| Clue | Source | Date |
|---|---|---|
| Various soils | Universal | 14 Jul 2017 |
| Various soils | ||
| Potting soils, for example | Wall Street Journal | 29 Oct 2016 |
| Various soils | USA Today | 15 Nov 2015 |
| Various potting soils, essentially | Universal | 25 Jan 2015 |
| Various potting soils, essentially | ||
| Various soils | ||
| Agronomist's samples | ||
| Potting soils, e.g. | ||
| Topsoils and silts, e.g. | ||
| Grimes | ||
| Potting soils, e.g. | ||
| Potting materials | ||
| Agronomist's samples | ||
| Detergent targets | ||
| Mud, dust and grime | ||
| Various soils | ||
| Topsoils and silts | ||
| Soils. |