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  4. Module 22: Watering & Irrigation Systems
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  3. Module 22: Watering & Irrigation Systems

Module 22: Watering & Irrigation Systems

One important aspect of gardening is watering your plants correctly. Knowing when to water, how much to water, and the factors that affect watering can make a big difference in the health and growth of your plants. In this lesson, we will cover these topics and also provide an activity to make your own water butt for storing rainwater.

Lesson Objectives

  • Understand when to water your plants and the best time of day for watering
  • Learn how much to water your plants and how often to water
  • Identify the factors that affect watering, such as soil type and weather conditions
  • Recognise the signs that your plants need watering
  • Understand the benefits of using rainwater and learn how to make your own water butt

Watering your plants

When to water

The best time to water is in the mornings when the sun is just starting to come up and plants will start to use water. The soil surface and foliage is also more likely to stay drier for longer then evening watering. This discourages snails, slugs and mildew diseases. Evening watering is also fine, so long as the weather is not too warm, less water is lost to evaporation. You should never water when it is hot in the middle of the day as most of the water will be lost through evaporation from the soil’s surface.

How much to water

The amount of water required will largely be determined by the plant’s water requirements and its rate of growth. The sort of soil, as well as climate, are likewise significant factors.

Light sandy or chalk soils require more frequent watering than heavy clay soils, but less water can be applied each time because excess water will easily drain away. Due to more water within their structure, heavier, clay-based soils require heavier water applications but can be watered less frequently.

Try giving container-grown plants 10 percent of its volume in water each time you water it. Therefore, add 1 litre of water to a 10-liter patio pot. Slowly pour it on, trying to keep it in the pot and prevent it from draining out of the bottom. Any leftovers can be reabsorbed by catching them in a saucer under the pot. After watering small containers, gently lift the pot to check for weight and, if not, add a little more water. When the pots are empty and need water, you can soon tell how light they are.

Watering frequecy

Each plant has unique requirements, so there is no one-size-fits-all formula for watering. For instance, a container plant may require daily watering in hot, sunny weather, whereas a mature shrub may only require a drink in extreme drought. Keep in mind that if more water is given to plants, they will need more water. You can let them dry out a little between waterings and they won’t need to be wet constantly.

Factors that affect watering

  • The larger the plant is, the more water it is likely to lose and the more nutrients are needed to flower. This is the same for plants with lots of foliage.
  • The compaction, texture and structure of the soil it is growing in also has a big impact on the amount of water needed. Clay soils can hold more water than sandy soils, but plants extract water from sandy soils better.
  • Compared to a border plant, a large plant in a small pot will require more frequent watering. The roots in a border are free to grow wherever they can find water, drawing moisture from a significantly larger volume of soil than in a pot. Pot-bound plants dry out especially quickly.
  • Precipitation, long stretches of daylight, temperature, wind and dampness will influence the pace of water utilised. In general, plants require more water during the warmer months of the summer and less during the cooler months of the winter. Additionally, they will use more in hot, sunny, and windy weather.

Signs your plants need watering

If you notice any of the following signs, it may be time to water your plants:

  1. The foliage is growing slower than usual or not producing fruit or flowers.
  2. Leaves or stems may look dull, dark, or pale compared to their usual shiny appearance.
  3. The position of leaves may change, angling downwards or curling.
  4. The pots feel lighter, and they may blow over in the wind.
  5. Powdery mildew appears on the plant.

Remember that the soil or compost surface may not always indicate whether the plant needs water. Using the touch test, it’s best to check the soil moisture at the root level. Stick your finger into the soil to a depth of about an inch. If it feels dry at that depth, it’s time to water your plant.

Sources of water

Rainwater is a great plant option and the first “go-to” for gardeners because it is free and can be stored. It takes energy and treatment to deliver tap water to our homes, and it may contain more minerals than many plants require.


A step-by-step guide to making your own water butt

Over recent years we have had some intense summer heat, which has often lead to a hosepipe ban. Unfortunately for gardeners, this can stop may plants from getting the water they need. Luckily, with enough planning in advance, we can fill up water butts with rain water and store it for the summer. Follow these simple steps to creating your own water butt:

  1. Find a large container (an old plastic bin with a lid or wooden barrel works well) and a location to place it. We suggest placing your water butt near a downpipe of your guttering or in a location that is open to more rainfall.
  2. Drill a hole in the side of the container, a few inches from the bottom. Use this hole to add a tap or drain valve to empty out the water as needed. (You can also drill a small hole at the top of the barrel to allow some air to flow in and out of the container.)
  3. Make a base to raise the container off the ground using bricks, wood or something equally sturdy. It is best to raise it high enough off the ground to fit a bucket or watering can underneath the tap at the base of the container.
  4. Place the barrel on the base, and direct the downpipe into the container.
  5. Cover the top of the container with a lid to keep any debris, such as leaves or dirt, from entering the container. A mesh cover will keep out most debris if you do not have a suitable lid.

Irrigation Systems

Drip irrigation is a slow and controlled watering system that uses small emitters to deliver water directly to plant roots. It prevents overwatering and conserves water by giving plants only what they need. It works by allowing water to slowly seep into the soil, which is more efficient than traditional sprinkler systems.

Drip irrigation is suitable for most types of gardens and adapts to irregularly shaped and uneven slopes. It is especially useful for raised beds, row crops, and trees. The amount of water used depends on various factors, but on average, it uses 2L to 20L of water per hour.

Drip irrigation is more efficient, cost-effective, and eco-friendly than spray or sprinkler irrigation systems. It delivers water gently and precisely, preventing damage to delicate plants and crops.

Coming Next

Watering your plants is vital to gardening, and understanding the right techniques can help your garden thrive. By knowing when to water, how much to water, and the factors affecting watering, you can ensure your plants get the right amount of moisture. And by using rainwater, you can save money and help the environment. Following the tips in this lesson and making your own water butt, you can take a big step towards a healthy and sustainable garden.

Updated on March 5, 2024

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