from his own observations, as also those of 

 his friends. In this way I got to know that the first 

 experiments made with the St. Nicolas earth had 

 not been conclusive, and it had been only after re- 

 peated trials that it was found necessary to do the 

 following things : — 



"(i.) Wash all roots of Hydrangeas to be 

 potted in the special soil. 



" (2.) Continue this pot cultivation for a year, 

 taking care to plunge the pots in like soil of suffi- 

 cient depth to accommodate the roots as they escape 

 from the pots. The least contact of a root with 

 common soil will cause the blue colour of the plant 

 to change to a dull purple. 



" The soil of Angers and its environs is chiefly 

 composed of slate schist, with a good deal of iron. 

 Hydrangeas in a northern exposure and occupying 



a place under the gutter of a slate roof frequently 

 take on a blue colour. 



"The following is the result of an analysis of 

 the soil for Blue Hydrangeas made by M. Emile 

 Aubin, of the Societe des Agriculteurs de France. 

 The mixture contained 76 per cent, of fine earth : — 



" Physico-Chemical Analysis. — Flint, 24-00 ; sili- 

 cious sand, 6i'8o ; clay, 2*16 ; lime, 0-09 ; orga- 

 nic matter, 7*55; humus, 0-91 ; water, 3-49; total 



IOO'OO. 



" Chemical Analysis. — Nitrogen, 0*4103 ; phos- 

 phoric acid, 0*1168 ; lime, 0*0504; magnesia, 

 0*2000 ; potash, 0*0850 ; soda, 0*0043 '■> oxide of 

 iron, 3*4100 ; sulphuric acid, 0*0857. 



" The soil, it will be seen, is essentially silicious, 

 very rich in organic matter and in humus, well pro- 

 vided with nitrogen and phosphoric acid, but exces- 

 sively poor in lime and potash. The result of the 

 analysis shows that the Blue Hydrangea abhors the 

 slightest part of contact with a lime soil." — Ed. 

 Andre, Revue Horticole. 



M. Bouret, of Nice, also writes as follows to 

 the Revue : — " Ten years ago I planted a hedge 

 of H. Hortensia at the foot of the north front of 

 the Chateau d'Asson (Vendee) in a granitic, argilo- 

 silicious soil, therefore containing very little lime 

 and phosphoric acid. In ordering my plants I in- 

 sisted on having only such as bore rose-coloured 

 flowers. But with the first appearance of the flowers 

 there was a disagreeable surprise ; there were plsnta 

 which bore only blue flowers, and others with only 

 rose-coloured flowers; others, again, had mingled 

 blue and rose-coloured blooms, or variegated 

 blooms. I blamed the seller of the plants, who 

 protested that he knew by the evidence of his own 

 eyes that the plants only bore rose-coloured flowers. 

 My curiosity being aroused, I caused the soil to 

 be dug over, and I found mixed with the earth a 

 quantity of slate off the roof. But why both red 

 and blue flowers? The thing was explained when 

 it was discovered that although the centre of the 

 building was roofed with (Angers) slate, the two 

 flanking pavilions were tiled. Where there were 

 slates the flowers were blue, in other places they 

 were rose colour. As for the two colours growing 

 on the same plant, the explanation is, that if a root 

 came into contact with a slate, the corresponding 

 branch bore blue flowers ; otherwise it produced 

 rosy flowers. On asking old gardeners of the loca- 

 lity whether they were able to obtain blue flowers 

 at all, the reply was, ' Yes, if we pound up slate 

 and mix it well with the soil.'" 



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