Compost: The other black gold

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7 • POSTED ON March 28, 2005
Compost: The other black gold
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The key to successful gardening is good garden soil. Pamper your soil and it will reward you with healthy, beautiful plants. It"s that simple.

Our gardening column is published every Tuesday on OttawaStart.

As established in least week's column, the key to successful gardening is good garden soil. Pamper your soil and it will reward you with healthy, beautiful plants. It"s that simple.

One of the easiest - and certainly cheapest – ways to go about improving your garden’s soil is to add "home-made” compost. For the price of 6 bags of compost you can buy your own compost bin, or if you can – accurately – swing a hammer, you can even build your own and save yourself even more money. How you go about it depends on the amount of time you are able or willing to spend. A trip to “Canadian Tire” to pick up a manufactured bin will obviously take less time than building your own, but the hands-on approach will allow you to create a custom designed bin that will fit the one under-utilized corner we all have in our gardens. There is all sorts of information available regarding how to build your own compost bin; look in gardening books, magazines and on the Internet.

First things first; what do we need to know about a compost bin? What does it do and how can we ensure ourselves of fast, odour-free decomposition that will not spoil the neighbours’ garden parties?

Composting is the natural decomposition of organic (plant-related) materials. Walk though a forest in springtime and you will see fallen leaves from last autumn slowly decomposing, thus returning nutrients to the trees. Key factors in this process are air, heat, moisture, micro-organisms and – of course – organic materials. A visit to the City of Ottawa’s “Trail Waste Facility” on Trail Road in Nepean, just off Moodie Drive (south of Fallowfield Road) offers you interesting insight into what decomposing entails. Garden waste, collected by the City from your curb in summer, is mixed – bigger items such as tree branches are shredded - and piled up in huge amounts and left to the elements. When you take a look at the individual piles, you will notice the different stages of decomposing. In fresh piles you can still “recognize” leaves, twigs and stems, but the older the piles are, the more you will see the debris being broken down, eventually resulting in beautiful, rich compost. You can buy compost on the spot, but why pay money to buy back your own garden waste when you can make your own?

It goes without saying that with the quantities of waste the City has to deal with, it is impossible to speed up the process any more than they already do. However, in our gardens, where we deal with much more modest quantities of waste, we can – to a certain extent - control natural conditions by using a compost bin. Designed to speed up the natural process of decomposing, a compost bin will help turn waste into valuable organic matter within a few months, provided it is situated in a suitable spot and treated properly. For obvious reasons, we do not want the compost bin to become our garden’s main feature. Instead, try to find an unobtrusive spot but be sure to avoid putting the bin in a closed-in, heavily shaded area.

Bacteria – the most numerous and effective compost makers - are the first ones to break down plant tissue. Later in the cycle they are joined by fungi, beetles, centipedes, millipedes and worms. In order to do their job properly these creatures – however little they are - need air and moisture (which is why the compost bin should not be placed in a closed-in area). The best way to ensure there is enough air inside the bin is to add different types of waste in layers. For example, filling your bin with too much damp grass cuttings will “squeeze” all air out of the bin, thus creating perfect conditions for so-called anaerobic bacteria. This group of bacteria can live without the presence of oxygen but will turn your grass clippings into a slimy green substance - useless for the garden. Instead, the container itself should have sufficient air circulation and we should make sure never to let the compost material pack down solid. To prevent this, mix fine material (such as grass cuttings) with larger waste (or even shredded newspaper and straw).

As mentioned above, apart from air, water is an essential ingredient. Generally, there will be enough moisture in the green materials you add to the bin, especially if you use grass clippings. However, in a hot summer it is possible that the edges dry out, in which case you will have to add moisture. It is hard to tell you precisely how much water you need to add, as this largely depends on the size of the bin and on the temperature. Too much moisture can adversely affect the balance of air and water inside the bin, so we certainly do not want to overdo it. As a general rule of thumb, the pile needs to be about as wet as a wrung-out sponge.

The most efficient decomposing bacteria thrive in temperatures between 40 and 70 degrees Celsius. Ergo, the hotter the pile, the faster it will turn into compost. Make sure the bin is in a sunny spot and – every now and then – use a pitchfork or shovel to turn the decomposing pile. The inside of the pile will be hotter than the outer edges and it is important to “mix the ingredients” to create an even balance. By doing so, you will also allow air into the centre of the pile. Another way of speeding up the cycle is to chop or cut any material that is added to the pile. The more surface area bacteria have to feed on, the faster they will break down the materials.

Do NOT add diseased plant material, weeds with seed heads, roots of invasive weeds such as dandelions, dead animals, pet feces, bread, meat (or fish), dairy products, cooked products or cooking oil. Also, do not add woody material such as tree or shrub branches to your pile, as they take a long time to decompose. Bark contains a substance called lignin which is difficult for bacteria to break down. Eventually, the rotting of lignin will be carried out by fungi rather than bacteria, but as fungi are much slower it will take a long time before their work is completed.

Play by these rules and you should be able to produce wonderful organic matter that will improve the quality of your garden’s soil. Finally, some gardeners like to add layers of soil to their pile, others like to sprinkle a handful of lime overtop every layer of waste that goes in. Personally, I do not think adding soil is necessary, but it will not negatively affect the process either. Adding lime can be useful, because the bacteria that do the work prefer conditions that are not too acidic. By “sweetening” the soil (i.e. neutralizing its acidity) you are improving working conditions for your labourers, which is never a bad thing.

Next week, we will take a look at “the other bulbs”, summer flowering bulbs and tubers.

Until then, happy gardening!

René Trim

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About René
René Trim was educated and trained in The Netherlands, before moving to Canada in 2000. After studying the differences in climate and season faced by Ontario gardeners he established Trim Garden Design and Rescue in May 2002. A gardener since the 1980’s, he has a wealth of knowledge and experience, a vast library of reference materials from which to draw answers to various garden situations as well as an enthusiastic and professional staff.