Drop by drop: Measuring it out

measured_irrigation

Robyn Deed talks to Gardening Australia’s Sophie Thomson about her measured approach to watering in Adelaide’s challenging dry climate.

Sophie Thomson is not a fan of hand watering, in general: “No one does it deeply enough—often you’d need to stand there with the hose on each plant for 20 minutes to do it properly.” She sees many trees and shrubs in water stress due to hand watering. “Hand watering can work well for pot plants and vegies, but not for the general garden.”

More water, less often

To get the required level of watering for trees and shrubs, she’s a fan of low-pressure sprinklers (for example, Lo-Flo an Australian invention, WaterMark approved), which produce big drops rather than mist, or drip irrigation systems that can be turned on for the required period. The watering system might need to be on two hours once a fortnight to get the deep good soak the plants need—more water, less often is the mantra.

But how do you know how much water is needed? Sophie advises that the best way is to look at what you’re doing now and adjust from that. “Start by watering as you normally do and then dig down next to the plant to see how deep the water has gone; it will often be just a couple of centimetres, but trees and shrubs need the water at their root zone, 20 to 30 cm down.” Adjust the watering time and volume to do this and so encourage strong deep roots.

Read your plants

“You also need to read your plants,” Sophie says. Watering needs will vary depending on such things as rainfall, heat, humidity, soil type and root competition. You can “read” the leaves, for example, as these are a plant’s ‘air conditioning’ system. With citrus, you can feel the leaf on a hot day and, if it isn’t cool to touch, then the plant is too dry; the leaves should also be vibrant and shiny. With vegies, it’s slightly different—”We need to acknowledge that many soft, tender vegies are being grown outside of their climate zone, so we need to accept a bit of wilt in the heat, so long as they pick up overnight and when watered.”

Read the full article in ReNew 135.

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