CONSERVATIVE WALLS, 
181 
ren to thrive in spite of all deterring circumstances : but see them when the 
itumn frosts and the cold damps of winter follow — they are cut down, and 
3rish. It is one thing to grow a tender plant in the open air in summer, and 
lother to preserve it alive and healthy through a dark cold winter. 
In selecting a site for a conservative wall, considering the point entirely in a 
iltural light, (it has been before viewed as a matter of taste,) a low situation 
[posed to fogs and damp should be rejected ; for it is a well-ascertained fact, that 
ants so situated suffer injury and die in a winter that leaves the same species 
jjrfectly unharmed in a more elevated spot. And again, it is not advisable that 
: alls built with this intent should be in anywise shaded by trees, or even have 
irge trees in their immediate vicinity, as, independent of other injury, the plants 
I sucli places are more liable to be attacked by mildew. 
The borders, moreover, should be as carefully constructed as for a forcing 
inery; well-chosen materials, and ample facility for getting rid of superfluous 
ater must be provided, and efficient steps taken to prevent the roots of one plant 
Dm piercing the soil and pilfering the nourishment intended for a less robust 
sighbour. The soil of course must be varied to suit the species planted ; it will 
i) enough to say here, that all clayey earth of a tenacious quality, and light sandy 
ils that part too freely with their moisture, should be refused ; the first is 
•pecially hostile to the culturist, through the quantity of water which it holds 
I ieping the roots at a lower temperature, and rotting them ; and also because it 
fers a repulsion to the delicate fibrils in their efforts to penetrate it ; the latter is 
viously incapable of affording sufficient sustenance to the generality of plants in 
moderately dry summer. A great depth of soil is quite superfluous, and even 
jurioiis, as it draws the roots away from the surface ; two feet will be found 
ite sufficient, and this should be laid dry, by placing a quantity of draining 
iterials below it. The bottom, too, should have a gentle slope from the wall, 
id be flagged, or laid with some asphalte mixture, so that it may be quite 
: pervious to the roots, and thereby restrain those organs from pushing too deep, 
:;d sucking up matter to be spent in producing a redundant luxuriance, and 
|itinuing growth longer in the season than the sun has power to mature it. The 
badth need not exceed three feet. 
Further, as many of the plants usually placed against a conservative wall, will 
"ry from each other very much in their relative strength, the border should 
! vays be divided into compartments, so that the roots of one plant may^ never 
fringe on the supply of food designed for another. This is a point worth looking 
t wherever promiscuous planting is intended ; for, without such a curb, the 
|onger invariably overpower the weaker. Slate is perhaps the most eligible 
spstance for the purpose, as it occupies little space, and is easily concealed at the 
sl'face. 
I Besides one plant to remain permanently, each of these divisions of the border 
y hold one or two dwarf plants of rapid growth, intended only to remain during 
