Long term, mulch makes fantastic new soil and reduces weed infestation. Mulch is always useful to reduce evaporation, protect the soil and worms from erosion and increase your store of organic material.
However, sometimes you may results you hadn’t expected.
If you apply:
- the mulch too thinly – this can result in a light cover that encourages existing plants and seeds to thrive (they are simply ‘top dressing’ the weeds).
- mulch made of fresh grass clippings, weeds or prunings might contain seeds or tubers that resprout where you don’t want them.
- material that is highly acidic, or all one type of material such as citrus peel can attract bugs, but they are doing the job of breaking it down for you. Keep this type of mulch away from delicate plants until it breaks down.
- Rat food, yikes! Rats are not more populated in a healthy garden, only in unbalanced gardens with too much food waste. Control rat populations by keeping their favorite food in metal bins until it decomposes, then apply the composted food scraps to the garden.
- material that has not yet decomposed, you might start to witness nitrogen draw-down (when the leaves of plants near the mulch begin to turn yellow). It is wise to put a good layer of compost or aged urine or manure underneath the top layer of ‘green’ material.
- mounds of fresh clippings that generate heat and burn the plants below (this can be handy if you are wanting to burn out an area). Usually it is wise to keep the mulch in a heap until it has stopped burning (the burning kills weed seed within the heap too, so it is handy) then apply the mulch when it has cooled.
- heavy mulch full of naturally occurring allelopathic chemicals (such as eucalytpus) – this will not be kind to any tender, unaccustomed plants. Basically, be aware that non-natives may not like native mulches.
- mulch too close to the trunks of your trees can kill them. They can develop collar rot where the trunk suffocates, gets too wet and rots away.
- mulch that inhibits germination of good seeds from last season. If you find that you tend to get lots of seedlings in the paths of your gardens and not in the beds that is probably because the mulch you applied has stopped seedlings being able to sprout in the beds. Choose to mulch at the right time, after seed germination if you wish to find new plants each season.
Some materials do not decompose quickly (eg. hair, old wool, re-used cotton from an old futon) so they are good long term protection. The ideal mulch is living mulch which replenishes itself year after year. Living mulch can be edible such as sweet potato (kumura).
Learn to Design your garden to reduce repetitive labour and increase your harvest and pleasure.