Mulching Your Garden

Mulch is simply a layer of material spread over the soil surface. It is one of the cheapest, most useful jobs in the garden, and it pays you back all season.

A good mulch keeps moisture in through a dry Kiwi summer, smothers weeds before they start, and slowly feeds the soil as it breaks down. Once you get into the habit it becomes hard to imagine gardening without it.

Why mulch matters here

New Zealand summers can swing from warm and humid in the north to hot and dry inland in the South Island. Bare soil bakes hard, cracks and loses water fast. A layer of mulch shades the surface and slows evaporation, so you water far less often.

Mulch also takes the sting out of coastal and inland wind, which strips moisture from exposed soil. And as organic mulch rots down it feeds the worms and microbes that build good soil structure.

• Holds moisture so you water less through summer
• Smothers weed seedlings and saves hours of weeding
• Keeps soil temperature steady and protects roots
• Feeds the soil as it breaks down

Choosing the right mulch

For the vegetable garden, pea straw is the Kiwi favourite. It is cheap, easy to spread and rots down into the soil. Untreated grass clippings, lucerne and compost all work too. Keep these soft mulches away from plant stems to avoid rot.

For paths, shrubs and trees, a coarser bark or wood chip lasts longer and looks tidy. Avoid mulching with anything that has gone to seed, and never use clippings from a lawn that has been sprayed with weedkiller.

• Vegetables: pea straw, lucerne, compost, untreated grass clippings
• Shrubs and trees: bark, wood chip, coarse compost
• Avoid: seeding weeds, sprayed clippings, thick wet layers against stems

How to lay mulch properly

Weed the bed first, then water the soil well. Mulch holds in whatever moisture is already there, so laying it over dry soil just keeps the dry in. Spread a layer five to eight centimetres deep across the bed.

Leave a small gap around the base of each plant so the stem can breathe and stays dry. Top the mulch up through the season as it thins down, and dig the old layer in at the end of the year.