 | There is a considerable degree of variation in shade of color between weeds of different species. |
| | The shade of color of some plants tends to change appreciably over the course of their growing season. |
| | When crops are weeded manually, overall size and leaf shape are taken into account in distinguishing crop plants from weeds. |
| | Selection and genetic manipulation allow plants of virtually any species to be economically bred to have a distinctive shade of color without altering their other characteristics. |
| | Farm laborers who are responsible for the manual weeding of crops carry out other agricultural duties at times in the growing season when extensive weeding is not necessary. |
