climateXchange

Hi Marea,

Mulch, I'm topping up my garden now. The last time I mulched in a big way was about 2005.

Depth – I've seen different references to depth, usually 5 to 7cm seems to be the average. Less than this and it can be ineffectual. Equally, however, you don't want to put too much on because it can prevent water from percolating into the soil. Also, heed the warnings that mulch should not be placed all the way up to the trunks of plants.

Types - Here's what I've deduced from my own experience, which has confirmed what is widely written in good gardening books and the internet on the subject.

1. Don't buy the expensive eucy chips, or any chips which are all homogenous in size. The stuff might look good, but it agglomerates, sticks together and prevents water from getting through. Trust me, I made the mistake of buying 15m3 of this stuff and it's taken years to rot down and I've had to go out and break the stuff up manually this spring so I can top up with other stuff. 

2. It's cheaper and it's better to get the 'forest mix' or 'slash'. The latter two are a mixture of different types of bark/wood strips of differing sizes, this means it's less likely to stick together and it will allow water through. If you live south side and want a lot of the stuff, ring up Corkhills and order a truck load. I recommend everyone go have a look at their nearest tip/recycler if they've never done it, it's quite uplifting to see all the green waste people drop off converted into mulch in Canberra. 

3. Mulch doesn't have to last forever. Personally, I'm a huge fan of mulch which degrades within 18 months, but the stuff I favour can't be bought for love or money at the moment. For roses, veggies and fruiting plants people often prefer lucerne or pea straw, because it's high in nitrogen and enriches the soil. Similarly, 'green mulches' are ones you grow yourself and till into the soil. I tried using sugar cane mulch, but I don't think it has the nutritive value of lucerne or pea straw, although it breaks down well enough for veggie garden use. 

4. The type of mulch will have a certain acidity or alkilinity (Ph) that you have to consider based on the type of plants you want to grow. Pine bark, for example, is acidic. Some exotic plants like acidic soil. Native plants often don't. It's worthwhile checking out the Ph of your soil. If your plants are growing well in it, most likely you want a mulch that will have a neutral effect on the Ph. 

5. Wood based mulches can 'denitrify' the soil, that is as they break down they take nitrogen out of the soil. This is a temporary effect. You might want to compensate with a bit of fertiliser, sometimes the pre-packaged mulch has fertiliser in it for this purpose.

6. Expensive is not necessarily best! When I landscaped my nature strip some 6 years ago, I used the cheapest materials and tubestock I could buy. I mulched with layers of newspaper, under wood chip. Under my photinia hedges, I layer mulched using the leaf fall from my street trees, under wood chip. During the drought, I watered with laundry rinse from my washing machine. In both cases, the plants on the verge and the hedge took off in an unexpected way, they grew more luxuriously even than the plants in the garden proper which had been put into imported top soil and mulched with the more expensive eucy chip! So, thin layers of newspaper (2-3 pages max) wetted and laid under some soil or other mulch will break down and can form an excellent mulch. I've just layer mulched with the leaf fall from the oak and plane tree outside again, having checked on the leaf mould formed from the same about 2 years ago. Both are free and work like a dream.

For most gardening issues in Canberra, I rely on "The Canberra Gardener" published by the Horticultural Society of Canberra. I also highly recommend Kevin Walsh's book "Waterwise Gardening", but there are different books on similar materials, including excellent materials for free on the internet. 

Last weekend I went out to Corkhill's in Mugga Lane and, as you mentioned in your post, Quetzal, there was a long line of cars with trailers full of green waste waiting to drop it off. It was indeed uplifting to know that it will all be converted into great compost and mulch.

I ordered a pile of the course forest litter and have been spending a few hours most evenings this work laying down this mulch on the garden. I'm still only half way through!!

Following advice from the ACT Government waterwise person who came round a few weeks ago to do a free assessment (a good service for people to use if they haven't done so already), I also created a gravel ditch along the drip line of some thirsty trees that I can use to get water closer to their roots in dry conditions. Hopefully this will dissuade them from sucking dry the adjacent mulched areas where little plants are struggling to compete. One can always hope!

Anyway, a trip out to Mugga Lane is interesting for anyone wanting to know what happens to all your waste and recyclables.