How mulch keeps your soil cool and cuts your summer watering

How a layer of mulch keeps your garden going through a dry summer

If you have ever stood out in the garden on a hot afternoon watching the soil crack open while the plants wilt, the problem is probably not how much you are watering, it is where that water is going. Bare soil in full sun heats up like a driveway, and a fair bit of what you hose on in the morning has gone into the air before the roots ever get a look at it.

Mulch is the fix, and it is about the cheapest and least skilled job in the whole garden. You tip it on once and it keeps working for months.

What mulch is actually doing down there

It shades the soil, so the ground stays cooler and holds onto the water you put on it instead of handing it straight back to the sky. It keeps the weeds down, because most weed seeds need light to get going and they are not getting any under a decent layer. And the organic mulches feed the soil while they break down, which is why a bed that has been mulched a few years running is so much easier to get a fork into than one that has been left bare.

The one people do not think about is the temperature swing. We get cold nights followed by properly hot days here, and roots sitting in bare soil cop the whole of that every day. Under mulch they do not.

Which mulch to use

The best one is the one you will actually go and get, but they do behave differently, so it is worth knowing which is which.

• Pea straw is soft, breaks down fairly quickly and adds nitrogen while it goes, so it suits veggie beds and roses. It will sprout the odd pea and that has never bothered anyone.
• Sugar cane is light and easy to spread, and it is the one I would reach for over a big bed, because you can shift a bale on your own without doing your back in.
• Composted mulch like Whoflungdung is heavier, so it stays put when it blows a gale, and it conditions the bed underneath while it sits there.
• Bark and wood chip lasts the longest, so it suits natives, borders and anywhere you would rather not be topping up twice a year.

The one to steer clear of is anything really fine, sawdust especially, because it mats down into a crust that sheds water rather than letting it through, which is the exact opposite of what you were after.

How to spread it without wasting it

1. Weed first. If you skip this the weeds just push up through and you are back out there in a fortnight wondering what went wrong.
2. Water the bed properly before you mulch. Mulch holds moisture in, so if the soil is bone dry underneath you have just locked the dryness in.
3. Go 5 to 7 centimetres deep, and keep a clear ring around stems and trunks so nothing is sitting damp against the bark and rotting.
4. Have a look at it every few months. Organic mulch is meant to break down, so when it goes thin and patchy you top it up rather than starting again.

What changes once it is on

A bed that used to want water every second day will usually stretch out well past that once it is mulched, and on the days you are watching the tank level that is worth more than any gadget you can buy. You also get fewer weeds, better soil underneath and roots that are not being cooked and chilled by turns.

It is not a flash job and nobody is going to compliment you on it. It just quietly works, which is my favourite kind of gardening.

Shop related products

• Easy Wetta Garden Mulch 50L. Bagged mulch for beds and borders, easy to carry and easy to spread.
• Martins Organic Sugar Cane Bale 11KG. Light bale mulch that covers a big area for what it weighs.
• Martins Organic Pea Straw Mulch 11Kg. Soft mulch for veggie beds and roses that feeds the soil as it breaks down.
• Neutrog Whoflungdung Mulch 20kg. Composted mulch that stays put in the wind and conditions the bed underneath.
• Brunnings Garden Compost with Seaweed 25L. Dig this through the bed first, then mulch over the top of it.

The whole lot is in the garden centre at the shop, and there is more of it in the garden range online. If you would rather not fit bales in the car, we deliver on Tuesdays and Thursdays on anything bought from us, $5 around Strathalbyn and $10 on the regional run. Local delivery.

Read next

• Setting up dripper irrigation, a beginner's guide
• What is the cardboard weed barrier method?
• How to care for your flower beds during scorching summers

Mulch is the one garden job where doing less actually works, which suits me perfectly.

Candeece

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