The short version: Push a finger into the mix to the second knuckle, about 5 cm, midway between stem and rim. Dry and warm at the fingertip means water today; cool and damp means wait a day and check again. In a bed, check at 10 cm with a trowel. The surface dries first and tells you little, except in seed trays.
How to do the test
- Check in the morning, before the sun has dried the surface.
- In a pot, push a finger in to the second knuckle, halfway between the stem and the rim. Notice whether the mix feels cool, whether it feels damp, and whether any clings to your skin.
- In a bed, push any mulch aside, dig a small hole with a trowel to 10 cm and squeeze a pinch of soil from the bottom. Cool and damp is fine; loam holds together when moist, sand will not, so go by feel. Dry and dusty wants a slow, deep watering to well below 10 cm; dig again an hour later to check.
- Seed trays and punnets are too shallow for a finger, and germinating seed must not dry out. Water gently or from below as soon as the surface pales, then let the tray drain.
Reading the result
- Dry at 5 cm in a pot: water until it runs freely from the base.
- Damp at 5 cm: leave it. Most vegetables prefer a cycle of thoroughly wet, then moist, then wet again, over mix that stays sodden.
- Wet at 5 cm but the plant is wilting: do not add water. On a hot afternoon it may be heat. If it is still limp in the morning, the trouble is at the roots: check that the drainage holes are clear and the pot is not sitting in water.
- Water runs straight through and the mix is still dry: the mix has become water repellent. Water slowly in two or three passes, or stand the pot in a tub of water until the surface is damp, then lift it out to drain.
Two checks that back it up
Lift the pot. A dry pot is noticeably lighter, and after a few weeks you will know the weight of a watered one. And watch the plant in the morning: a plant that is limp at 7 am and dry at 5 cm is thirsty, while a plant that droops at 3 pm on a hot day may be losing water faster than its roots can pull it in, even from moist mix, and often stands up again by evening, so feel the mix before you reach for the hose.
Your finger is a better guide than a fixed watering schedule, and it comes with you.
Related reading
Once you can read the soil, every packet from the vegetable seed range gets an easier start.