The Gordon Gnohm

Play along at home, read Future Farmer in The Braidwood Bugle every Wednesday. 

Mulch Pt 3

The key to your soil health is living thriving microbes. Like all livestock, microbes need to be nurtured, sheltered and they need to be fed, a lot. High quality feed usually grows better beasts and so it is with microbes. You get out what you put in. 

Mulches can be beneficial, or they can be detrimental to your garden. Make educated choices and your gardening will be easier, faster and more enjoyable.

Mulch to avoid

White Pebbles

Please don’t use them! The look of the white will fade very quickly as debris collects in the gaps. Organic matter is not white, so even the smallest amount will stand out. If you have too much time on your hands or you dislike your gardener this might be the mulch for you. 

If you do have a gardener, it will cost a lot to keep the white pebbles clean.

I have a friend who builds landscapes ‘opposite to my natural ones’ as he says. Some people like the white pebble look so much, he replaces it biannually to maintain the effect.

Tan Bark

A lot of mulches contain tanbark. Do not accept mulch containing tan bark. This mulch will not assist your gardening endeavours. A plentiful by product from pine plantations, so it’s understandable that it makes its way into some landscape centres. Best specified for soft landings in playgrounds, but a terrible mulch for gardens. 

Tan bark lasts a long time and that makes people happy. When the rest of the mulch is consumed the tan bark is all that’s left. It seems like good value, so how can it be bad?

If you look at a chip of tan bark closely, it is very porous, with many layers and air gaps. The bark chips are like little sponges, absorbing water from the active soil underneath. The chip then releases this moisture into the air as the sun bakes each bark chip. There is no way to hold water in your soil with this covering. Please check with your woody mulch supplier to see if their offerings contain Tan Bark. If so, find a new supplier.


A few years back I used straw bedding to mulch with. It was cheap and plentiful, so I bought a truck load. It was easy to handle and spread. It looked great on the garden, but it was a big mistake! 

The hollow centre of the straw was a great place for pesky mites to live and thrive. The straw also acted like a sponge, transferring water from the soil to the air. Luckily there was a lot of skywater that year. 

The worst of it was creating habitat for slugs to breed and decimate anything growing nearby. The straw didn’t compact under its own weight, so it was always airy and provided perfect tunnels for slugs to pop up at the base of plants, and just start munching, sometimes even when the sun was out.

Since then, I have read in a ye olde homesteading journal, not to use straw on the garden for the same reason, slug habitat. Straw is good for putting in bog holes, short of that I have no use for it in my garden.

Plastic Mulch

Black plastic mulches used by market gardeners, farmers and landscapers are not a good option if you are caring for your soil health. They starve the soil of oxygen, killing beneficial aerobic microbes. Plastic mulch also prevents skywater entering your soil. Exposed to the sun, the soil heats up and bakes the seeds underneath. 

Microbes will die above 65C+. Most seed is exterminated around 60C. It’s a fine line. So, if the black plastic lays down all summer the microbe death will be significant as will the work to remediate the baked earth underneath. 

Pasture Hay

A major benefit for you and your property, but probably not in your garden. If used on your garden, the risk of seed strike is high. Taking the weed sprouts out will take time and possibly ruin your gardening pleasure. 

I have used it in a Permablitz situation, where the client purchased the ‘cheap hay’ rather than lucerne, not understanding the difference. It went down under woody mulch. Thinly mulched spots promoted seed strike and a whole summer, and winter, were spent weeding. Every new planting released more seeds to the surface.

This common mistake offers us great learning. Avoid pasture hay in your garden and think about introducing it into your paddocks instead. The seed load from another farms paddock can improve your paddock with ease. 

Introduce pasture hay into damp spots or shady spots, the animals will trample it in as they eat. Remove the animals and let it grow. You will find new shoots appear in weeks and the microbes will appreciate the raw material. I do this for our chickens and will do it when I get into 4 legged soil improvers too.  

This week

If you built a Weed Free Veggie Bed, you may notice some pixie mushrooms popping up after the rain. A good indicator that life exists. They look like they came from a Tim Burton movie, they are nontoxic and an essential part of healthy soil life.

All 10 Tomatoes are in flower! They are 30cm tall after planting them deep. The cold front hasn’t bothered them at all. The plants are too big to box now. Wild grown tomatoes for the win. I avoid greenhouse tomatoes in the highlands, they really don’t perform well in the cold snaps. 

Pumpkins and zucchinis are setting flower but growing slowly as the soil temp has dropped to 17C, the skywater sitting in the soil, the hail and the cold front passing through. Soil temp will rise quickly again this week with reasonable nights and sunny days. 

This is a very, very early summer season, as indicated by the cabbage going to seed, along with the carrots, beetroot, spinach and parsnips. We are usually starting to feast on these crops, but the heat arrived early this year. So now we plant summer vegetables and wait to collect seed and its only October.  

Potatoes are popping through the mulch, last years spot is producing again too. There are always stray spuds left behind but eat these ones early while the main crop matures. Onions have been planted near tomatoes. Summer lettuce in between onions. I planted Lucerne seedlings into the centre of each veggie bed as living mulch and to bring up nutrients from deep below. 

What can you do to keep your soil healthy in your paddocks?

Next week living mulch.

Stay Awesome

The Gordon Gnohm

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