The Dandelion in Colorado 
21 
percentage of bloom the next season. It should be the aim, how¬ 
ever, to entirely prevent the re-seeding of the lawn each season 
from plants permitted to go to seed upon the premises. Where 
neighboring lawns are badly neglected, spraying is necessary at 
least every alternate year together with some digging or other 
treatment in order to keep the pest under control. The spray¬ 
ings, to be most effective, should be repeated as soon as the dan¬ 
delions have partly recovered from the first treatment, an interval 
of about three weeks between sprayings having been found de¬ 
sirable. The plants should be allowed to put out new leaves, the 
time for the next spraying being due a little before the new fol¬ 
iage is fully grown. In this way the plants are forced to use up' 
their reserve material in the root by growing a new set of leaves 
which are again destroyed before they are able to do much in the 
manufacture of a new food supply. 
Application of the Spray .—There appears to be some rela¬ 
tion between the method of applying the spray and its effective¬ 
ness. Thus, it has been found that better results are secured by 
using* a fine, forcible spray, which drives the solution w^ell into 
the crowns of the dandelions, than by sprinkling it on with a 
hand sprinkler. For this reason a good spray pump should be 
used, capable of producing a strong, spreading mist-like spray. 
For the small lawn, a good bucket pump with brass cylinder and 
fittings is desirable. The solution of iron sulphate shauld be made 
and used either in wooden or graniteware vessels, as it is apt to 
discolor and corrode iron surfaces, even though galvanized. For 
larger lawns, a spray pump attached to a barrel mounted on wheels 
forms the most serviceable outfit, while for large areas, such as 
parks, a power outfit, like those used for field or orchard spray¬ 
ing, is the most practicable. 
It is desirable to cover every part of the lawn surface as 
evenly as possible, in order to hit any small plants that may not 
show plainly at the time of spraying. Where the plants are espe¬ 
cially numerous, however, the spray may be applied more freely 
than elsewhere. One of the difficulties in applying* the spray 
evenly over the whole surface may be largely overcome by moving 
the spray nozzle back and forth in one direction across the lawn 
and then going over it again at right angles to the first, using only 
half the total amount each time. 
Effects of the Spray.—Observations upon the effects of the 
iron sulphate spray on the foliage of the dandelion were not made 
with a view to the physiological explanation of its action. The 
effectiveness of common salt as an herbicide is said to be due to 
