What the heck is an inch a week?
So we have all seen the person out in their garden on a hot, sunny summer day, with hose and hose end sprinkler in hand, gently spraying a fine, delicate mist of water onto their plants... It drives us insane when we see this - it is one of those ‘stop the car I have to yell at someone’ moments…
Don’t get us wrong – we love that that person cares for their garden and is making the time to be in their garden… It is the ‘gentle mist of water on a hot sunny day’ bit we struggle with, as typically all that's doing is wasting water – and, at worst, can even damage the plants.
We have heard folks talk about ‘an inch of water a week’… Which is in many cases, not the right amount. Sigh.
So – let's start with the ‘what the heck is an ‘inch’ of water?’… Rainfall is measured in cm in most countries, or inches in that largish country just a wee bit south of us. If we had to add an ‘inch’ of water to a garden, we would add about 60 US gallons to 100 sq ft (about 240 litres to 10 sq m). On a normal week with reasonable rain, we are not adding any or much extra water to an established garden.
The problem here is starting with: what is a normal week, and what happens when it gets really hot? Plus, some plants need more water than others. As all rules of thumb are meant to be broken, if we are having a hot summer – with both warm days and warm nights, then we will have to look at more water.
But how much hotter and how much ‘more’ water might we need? Well, that then brings in the ‘other’ factors including what plants you are growing, what you soil is like – and if these are newly planted plants or plants in containers… add more water.
Generally, veggies will want a little more water than an established landscape garden. Some flowering annuals are thirsty as well – New Guinea Impatiens and some of the big tropical-like Elephant-ear leap to mind. Most hanging baskets and patio pots are also thirsty as they get beaten up by the wind, and the sun can bake the outside of the pots.
For thirsty gardens like veggies, there is a fun equation: if the average temp gets over 15 degrees C (average of day-time high and night-time low) – then add another 1.4 cm water for every 6 degrees C increase. That makes sense and is a generally good guideline for your vegetable garden. Hanging baskets and patio pots need to be looked at daily in the summer to see if then need a drink. We use the ‘stick your finger’ in the soil trick – and water well if the finger is dry to first knuckle. We water with a gentle water ‘breaker’ rather than a sprayer attachment to avoid spraying the plants, and lets us get the soil wet without blowing all the dirt out of the pots.
A few other things to think about….