198 IOWA DEPARTMENT OF AGRICULTURE 
done as much as the present system of leasing farms; some renters are 
good farmers, they clean the crop as carefully as the owner would, but 
many of the leased farms are nurseries for the growing of weeds and 
from these places spread to adjacent farms. 
There are two ways in w^hich weeds spread, namely by the production 
of seed and by vegetative propagation. The habit of plants determine 
whether the weed is readily destroyed or not. The Bull Thistle, Foxtail, 
and Ragweed are all readily destroyed because of their annual or bien- 
nial nature, on the other hand Quack Grass, Canada Thistle, Morning 
Glory and Horse Nettle are not readily destroyed because of their per- 
ennial character. Again, the seed habit and its manner of dispersal in- 
fluences the abundance of the weed. The seeds of the Bull Thistle, Dan- 
delion, Wild Barley, are scattered widely by the wind and become a 
menace to a clean field because the seeds are scattered by the wind. 
We will discuss this subject under the following heads: Clean seed; 
garden and ornamental plants; railways; highways; rotation of crops; 
treatment for annual crops; treatment for biennial weeds; treatment for 
special weeds; quack grass; treatment with chemicals; Canada thistle; 
morning glory; milkweed; horse nettle; dropseed grass; cocklebur; sqir- 
reltail grass; wild barley; Indian mallow or butter print. 
Clean Seed. An excellent way to prevent the spread of many of the 
noxious weeds is to plant only clean seed. Throughout the state of Iowa 
there are evidences everywhere of weeds, which have been scattered by 
seed. Rye, Hop Clover, Wild Carrot, Buckhorn, Mustard, Bracted Plan- 
tain, and Dock which are scattered by means of seeds of various crops in 
which these seeds are found. For instance, in many parts of the state 
the Wild Carrot and Buckhorn are common in clover meadows. These 
weeds have been found so frequently in clover seed that there can be 
no doubt that the most important means of scattering has been by means 
of these impure seeds. Again, Wild Oats in a few places in northern 
Iowa is plentiful and is scattered here largely by means of cultivated 
oats. Mustard has been widely distributed in the state by sowing the 
seeds that contain the mustard seed. In northeastern Iowa we observed 
during the last summer considerable Yellow Hop Clover along the road- 
sides. This had evidently been scattered by clover seed from adjacent 
fields. Here and there we have occasional reports of the abundance of 
Dodder upon clover and alfalfa, and the occurrence of Chicory and Knap- 
weed in alfalfa fields. 
All of this goes to prove the necessity of enforcing the law passed at 
the last session of the legislature with reference to the sale of agricul- 
tural seeds, and the law should include garden seeds as well. I believe 
that I am safe in saying that the majority of the Iowa seedsmen are 
trying to live up to the present law and that we should co-operate with 
these people as much as possible and that much good has been derived 
from the law in an educational way. 
Garden and Ornamental Plants. In many parts of the state there are 
found weeds of very dangerous classes which have been largely introduced 
by means of the garden, that is to say, these weeds were at first planted 
for ornamental purposes and have now spread to the fields. As an illus- 
tration the Bouncing Betty and Toad-flax, which are very troublesome 
