Making a mess with mulch

I've killed several trees with well-intentioned mulch, like the young grapefruit trees that I surrounded with old carpet, to keep the weeds down and the moisture in. The carpet did both perfectly.

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Not a single weed came up through it — and not a single drop of rain penetrated the carpet to water the trees either. By the time I realised that the carpet was backed with waterproofing, one tree was dead and the others none too healthy, either.

Even a loose mulch of autumn leaves and lucerne can soak up the small amounts of rain we usually get in droughts. Two to three millimetres in a night once a week can be enough to keep plants alive, but if the trees are mulched, even with the best mulch possible, the mulch will soak up the rain shower long before the water reaches the plant roots.

It took me years in the ‘90s drought to realise that the Tahitian lime trees I'd mulched with decayed wood chips weren't doing well. They needed extra tucker — wood chips are low in nitrogen and were using up plant tucker as they broke down. The vegie garden mulched with well-broken-down, composted wood chips was even worse. Seedlings just seemed to vanish when I planted them in the compost-rich soil. The “composting” was killing my seedlings to turn them back into soil.