These are the shallow trenches in which seeds of many garden plants are sown. Drills made in the open ground are generally made with the garden draw hoe. The onion hoe or even a sharp-pointed stick are more suitable for sowings in the cold frame or where the short rows are to be cloched. To ensure that the rows are straight, use the garden line. For frame rows, a straight piece of wood is more useful.
Care must be taken to make the drills of even depth. The depth should vary according to the size of the seeds being sown. Generally, the smaller the seeds, the more shallow should be the drill. As a rough guide consider the smallest seeds as needing a soil cover of 6mm (0.25in). Larger seeds may be sown more deeply up to a maximum of 5cm (2in). The average depth for flower and vegetable seeds is from 1-2cm (0.5-1in). The width of a seed drill depends on what is being sown. Seeds of most garden plants are sown in a single straight row in V-shaped drills. Flat-bottomed, rather wide drills are best for some vegetable sowings, such as those of peas, where double or even treble rows of plants are to be grown close together.
Should the soil be on the dry side as it so often is during late spring and summer, the drill should be flooded with water before sowings are made. Sow when the water has drained away. After sowing refill the drills by drawing the soil into them with the back of a rake. On light, sandy soils it is sometimes an advantage to tread lightly along the rows after sowing (see also Seed bed).
A seed drill is drawn with the edge of a hoe along a garden line.