TO MULCH OR NOT?
What is the big deal anyway? Why not just mulch, given the immense benefits of mulching? And what is mulch anyway?
Mulch is any layer of material applied or spread over the surface around or amidst plants or over a plain ground.
- There are several advantages of using mulch;
- Conserves moisture, which leads to deep and infrequent watering.
- Eliminates drying out of shallow root plants
- Adds nutrients to the soil
- Improves soil structure
- Encourages growth of soil microorganism
- Can be aesthetically pleasant especially for landscaped areas
What to consider in selecting mulching material
It should be readily available
Economical
Stays in place-not moved by wind
Adds organic matter to the soil.
It is free from weeds, pests and diseases.
The healthiest plants are those that get consistent supply of moisture and nutrients. Here is where mulch becomes invaluable. Exposed to water and heat, mulch start to break down releasing nutrients to plant roots earthworms and soil organisms. You need to weed before applying mulch as chances are that prevailing weed may breakthough the mulch layer.
How To Apply Mulch
The question of how thick your mulch layer should be has always generated debate among gardeners. The thickness of a mulch layer depends on the size of its particles. Large sized particle mulches like straw, hay and tree barks can be laid up to 10 cm high. These leave large air spaces that can have breakthrough weeds if you apply them too lightly.
For smaller sized particle mulch, a much thin layer is recommended. Compost, pebbles and pumice leave little room among them and therefore should be no higher than 6 cm. Otherwise you risk reducing the amount of oxygen supplied to plant roots.
In all cases, leave a space of 6 cm between your mulch a the stem of your tree or shrub. Having the mulch touch the tree stem can lead to stem rot due to water and moisture.
Types of Mulch
Compost
This is the best mulching material. Compost is organic matter that is well rotten. It is good because it enriches the soil with nutrients, improves the soil structure and drainage. It promotes growth of worms and other beneficial soil microorganism that improve the soil. In addition, compost minimizes evaporation and conditions the soil. You can easily make it own your own too.
Compost can be used in all situations; flowerbeds, vegetable gardens, pots and around trees and shrubs.
Grass clippings
Some gardeners prefer to use grass clippings from lawn mowing in flowerbeds as mulch. Others would rather leave the clippings on the lawn to shed it. Whatever ways you apply them, grass clippings make great mulch. They are high in nitrogen and make good feeding mulch. When combined with shredded leaf or untreated saw dust, they improve the soil structure due to the carbon content in leaves.
The only drawback of grass clippings is that if applied too thickly they decay into a slimy pulp. During periods of intense heat, this slimy pulp can get hot and burn plants. Avoid the temptation to use all the clippings at once. You can pile your clippings and successively add onto the mulch as it decomposes. Apply this mulch lightly at no more than 2 cm thick.
Use under fruit trees, vegetable gardens and flowerbeds.
Sawdust
Sawdust may be plenty and cheap but I have never been fond of it. You can use it fresh from the sawmill as it is highly acidic. Ideally sawdust should be piled out in the rain for a year so that rains and natural decomposition wash out the high acidity.
Apply sawdust only to a depth of 5 cm.
Sawdust mulch is preferred for acid loving plants like blueberries, rhododendron. This mulch is also good for soil that is too basic and needs to be acidified.
Bark and wood chips
A good mulch material as it breaks down slowly therefore avoiding the need for replenishing. The large pieces of bark allow for air and water to reach the ground. Wood chips are sourced from areas where tree felling has been done. For effective results, underlay your bark or wood chips mulch with compost first. Bark is more often viewd as decorative as it breaks doen slowly. These mulch is ideal mostly for trees and shrubs as it helps conserve moisture and adds interest due to the different bark colours that may be present.
Bark and wood chips can reduce the amount of nitrogen available to plants. This happens when bacteria has you notice to take nitrogen from the soil and use it to break down the bark and wood chips. If you notice yellowing of your plants, your bark mulch could be the culprit.
If the size of the bark or wood chips is small apply up to 2 inches. For large sizes a thickness of up to 10 cm is recommended.
Pebbles/pumice/gravel/Rock
These are ideal for cold areas. They absorb the heat during the day and release it at night. They are stable as they cannot be blown away. Since they are inert, they don’t take nitrogen from the soil to decompose.. You can choose coarse or fined textured material and some can be coloured to blend with the home.
The main disadvantage with these materials is that with time, they tend to get ‘’lost’’ in the soil and need more topping up. Rock pieces from limetone areas may raise the PH of the soil and therefore affect the performance of rhododendrons, blueberries and other acid loving plants. The fact that this material does not contribute to soil enrichment is a major disadvantage.
All of this materials which are mostly small in nature, should be applied to the thickness of 5 cm only.
The mulch materials are best used in driveways, rock gardens, around trees walkways and in steps.
Hay
Hay is good because it has high nitrogen levels and trace elements. When it decomposes it adds nutrients to the soil. Hay also improves soil structure as it is broken down and worked on by soil bacteria. It is relatively weed free unlike grass clippings.
Hay is primarily sold as fodder for animals and therefore applying it as mulch can be an expensive affair. It can also be carried away by wind.
Apply hay mulch to a depth of 10cm. It will eventually settle to half the thickness and may need to be topped up as it decomposes
Use hay mulch for hungry plants like roses and in vegetable gardens
Newspapers
Newspapers are rarely used on their own as mulch. Rather, layers of wet newspapers, with holes punched in, are laid on the ground and grass clippings, compost or leaves laid on top. Holes allow for water to seep into the ground.
Newspapers conserve moisture, are easy to undertake and suppresses weeds. Unless you use it in conjunction with other mulching material, it is ineffective alone. If applied too thickly this mulch can hinder water and air from getting to the soil and decomposition will be slowed
Newspaper mulch can be used in vegetable gardens, around trees and in flowerbeds.
Rubber mulch
The key advantage of using rubber is that it prevents old tires and rubber from going to the dump sites. Rubber is hardly enough to be used on walkways, playgrounds and drive ways. Rubber can be decorative as it comes in a range of colours. Rubber does not add any benefit to the soil like other organic mulch.
Standard rubber mulch is never beyond 10 cm.
Applicable only on driveways, walkways and playgrounds.