This is by far the most important reason for using a mulch. Without a good layer of mulch (100mm or 4”), the sun and wind will cause the top 100mm of garden soil to dry out quickly putting your plants under extreme stress in a very short space of time. By adding mulch, the rate of evaporation is slowed dramatically and with water restrictions, any saving of water usage can only be beneficial not only to the environment but to your hip pocket.
Often we get complaints that plants are not growing well only to find when we visit that the garden has no mulch resulting in the garden soil drying out and even crusting, preventing water penetration.
Having a physical barrier on top of the garden soil will inhibit weeds. Once a seed germinates and reaches the garden soil surface it needs sunlight to photosynthesize (produce food for growth). If a mulch is in place, just its physical presence will prevent most, if not all, potential weed problems thus allowing your plants to thrive without competition.
NB. Don’t use plastic under mulch, it prevents the passage of water and gases into the top soil and therefore this can hinder plant growth. We suggest you use a biodegradable mulch mat or newspaper.
This is another benefit of having this physical barrier. In our Queensland climate, top soil will absorb a considerable amount of heat, which in an un-mulched garden causes damage to sensitive plant roots near the soil surface. Also in those areas that have mild frosts, the mulch will again moderate the temperature making your garden soil a more “enjoyable” environment for your plants to grow!
Replacing organic matter
As the mulch decays, it helps maintain the soil’s open free draining structure. This can be seen if you walk through any rainforest or bushland where the ground underfoot is covered in decaying organic matter or nature’s mulch.