Jan* 28, 1S»0. J 
JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 
623 
provided of course that the work is thoroughly and carefully done, 
stud sufficient of the powder is used. Some damp the foliage by 
syringing, and then dust the leaves with sulphur, but I have painful 
recollection of the fatal issues of such a course, although mine was 
perhaps an unusual experience. The foliage bscame scorched 
badly when exposed to bright sun the day following the applica¬ 
tion, presenting an unsightly appearance the remainder of the 
season. Fortunately the practice was needed only to a limited 
extent, as it was initiated at the earliest period of attack. A weaker 
solution applied with the syringe is often fraught with disappoint¬ 
ment, because, no matter how carefully it is done, some of the berries 
are sure to be disfigured by the deposit which is left, and once it 
becomes set it is not easily removed afterwards, and where pre¬ 
sentable bunches are the desideratum, such a course is not likely to 
meet with adoption, at any rate not more than once. It will be 
seen that the most cleanly and effective method of dealing with 
the pest under notice is by sponging, and it is almost beyond doubt 
that Fir-tree oil is the best insecticide for the purpose.—W. S. 
THE HYDRANGEA. 
I WOULD call attention to a plant not by any means so generally 
cultivated as it deserves to be, but which seems to be more affected 
by certain soils than most other plants, though the causes which 
produce so changed an appearance are by no means well understood. 
The plant to which I allude is the Hydrangea, which, though quite 
hardy, is not extensively planted. The variable character of its 
flowers when the plant is grown under certain circumstances has 
for many years been a sort of horticultural puzzle, which is still 
far from being satisfactorily solved. Plants with bright pink 
flowers, and those with flowers of a tolerably good blue are not un- 
fr^uently met with in positions near each other, and apparently in 
soils exactly alike, while plants grown in an ordinary manner for 
the most part have either all pink or all blue flowers, as the circum¬ 
stances of their abode may determine. Now and then certain modes 
of treatment, directed by skilful cultivators, present us with plants 
producing flowers of both colours ; but that every attempt to change 
the colour of Hydrangeas is not attended with the desired success is 
a fact that need hardly be mentioned, and the many failures which 
have occurred have led to the conclusion that the proper means to 
accomplish the end in view are not yet sufficiently understood to be 
depended upon. 
Some time ago it was pointed out that iron rust would not 
always effect the change in colour so much desired. Experiments 
have also been made which proved that much uncertainty existed 
whether the means employed were those absolutely effecting the 
change, or whether such alteration in the colour of the flower was 
not due to some other cause of which we are still ignorant. Be this 
as it naay. Hydrangeas flowering pink and others flowering blue 
have been known for many years, and it remains yet to be proved 
whether iron in some form has anything to do with the change or 
not; but certain it is that the removal of a plant from a soil in 
which this element is only found in very minute particles to one in 
which it exists in greater abundance does not for some time produce 
any change, yet that a change does eventually take place in most cases 
(not all), is also generally admitted. Now to what cause is this 
•change due, and why is not the bloom of other plants affected in a 
like manner? This problem is highly suggestive of study, and 
offers a fair field for experiment. 
In general. Hydrangeas growing in a peaty soil flower blue, 
while those in soil of an opposite character produce pink flowers, 
but there are exceptions in both cases, and this reminds me how 
well the Rhododendron thrives in some of the dells, as well as 
elevated positions, in Cornwall and Devon. I believe the same may 
be stated to be the case in most of the western counties, as far north 
as Cumberland, and probably still further north ; but every hill and 
eminence is not suited to the Rhododendron nor blue Hydrangea, 
and it is wonderful how the line of demarcation is drawn in some 
places. Some years ago I happened to be at a garden near Plymouth, 
and the gardener pointed out the boundary line separating the blue 
Hydrangea from the pink one, which was also the line of demarca¬ 
tion, indicating where the Rhododendron ceased to do well. These 
boundaries, though not so marked as those of land and water, were 
nevertheless very evident. The most probable theory as to the 
cause of such variety in the crust of the earth is that at some early 
convulsion, something was thrown to the top at one place, which 
differed in its chemical constituents from what was exposed at 
another, though the two might be adjoining, and that each through 
the many ages of the world’s history has maintained that difference. 
Though iron in some form may be said to exist to a considerable 
amount in most of the soils producing the blue Hydrangea, and 
though Rhododendrons thrive best in a soil in which this element 
is also found, yet I am not sure that we have not overlooked some 
still more active agent as being the cause in both cases. As a proof 
that iron alone will not always change a pink Hydrangea into 
a blue one, I may mention that large quantities of that metal 
have been at times added to the soil without the desired effect. 
Neither has alum dissolved in the water applied to the plants been 
always attended with success. On the other hand, now and then a 
plant will produce blue flowers without any apparent cause, so that 
we are sometimes almost led to the belief that caprice has some¬ 
thing to do with the matter. It is almost unnecessary to say that 
is not the case, but our knowledge of the cause of the change is far 
from perfect. Time is always required, even when the elements 
necessary to effect the change are present, and a plant that has been 
growing under conditions favourable to the production of pink 
flowers will not produce blue in the first season that it is removed 
to a soil where blue flowers are the rule. This slow change is 
easily accounted for, and need not be commented on, as the 
Hydrangea, like most other deciduous shrubs, sets its bloom buds in 
the preceding autumn, and their expansion the following season 
will be in accordance with the character of the material in which 
they have been formed, but in course of time, in consequence of 
the new food, the juices of the plant become changed, and flowers 
of another character are prepared. This change may possibly not 
be effected, even in the second year, as I have witnessed, but it is 
sure to follow. 
Notwithstanding the general hardiness of the Hydrangea, in 
some cases where it has been injudiciously planted out in a damp 
situation its summer growth is not sufficiently ripened before 
winter sets in, and there is consequently no blossom. A low damp 
situation is by no means suitable to it; a dry, sunny, and airy one 
is more in accordance with its wants, and I believe the largest 
plant I ever saw of it was in a very exposed situation in North¬ 
umberland, elevated considerably above the surrounding country, 
but at the same time drj', the subsoil being the loose shatter stone 
overlying a freestone quarry. This plant flowered pink, as might 
be expected from such a soil; but if it had been growing in a 
valley not more than a stone’s throw from its position, in alt 
probability it would have produced blue flowers, if indeed it had 
bloomed at all. as a black peat morass of considerable depth formed 
the b.ise of this quarry, thus showing how soils of a diametrically 
opposite character may be found in juxtaposition. I am not aware 
whether Hydrangeas were ever tried in this morass, but I have 
seen plants growing on a soil partaking largely of ferruginous 
matter, and the flowers were generally of a very good blue, 
and one season a gentleman brought me some blooms of 
Hydrangea japonica, perhaps a brighter blue than I ever remeniber 
with the old one. The plant was growing on a dry sandy soil, 
where the Rhododendron and others of its kindred were quite 
at home. 
It is certainly remark.able that few, if any, plants show such a 
difference in the character of their flowers as the Hydrangea does 
when planted in soils favouring the two extremes. Most plants to 
w'hich chemical and other substances are sometimes applied exhibit 
a difference in their general health as well as in their foliage, but 
the Hydrangea possesses as robust health in the one condition as in 
the other ; at the same time we may be right in assuming pink to 
have been the original colour. Its change to blue seems to be due 
to some soluble substance contained in the soil and taken up by the 
plant, and carried through its system into the flower buds. There 
may also be some peculiarity in the plant fav'ouriig the storing 
away of such soluble matter as will affect the change. Iron is the 
only substance that I have experimented with, and then only 
with varying success, but alum or some other salt may effect a 
change ; still the light thrown on the subject is far from being 
satisfactory, and discussion may doubtless bring about a better 
understanding. 
I cannot conclude without adverting to a very common disap¬ 
pointment—namely, that this plant will not produce blue flowers 
when grown in a pot and in peat .soil, and water impregnated, 
perhaps, with chalk or lime is supplied to it from a well. Water of 
this kind neutralises the effects of the peat, and the flow'ers are pink 
instead of blue. I believe many of the so-called failures in obtain¬ 
ing blue flowers arise from this and similar causes. I m.ay also add 
that such water given to Heaths and kindred plants growing in 
peat soil is at all times hurtful, as the soil and the water have 
opposite effects ; and in the case of the Hydrangea it is useless to 
expect a good result from a mixture of opposite ingredients, as the 
chemical properties wanted in a soil must not be neutralised by the 
water administered to it possessing those of an opposite character, 
as the object sought after is rather an extreme than a neutral 
combination. Those, therefore, who expect to have blue flowers 
on Hydrangeas ought to be careful what desciiption of water is 
supplied to them, and it is not too much to say that this has really 
more to do with the success of the plants than the soil they are 
