Watering plants is child's play. But knowing how to water your plants is the difference between a climate-appropriate garden, and one that is wastefully lush, or unnecessarily dry. There's a big difference between watering your indoor plants and those in a garden. No plant evolved to live in your living room, and the way you water can compensate for this... or leave your plants struggling.
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Watering Indoor Plants
There is an amazing technique for watering your indoor plants. It overcomes two problems of growing plants indoors; plant nutrition and water distribution. It is called dip watering, and I go into detail about it in this article: How to Water Indoor Plants. In this article, I will cover watering your outdoor plants, but first, there's an important difference between plants in the ground, and plants that are in pots outside.
Watering Outdoor Pot Plants
If you're hand watering, the quickest method is to flood the top part of the pot with the hose. Then wait for it to bubble down until you can see the surface of the potting mix. Repeat once. You're done.
If you don't like the sound of regular hand watering, I recommend setting up a system to irrigate the pots. Potted plants dry out much quicker than plants in the garden, and they are less resilient.
Watering Plants in the Garden
Plants in your garden need regular watering for the first season (at least) after they are planted. They also need regular watering when they are young and extra water when the weather is hot, dry, or windy. They will use less water if they are thickly mulched and 'fertilised' with organic matter (for more information see my article on How to Grow Plants).
Why we Water
There's a lot of advice online about watering your garden. "Water deeply, once a week!" "Plant a waterwise garden and don't do extra watering!" "Water X amount per week!" None of it is inherently wrong. But you can make better choices when you know what the water is doing once it leaves your hose. Moisture in the soil underpins the whole soil food web. Without moisture, bacteria shut down, fungi shrivel, and plants wilt. So, what does happen after the droplets hit the ground?
Water's Journey From Hose to Roots and beyond
Water droplets hit the mulch and drip down to the soil. From the surface, they soak in, spreading outwards through the clumps and gaps that make up the soil 'texture' by wicking. Water simultaneously flows downwards, drawn by gravity. Wherever it goes, moisture brings life to the soil. It allows bacteria to move around, worms to stay hydrated, and roots to suck up nutrients and pump out sticky 'exhudates'. These are the sugars that the plant releases to 'pay' the bacteria and fungi for the nutrients that it needs. Living soil forms a sponge that holds enough water where it is needed.
As thriving plant roots reach further down into the subsoil they support soil life down there, growing your topsoil downwards. building soil with life is much, much cheaper and easier than paying a landscape company for topsoil, which then must be spread out, smoothed, fertilised, seeded or planted etc.
Water droplets from rain or a hose hit bare soil with force. Splashes break up the texture, ripping apart surface bacterial communities. Bare soil also allows moisture loss to evaporation; drying out and slowing the dance of life. All that survives in this tough environment are established plants and the toughest of seedlings. We generally call those weeds, breaking out the hoe to remove them.
The Problem of Excess
Living soil is like a sponge that will take up water until it is saturated. Excess water has only two directions to go; downwards or across the surface. When water is added slowly, excess trickles downward to join the water table. When the soil's ability to soak up water is overwhelmed (like in heavy rain), excess flows away over the surface to join the stormwater drains or the nearest river. There's no point in over-watering your plants. Keeping your soil spongy allows it to soak up copious amounts of water and replenish aquifers during rain.
Cover your garden beds with thick mulch. This keeps the sponge of your soil active and will help your plants thrive.
How Much to Water
Many of our favourite plants originated in environments that had regular rainfall. These thrive with regular watering. I don't agree with the advice to water deeply once or twice a week. This is because of the role of water in keeping the soil sponge active. I recommend you water your garden with a small amount of water every day. To work out how much is reasonable, I take the annual rainfall for your area and divide by 365 to get a daily average. Run your hose into a bucket for a minute to discover your actual flow rate. Then divide your daily average by your flow rate and you'll know how many minutes to run the hose for.
Hand Watering
Some people like to hand-water. They feel it is like meditation. Hand-watering early in the day after the sun has risen and warmed the garden is ideal. This ensures that any overspray will dry off the leaves before the day gets too warm (or before nightfall if the day is cold).
The worst time to water is in the evening or overnight. When the heat of the day has gone, water droplets will stay on the leaves creating humidity and encouraging mildew. However, if you're time poor and your plant is water stressed, water it when you can of course!
Irrigation Systems
An irrigation system can be as simple as a soaker-hose connected directly by a hose extension onto your tap (you might call it a faucet). They can be snaked through the garden bed under the mulch, providing water inexpensively to your plants. At the opposite end of the complexity scale, you could install a custom-designed grid with regulated flow drippers, vacuum breakers and flush valves. Irrigation tubing should always be run under the mulch as this keeps water off the leaves, stops the hose from photodegrading and reduces evaporation.
Choosing an Irrigation Controller
An inexpensive mechanical timer is a step up from connecting the hose directly to your tap (faucet). Start watering by turning these on at the tap and they shut off after a set time, so you needn't remember to turn the water off. The next level up is a dumb electronic timer. You can 'program' these to come on at the same time every day—rain, hail, or shine. Climbing the money tree from there you find all sorts of smart systems. These have functions like delayed watering if rain is forecast, and remote operation from your phone etc. The 'smart controller' can be a plant-saver if an unexpected hot, dry day falls when you are not at home.
This happened to me—I was away and the weather changed. I lost a ton of established plants that I had been saving in pots. The purchase price of a smart water controller would have been far lower...
Now You...
Have you ever wondered how best to water your plants? Have you lost plants on hot days because you weren't home to water?
Do you prefer to only plant endemic plants in your garden? Tell me in the comments.
