Watering your garden is an important job. Plants need water in order survive and thrive.
Ideally you want to have happy and healthy plants using the least amount of water to help save on your water bill and conserve the precious resource.
Plant cells consist of up to 70% water. They utilise the water to perform all their vital functions, including growth, transpiration and photosynthesis. During photosynthesis, plants take in Carbon Dioxide and release Oxygen and water into the atmosphere, so to compensate for this loss; the water must be replaced through the plants root system.
Here are some ideas on best practice to water effectively.
Something as simple as the time you water not only saves water, it is also provides greater benefit to your plants.
The best time to water is in the early morning or the evening, when cooler temperatures will greatly reduce the amount of water lost during watering through evaporation. Watering at these times will ensure better penetration into the subsoil around the root systems.
Watering deeply in the morning or evening allows the plants to soak up the water before the high temperatures of the day. If they are satiated with water when the heat hits, they will be more resilient.
Don’t be tempted to sprinkle the hose around on a hot day – it might make you feel cooler but it won’t do your plants any good at all! In hot winds, the water will just evaporate in a matter of minutes. Because the water is evaporating at such a fast rate you will end up just wetting the surface of the soil, which can encourage shallow root growth. Watering at a time when the moisture will remain in the earth encourages the roots to proliferate lower in the soil profile, which enables them to stay cooler and draw from the water reserves lower in the ground.
In some areas wetting the foliage on a hot day can actually scorch or burn delicate leaves by magnifying the sun’s rays. The water evaporates so quickly it concentrates the undissolved salts which can damage the plants tissues. This is especially true of bore water, some regional areas and South Australia.
It is not desirable to water daily, and if you have the right approach to water-wise gardening, you shouldn’t need to, (well, ok, unless you are establishing new plants in hot weather, then you will need to).
Ideally, you should water your garden deeply and less often. A good soak is much better to as it encourages deep root growth, which helps your plants resist heat stress and reduces their dependence on constant watering.
Water the soil deeply, so that the moisture levels remain even. Where possible always water the soil rather than the leaves.
The roots are where the plants access the water and utilise it for growth and function. Watering the foliage can encourage fungal disease, especially in spring and autumn as the foliage stays wet during the cool of the evening. In hot weather, if you water the foliage in the heat of the day, and the total dissolved salts is high, it can burn the foliage.
1. Deep, regular watering every week to ten days provides consistent moisture to enable the plant roots to grow at a healthy rate and create a strong, disease resistant plant.
2. Watering too much too often – the roots are not proliferating because there is not enough air in the soil to thrive.
3. Shallow, frequent watering encourages the roots to grow at the top of the soil where they are easily damaged and unable to access the stores lower in the soil profile, so less likely to survive dry conditions.
You should aim to apply around 24L per square metre every seven to ten days to keep your plants happy and healthy. Plants absorb water from the root zone which is usually 15-20cm below the soil, so aim to wet this deeply when you water.
This 24L is roughly equal to 24mm of rain. So when you hear the meteorologist tell you there has been 1-2mm of rain for the week, you still need to water, especially if the weather has been warm. The soil might look wet, but if you dig down you will see the rain has just touched the surface. However as the rain has touched the surface, it is a good idea to water, as it will help push the water down into the soil profile.
If the weather has been hot and dry for many weeks, or the soil has dried out, you may need to increase the amount and frequency you are watering in order to re-wet the soil. Re-wetting the soil ultimately uses more water than maintaining a constant watering program.
If you are unsure you are watering your garden enough, get your hands dirty! Dig down into the soil around the roots of your plants and have a look to see if it is moist. If the area around the roots is dry, more water is required. The soil should ideally be moist, and crumbly.
A less invasive, and more obvious way to see if your garden needs more water is to examine the leaves. If you plants have a darkening leaf colour, or wilted foliage it is a sign they require more water. Some plants will wilt before they are stressed and this is a good guide for watering, for others, waiting until the leaves are wilted can be detrimental to the plants as it is a sign of stress.
There are many options available to help us water our gardens, and many opinions ato which are the best methods. The basic rule is that water should be applied around the roots wherever possible, so ideally you should choose a system that delivers water slowly and gently to the soil around the base of your plants.
To enable the water to percolate into the soil profile and not become run off, watering at a slow, at an even pace is best.
A deluge of water could cause the soil to compact, reducing air around the roots, which is important to their survival. For this reason a drip, gentle hose with a shower or spray setting, a mister or watering can is best.
Fixed drip systems or flexible seep hoses are a brilliant choice for efficient watering. If you are creating new garden areas it is a good idea to incorporate a drip system into your ground work. Seep hoses are more easily installed in existing gardens. Mulch can be applied over the top of both to hide them if desired. Attaching them to a timer saves time and labour, in summer you should set it to water in the early evening to avoid water loss through evaporation. Be careful you are not watering to saturation point, you can easily adjust the system to suit the seasonal rainfall. Some systems come complete with rainfall monitors that can do all this for you which is fantastic, especially if you are away on holidays!
Hoses or watering cans can be utilised very effectively, but should be used on a gentle spray rather than a high burst of pressure, which makes this method quite slow and time consuming. However, it can be very therapeutic for the gardener, and spending extra time in the garden you may see early warning signs of pest or disease and cut them off at the pass! If you can afford the time, and your garden isn’t too large, this method is certainly effective.
Sprinklers are a convenient option, particularly for lawns, but there is a risk that they can be forgotten and left to run for hours, which of course leads to massive water waste, you also lose some of the water due to evaporation.
Reticulation systems offer convenience and are very good for watering specific areas. These should be used in conjunction with an automatic timer for maximum efficiency and minimum waste.
Different plants require different amounts of watering. Here is a general guide to how much your plants need:
New plants or seeds that are establishing need to be watered frequently as they are susceptible to water stress. Their roots are only growing in the top few centimetres of soil, so they are unable to access any of the water in the soil profile. For this reason it is best to plant in autumn or spring when natural rainfall occurs to help maintain moisture levels in the soil.
Established perennials have shallow root systems, to only 10-20cm down, so need to be watered before hot dry weather so they can continue to thrive and flower well. Regular applications every week to ten days work well.
Established trees and shrubs have lovely long reaching roots so won’t need to be watered unless there are drought conditions. It takes a tree or shrub up to five years to become established.
Veggie gardens generally should be kept nice and moist, especially if the seed is freshly sown. Adding a thick layer of mulch will help to reduce watering requirements. These plants need the most water when they are fruiting or flowering, the amount depends on the type of vegetable. Leaf crops like lettuce need constant moisture. Root crops such as beetroot and onion need less water. If crops such as tomatoes dry out it can affect their fruit.
The golden rule of reducing water waste in the garden is simple – mulch, mulch, mulch! Organic mulch is absolutely the best method to seal in the moisture and reducing evaporation loss from the soil. The added bonuses are weed control, improving the appearance of your garden, and adding delicious nutrients to your soil. If the ground is dry, water deeply before applying your mulch. A 7-10cm layer is ideal. You can mulch right up to the stem of the plant, just ensure it is low at this point so it doesn’t encourage collar rot – a thin layer, up to 3cm of mulch near the plant stem will remain dry enough not to cause a problem.
When planting new additions to the garden, raise the soil slightly to form a ‘moat’ around the base of the plant as this will help to prevent water run-off and direct it down towards the roots where it is needed.
If you are planting a new garden, or adding a new plant, digging through some well rotted organic matter into the soil to a spades depth or more will help retain water in the soil.
The condition of your soil has a lot to do with how much you need to water. Sandy soils don’t hold water well, and a crust may form on the surface, which can reduce water penetration. Digging through some compost will help water retention and drainage providing a more healthy soil in which your plants can grow.
In clay soils the opposite is true as the soil holds the water too well and drainage can be an issue. Heavy clay soils will require the addition of some coarse sand. Just adding organic matter will not be enough to improve drainage, and it will break down too quickly. Another alternative for heavy clay soils is to grow your plants in raised beds.
Sandy soils have sharp drainage so are unable to hold water around the roots, therefore they should be watered more often.
Heavy clay soils can be watered with less frequency as they hold water well with the finer pores of their soil structure.
Dig out any weeds, they suck moisture from the soil that your plants could be utilising.
Adding a dry tolerant ground cover to your soil can act as a living mulch and help to keep your plant roots cool.
So, to sum up, you want to water your garden deeply on a weekly basis in dry weather. Water is most effective when applied gently to the soil around the roots, and in a cool part of the day.