Litres a week, where they come from, and why most weeks need no watering at all.
One millimetre of rain is one litre of water on a square metre. The whole arithmetic of watering follows from that sentence: how many millimetres a week a plant takes, how many the rain gave, and the difference is what you carry.
| What | Per week | How often |
|---|---|---|
| lawn | 25 L/m² | 2 waterings |
| bed of low-water plants | 10 L/m² | every 7 days |
| mixed bed | 18 L/m² | every 4 days |
| bed of thirsty plants | 28 L/m² | every 2 days |
For 100 m² of lawn that is 2,500 litres in a dry week, two and a half cubic metres. It is why the rain tank in a Verdlo plan is sized for three dry weeks rather than for one watering.
Those figures are a dry summer week, and a week like that happens a few times a season. Verdlo works the week out from evaporation: the forecast says how much water the sun, wind, heat and humidity will take (ET0, FAO-56), multiplies it by the plant's crop coefficient and subtracts the rain that fell and the rain that is coming. In a September week with 24 mm of rain, the answer is no watering at all.
These are planning figures for established planting in a temperate climate, not a measurement of your garden. Sandy soil drinks more, clay less and less often.
The studio draws a plan for your own plot and picks plants that suit its light and soil. It needs no account.
Try the studioThe material ranges Verdlo computes every plan from, and what they leave out.
What takes clipping, how close to plant, and what not to plant on a boundary.
Which plants drop out of a plan when a child or a dog uses the garden, and why.