Soil and Culture 37 
more than half that number — but in mass 
planting or naturalizing, this is sufficient. 
Practically the same difference will be 
found with the lilies. 
Authorities differ on the depth at which 
bulbs should be planted, some claiming 
that deep planting is a cause of failure, 
others that it is the one thing necessary 
to insure success. The bulb’s size has the 
most to do with it, naturally, and the 
nearest that we may come to a general 
rule seems to be to plant each under one 
and a half times its own depth of soil. 
That is, the distance from the top of the 
bulb to the surface of the ground should 
be one and a half times the depth of the 
bulb from top to bottom. This will 
bring the bottom of some bulbs from 10 
to 15 inches or more below the surface of 
the ground, but this is not too much. 
Certain lilies — especially Lilium Harrisii 
and Lilium longiflorum — in addition to 
rooting at the bottom of the bulb, throw 
out other roots from their stems after 
these have grown up from the bulb; these 
