Conscious Gardening

time. These mulches are ideal for ornamental trees and large shrubs. Of these mulches, sawdust needs a further explanation.

SAWDUST: First and foremost, the older and more decayed the sawdust you use, the better. Sawdust is extremely dense and can become compacted after even moderate rainfall. During a dry spell, if a heavy shower dropped 25 mm (1 in) of rain in your garden onto a mulch 150 mm (6 ins) deep in sawdust, it is doubtful that a single drop would penetrate far enough to reach the soil; the sawdust would absorb all the rain. A thick sawdust mulch in these conditions is not a good choice. However, if that sawdust was mixed in equal parts with very coarse wood shavings, or bark, then the rain is far more likely to percolate down to the soil. For reasons like this, it is important that you are familiar with your climatic conditions, and with what mulch you need to use, and why.

Depth of mulch also has to be considered with cover mulches. You need only use 60 mm (2-3 in) of sawdust to act as a long-term mulch in a shrubbery. Its very density acts as a good insulator, and a thinner layer would allow for rain penetration. However, if you went for the more popular chipped pine bark, then at least 150 mm (6 in) in depth would be required.

It is open and coarse, so rain can easily trickle through pine bark, but, almost as easily, moisture can evaporate back up through it.

FEEDER MULCH: There are many places in the garden where coarse, or slow to decay, mulches are totally unsuitable. Unlike a cover mulch, feeder mulches are chosen to breakdown reasonably quickly, thus feeding the soil life and promoting rapid fertility while also offering soil protection and smothering weed germination and growth. Again, check the CN ratio to see why this is so. One of the very best feeder mulches is alfalfa (lucerne) hay, but any old hay is excellent. Most hay has plenty of nitrogen rich plants in it, such as clover and trefoil, the more the better.

I recommend a feeder mulch for all vegetable gardens, flower beds, roses - they love mushroom compost - all berry and small fruits, and, in fact, most fruit trees. Very large fruit trees, such as mature mango trees or mature macadamia nut, would certainly benefit, but it would be expensive to cover that amount of root system. If you have several trees like this a load of sawdust spread under them would be beneficial, with a few buckets of blood and bone added.

Straw is an excellent feeder mulch. It matters not whether it is wheat, barley, oats or rice; it is all very good. It is slower to break down than hay, but with grass clippings mixed in, the decay can be speeded up.

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