WEEDS OF THE FIELD 261 
depth most favorable for quick and early growth. Certain 
plants, like buckwheat, that grow up quickly, smothering the 
weeds, are often used to clean a weedy field. Potatoes, on 
the contrary, being slow to appear above ground, are certain 
to be beaten in the occupation of the soil by many weeds. 
So they are often tilled just before they appear above the 
ground. The weed seedlings are easily killed when little. 
Tillage breaks their mooring in the soil. The weeds are thus 
1 
2 3 
Fic. 100. Sun prints of weeds, showing the extent to which they shade 
the ground. 1,paint-brush; 2, moth-mullein; 3, evening primrose; 
4, creeping spurge; 5, door-weed or goose-grass. 
given a second setback, while the stout potato shoots come 
along uninjured. The farmer ought to be something of a 
naturalist, for his success in handling plants must needs be 
based on observations of their habits, their powers, and their 
requirements. 
The farmeranight save himself much labor of exterminating 
weeds in his fields, if he was more careful not to encourage 
their growth outside the fields. He provides too many 
reserves for them in roadside and barnyard and fence-row. 
Enormous crops of weed seeds are matured in such places. 
It is not enough to keep the fields clean. The fence-row 
may be a source of reinfestation. A clean field may 
