I’m not gonna beat around the westringea here. You know that black mulch that costs more than any other? The stuff you see hastily piled into garden beds when a house goes on the market? Well, it’s crap.
Black mulchies will be taking on combat stances at this point. People don’t like having their assumptions challenged. Like, black mulch must be the best. It looks so dark and rich and fertile, and the pro gardeners use it, and the soil and garden centres recommend it, and it’s expensive.
That last point’s the clincher. Quality usually is directly proportional to price. You get what you pay for, right?
Right, but wrong in the case of mulch! Wrong wrong wrong!
In fact, the best all-purpose* mulch you can get is sourced from green street tree prunings – and it’s free! Or can be. Go directly to www.mulchnet.com. You don’t even have to tell them I sent you.
*Note: Green tree prunings mulch can be used on vegetable gardens, but not by itself. Put a layer of pea straw or similar down first.
So, WHY is black mulch bad and green tree prunings mulch good?
In answering that, it makes sense to first consider the purposes of mulch:
- To prevent evaporation of water from the soil underneath, thereby keeping moisture available for plants and minimising water waste.
- To insulate the soil surface from temperature extremes. In Perth, it’s especially important to keep soil cool in the withering heat of summer, so surface roots of plants are not damaged, earthworms are not driven away, and beneficial microbes and bacteria are preserved.
- To assist in maintaining water absorption properties of the soil (as any Perth gardener knows, our sandy soils are notoriously hydrophobic; hence the proliferation of wetting agent products on the market – Ezi-wet, Grosorb, Riversafe, Proganics etc).
Green tree prunings mulch, used properly – which means spread 10cm (4 inches) thick – gets a big tick for numbers 1, 2 and 3. I can vouch for that, having used it exclusively for almost 5 years now.
Green tree prunings mulch is coarse and the water runs straight through to the soil below. Scrape some away in the heat of a summer’s day and you’ll find the soil underneath moist and cool. You never need to treat the soil with a wetting agent.
By contrast, black mulch is soft and spongy and absorbs water. This runs contrary to its purpose as a mulch by denying water to the soil beneath! You need to saturate it to get water through to the plant roots, and as it dries out it soaks up water from wherever it can get it – that is, from the soil! The story gets worse. In time, black mulch becomes hydrophobic! Yes, it repels water. Further, since it’s black, it absorbs heat from the sun. That ain’t keeping your soil cool!
Aside from not fulfilling its basic functions as a mulch, black mulch is not eco-friendly. “Top quality” (ie: expensive) black mulch contains peat, a non-renewable resource that is mined from natural wetlands in Perth and the South-West. Extraction of peat on a commercial scale permanently degrades or even destroys these wetlands. Don’t take my word for it – consult the experts. There is plenty of info on this online. If you’re an advocate of sustainable gardening practices – which I am – peat is off the menu. Another strike against black mulch.
Finally, the cheaper black mulches are dyed black – occasionally a retailer will be honest enough to acknowledge this (see www.cfulton.com.au). In some instances, the dyes used are petroleum-based. BAD for your garden. BAD for the environment.
That leaves black mulch with one redeeming quality – it looks good. (Actually, I reckon it looks shite – I far prefer the natural look of green tree prunings mulch…but let’s go with the general consensus for now). But for how long does it stay dark and moist and rich-looking? Anyone who has used it will be aware that it becomes bleached and desiccated within a few short weeks of exposure to summer sun. How attractive is it then? Huh?
Green tree prunings mulch also weathers in the sun, but retains its natural look. Aesthetically, I think it’s very much in harmony with natives and waterwise gardens. If you’re stuck on the traditional Euro look – fastidiously manicured close-cut lawn, camelias, gardenias, azaleas, cottage garden annuals etc – you’ll probably struggle to tune in to my perspective. But there’s a remedy!
Book into your nearest Great Gardens seminar, and attend with an open mind. These guys are experts at the cutting edge of waterwise, sustainable gardening in WA. They have recognised that conditions in Perth and regional areas of WA are unique, and that gardening strategies that work in the Eastern States – and/or the northern hemisphere – do not necessarily work here. And the alternative strategies they advocate DO work!
The Great Gardens crew includes well-known identities such as Josh Byrne, Sabrina Hahn and John Colwill, but their credibility has nothing to do with celebrity. In fact, the GG speakers I find most rivetting and inspiring – Chris Ferreira and Peter Coppin (ex CSIRO horticulturalist, specialising in fruit, vine and nut crops) – do not have a media profile.
Quite simply, all the GG crew know their stuff, and put the theory into practice in their individual landscaping and gardening businesses and projects. They are part of a larger network of specialists like Peter Cundall and Jerry Coleby-Williams who are committed to sustainable gardening practices that are environmentally friendly AND mindful of aesthetics (if you like neat cottage gardens, the new breed of natives and waterwise plants will fill the bill at least as well as yer trad Euro plants).
And me? I’m no expert, but I’m now a lot better informed than many of the good but misguided folk whose hopelessly displaced, water-guzzling, fertiliser-dependent, Euro-style gardens I walk past daily. That is not a boast. I am merely well-educated in waterwise and sustainable gardening practices, largely thanks to the Great Gardens seminars. And I have learnt a lot through practising what the GG crew preach over the last 5 years.
This mulch stuff I’m banging on about is not just theory or opinion. It’s borne out in practice. Since I got on to green tree prunings mulch back in 2004, weeds have been minimal, the drip irrigation does its job silently under the mulch, delivering water directly to the roots of the plants without losing a drop to evaporation…and yes, our water bills are less. Dig under the mulch and you find that it has broken down into a lovely dark, rich, moist compost riddled with earthworms.
The only downer is that it is now – 5 years down the track – time to top it up. Too much of it has composted, and the weeds are starting to come back. Oh yeah, and the word is out about Mulchnet – you can wait a while for free mulch these days. Bummer. Then again, there is always the option to jump the queue and pay for it! And it’s a lot cheaper than that black crap (or “for sale mulch”, as I heard it referred to recently).
Economically, environmentally and horticultually, green tree prunings mulch is out on its own.
If you’re a black mulchie, now you know better. But if you’re still not convinced, get ye to a Great Gardens seminar. It takes a leap of faith to let go of your assumptions and traditional ‘wisdom’ and adopt a whole new approach, but I promise you, the rewards are great. And once you take the plunge, you find your perception permanently altered. There is no going back. Why on earth would you?
PS: I became aware some time after publishing this post that there is a small risk that mulch from green tree prunings can carry dieback. Responsible tree pruners minimise this risk by appropriately disposing of prunings from infected trees. However, human error must be factored into the equation, so be aware that the risk does exist. Realistically, though, the chances of copping a dieback infected load of green tree prunings mulch is very small, and can be easily managed. Sabrina Hahn, acclaimed Perth environmentalist, gardening educator, landscaper and horticulturalist specialising in native Australian and Mediterranean plants, neatly sums up the situation as follows:
UPDATE, August 4th 2011:
After 8 terrifically productive years of cutting edge seminars on Perth and WA-specific sustainable gardening, the Great Gardens team has split into two groups – Great Gardens and Beyond Gardens. Both are continuing with the free waterwise gardening seminars. Seminar dates and locales are now available on their respective websites. Booking essential.