Watering should be simple, right? But it’s an area of gardening that often causes the most confusion. Read on or watch our video to find out how effective watering can save your time, money, and course, precious water!
1. Watering Too Much or Too Little
Every gardener is guilty of overwatering or underwatering from time to time, whether it’s because we ‘just want to be on the safe side’ or we simply forget! So here are a few tips to help you get it right.
The symptoms of plants struggling with too much or too little water are often the same: drooping or curling leaves and a sorry-looking appearance. Be guided by the current conditions: if it’s hot and you haven’t watered for a few days, chances are your plants are gasping for a drink! If it’s dull and cool and you’ve been watering every day, your plants are probably drowning.
There are a couple of ways to tell if your plants need watering. First, perform the finger test: simply push a finger an inch or two down into the soil to feel for moisture. Cool and damp means the plant is doing fine; dry and warm suggests it’s time to water.
You can also carry out the weight test: pick up a container or tub and gauge its weight. I can even judge the weight by simply pushing the container with my foot to tip it slightly. With experience you’ll learn how heavy it should be.
If you’re growing in pots, bear in mind the size of the container. A well-watered large container has more available moisture for plants to draw on, which means they should need watering less often than a smaller pot. Pick up or push your pots to judge their weight and how moist they are, or test with your finger.
Temperature, how much direct sunshine plants are getting, and how windy it is are all factors to consider when trying to work out how much water to apply and how frequently.
2. Incorrect Watering Technique
The way water is applied to your soil directly affects how effectively plants are able to use it. If you pass over the soil quickly the surface may look wet, but the moisture doesn’t penetrate deep down to where the roots are.
The first thing to do when your soil is dry is to water it thoroughly. I tend to methodically water one bed at a time and then move on to the next and then the next. But then I’ll go over the whole lot again and repeat the process. This means the first drenching has a chance to drain down into the soil so it’s receptive to the second drenching, which drives that moisture deeper down. Watering like this means you can water a little less often. In my cooler climate that may be just once a week or twice a week in the very hottest weather.
Aiming water at the base of plants helps make best use of the water you add. Water that hits the leaf surface is wasted, because most of it evaporates rather than going down to the soil where it’s needed.
This is where soil-level irrigation comes into its own. Drip irrigation, soaker hoses – anything that delivers water at ground level is going to get much more water to the roots than water applied from overhead. I prefer to water by hand however, because it gives me an opportunity to inspect my plants and keep a close eye out for problems as I move between them.
Avoiding wetting the leaves can also help reduce the spread of some diseases, for instance blight on tomatoes or potatoes. It can be hard to avoid wetting the leaves of seedlings and young plants though, so don’t stress about it too much.
Not all plants should be given the same amount of water. Seedlings and shallow-rooted crops like beans may need a more shallow watering more often as they can’t draw on moisture from far down in the soil. Root crops and other veggies that delve deeper will be more self-reliant and can go longer between waterings.
Large plants that producing juicy, fleshy fruits need plenty of water – cucumbers, tomatoes, and courgettes for instance. More water in equals more fruit out. Consistency of watering is important too. Don’t let them dry out too much before the next watering, or fruits are likely to crack or split as they try to cope with the sudden growth spurt this promotes.
If you have a containers that has dried out so much that the potting mix that has shrunk away from the walls of the pot, it’s harder to re-wet it. Water applied on top will simply run down off the top and down the gap at the sides. A more effective way to re-wet it is to stand the container in water for an hour or two until it has rehydrated. Don’t let it get to this point – regular watering should avoid this ever happening!
3. Watering Plants at the Wrong Time
It’s tempting to water in the middle of the day – after all that’s when plants are hottest, and probably thirstiest right? Wrong! Yes, they’re hot, but if you’ve watered earlier in the day they’ll be just fine. There’s a bit of a hierarchy of when to water, and top of that is first thing in the morning.
Watering in the morning gets plants off to a flying start. They’ll have plenty of soil moisture to draw on and will be stronger to face the heat of the day. It will also mean the soil surface will dry off as the day progresses, meaning fewer problems with soil-borne pests like slugs or diseases. Watering your plants in the morning is a great way for a gardener to start the day – a little commune with nature when it’s quieter as you psych yourself up for the day!
But not all of us are morning people, or have time in the morning. Or maybe you just prefer to wake up slowly, with your feet up watching your favourite YouTube channel before rushing off to work? If so, don’t worry - watering in early evening is the next best time of day. There’s still time for the soil to dry out a little, and the worst of the heat of the day should have passed, ensuring less evaporation from the soil surface and plenty of moisture left in the soil to support plants the following day.
Clearly this is where an automatic irrigation system – set to a timer – can prove invaluable. Set it to water at the optimal time of day and let the system do the work for you.
Sometimes plants will wilt a little during the heat of the day, then bounce back in the evening once temperatures have recovered, so don’t rush to water while it’s still hot. It’s best to stick to morning or evening unless your plants are in a really bad way.
4. Not Collecting Enough Rainwater
Rainwater is best for our plants. Mains or city water is good enough, but with the high levels of chlorine used to treat the water it’s not ideal, and it can be alkaline, which is a definite no-no for acid-loving plants like blueberries. Rainwater is free, unlike treated water which can be quite costly in some areas, especially water-stressed regions.
A rain barrel attached to an outbuilding or greenhouse, or even your house roof, can collect an impressive volume of water. Connect multiple rain barrels together, or even use an IBC (or several!) for maximum capacity. Make sure rain barrels are kept covered to prevent birds and other creatures falling in, to reduce problems with bugs like mosquitoes, and to prevent algae forming. Check out our rainwater harvesting tutorial for more on this.
5. Not Covering the Soil
Even in my temperate climate we often get surprisingly long periods without any rain – up to a month in some cases. That, combined with a heatwave and strong (for us!) sunshine can do a good job of drying out the soil till it turns dust dry and rock hard.
The best way to keep moisture in the soil for longer, and thereby reduce how often we have to water, is to cover the soil. I wouldn’t go out under the hot sun without some sunscreen, and soil shouldn’t have to either.
Mulches slow down evaporation when they’re applied after a thorough watering, locking in moisture for longer. Organic mulches (mulches that will eventually rot down into the soil) are best because they will feed the soil as they break down, but any cover is better than none in a hot summer. If it’s really hot, you can use shade cloth to slow evaporation.
You don’t need to spend much on fancy mulches. Garden compost, leafmold, and pine needles all work well. I use straw on the potato beds and around tomatoes, and dried grass clippings from my lawn around leafy greens and so on. You could also use bulkier mulches like wood chips around fruit trees and bushes.
Mulches also prevent soil from splashing up onto the foliage, which is great for crops like tomatoes that are prone to soil-borne diseases. It cushions the soil so that when you water or if it rains heavily, the soil surface doesn’t become compacted or develop a hardpan and run off over the surface. And it keeps the soil cooler in hot weather, which is great news for soil life – everything from earthworms down to the micro-fungi that help our plants thrive.
Shallower rooted crops will especially appreciate a good mulch, and you can mulch containers too of course.