350 WINDOW GARDENING^ AND [chap. xi. 
It is also a common fault to put plants 
kept in rooms, into too large pots; or, as the 
gardeners express it, to over-pot them. This 
has always a bad effect. If the soil be good, 
and not over-watered, the plants will indeed 
grow rapidly; but it will be to produce leaves 
and branches instead of flowers: and if the 
soil be over-watered, the mass of soddened 
soil round the roots has the same effect upon 
them as stagnant water in the saucer. The 
soil should always be in such a state as to 
admit air with the water to the roots; and 
this it cannot do when it becomes a blackened 
paste by being saturated with water. At 
the same time frequent repotting is often 
absolutely necessary to keep the plants in a 
dwarf compact habit of growth, and to pre¬ 
vent them from being drawn up. The way 
in which gardeners ascertain when repotting 
is necessary, is by turning the plant out of 
its pot with the ball of earth attached; and 
if they find the roots look white round the 
outside of the mould, then the plant should 
be transferred to a larger pot; but only one 
size larger: afterwards it may be repotted 
again if necessary, but always to a pot only 
