Rules of Watering Plants 

Plants Need Water

All plants need water, but their requirements vary considerably depending on the plant. E.g. cactus can survive long periods of drought because they store water and are structured to be able to reduce water loss, while young annual plants from temperate regions have evolved to 'expect' moist soils and cool conditions, where water loss can be easily replenished.

Where Do Plants Get Water?

The vast majority of plants get their water from the ground and have root systems that thread through the soil particles to absorb water and nutrients. The water is then moved up through vessels (xylem) to the rest of the plant.

Some plants can absorb water through leaves and some do not live in soils; living on another plant, parasitising it by taking water and nutrients from the host plant. But it is likely that all the plants in your garden have roots in the soil for absorbing water.

When to Water?

Think about the plants and what their needs are. Feel the soil; feel the soil below the surface where the roots are. The surface may be dry but deeper down there is water available to the plant roots and it may not be necessary to water the plants. Conversely, the surface can be wet, e.g. after a light shower or settled dew, but the soil down where the roots are is dry. In this case, the plants do need to be watered.

Too Much or Too Little?

Plants can have too much water as well as too little. Over-watering can cause symptoms similar to drought; e.g. wilting and yellowing of leaves, because if the roots are in saturated soil for long periods they cannot absorb oxygen or take up nutrients.

Too much water can also encourage diseases such as root rot and Phytophthora.

Tips for Watering Your Garden Plants

• Diseases thrive on wet foliage and spores can be distributed by water splashes; water the soil and where possible avoid wetting the leaves.
• If the soil is very dry it can be water repellent on the surface and the water will run off rather than soaking into where the roots are; water slowly so that the water has time to wet the soil and move down to the roots.
• Improve the drainage around the plant by ensuring the soil is not compacted around the roots; gently fork the soil around the roots to ensure the soil is able to take up the water and oxygen from the air. Take care not to damage the roots.
• In general, you want to encourage the plant roots to grow deep in the soil so the plants are better able to withstand drought. Soils can hold a lot of water and it can take time for the water to seep deep down to the lower roots. Water evaporates off from the surface so deep water is available longer; water thoroughly occasionally rather than a little frequently. This gets the water deep in the soil and the plant roots seek this water out by growing deep.
• How much water will the lawn soil hold? - Sandy soils will hold approximately 25 L/m2, clay soils will hold approximately 3 times as much but it will take longer to seep into the soil.

Tips for Watering Your Lawn

• As above, encourage grass roots to grow deep by thoroughly watering the soil occasionally rather than wetting the lawn frequently. Good grass root depth is approximately 15 cm.
• Grasses are susceptible to disease such as red thread, greasy spot and brown patch. These diseases thrive in warm wet grass, so water thoroughly 1-2 times per week rather than a little every day.
• Deep watering once per week will probably take 2 – 3 hours allowing the water to slowly soak down deep into the soil.
• Water early in the morning or late in the day.

Tips for Watering Your House Plants

• Research your plant's needs; there is often advice on the label of newly purchased plants.
• Check the moisture of the soil in the pot with your finger or use a Gro-Sure Houseplant Watering Indicator, if it feels moist or the indicator shows blue, do not water, if it is very dry and your finger cannot penetrate the surface, water.
• Few plants like to be in very wet soil for long; water the soil in the pot, or add water to the tray the pot is sitting in so that the water is drawn up into the soil from below (pour any excess water in the tray off if it has not been drawn up within 2 hours).
• Ensure your plants are in pots that allow excess water to drain away. Do not let pots sit in pools of water for more than a couple of hours.
• Indoors is often a very dry environment, particularly if you have air conditioning; many plants will appreciate misting of leaves with water occasionally but do not have leaves frequently wet as this encourages disease. Use Gro-Sure Houseplant Mist'n'Feed 1-2 times a week.
• Use water at room temperature; do not use water from the hot tap.

Happy gardening and growing.

David Brittain
Kiwicare