Different mulches have different levels of weed seeds in them. By choosing a mulch that's low in weed seeds (such as Straw) you minimize the risk of bringing weed seeds into your garden. See Mulching Materials for a list of mulches and the level of weed seeds they are likely to carry.

Different mulching materials tend to come with a different range of weed seeds. By sticking to just one or two types of mulch you will limit the variety of weed seeds that have to be removed. I mainly use straw as it is relatively clean of weed seeds. It is also fairly cheap.  My second most used mulch is pea straw.  While it is not as clean as straw the main seeds that germinate from it are peas, which benefit the soil because of the nitrogen fixing properties of peas.  The also can be easily removed.

It also helps if you can get your mulch from a single source, say a local farmer or a stock and station store that buys it's bales from only one or two farms.  This is because weed seeds can be regionally quite specific.  But admittedly getting your mulch from only one source  is not always possible.

Chickens are wonderful at removing weed seeds from mulch. If you have chickens then place your mulching material in an area where your chickens can access it at all times and let them simply pick away at it for a while. Not only will they remove most weed seeds they will also add their manure to the mulch and break it down into smaller pieces.

I have a pen of about eight square metres at the side of the hen house for processing mulching material. The pen is totally enclosed to make it fox proof and has a small hatchway into the hen house so the chickens can access it any time. Any mulching material is placed in this pen for four to six weeks before being spread on the garden.


Sawdust has a particularly tough cellular structure that can actually draw nutrients out of the soil as bacteria tries to break it down.  If sawdust is to be used as a mulching material then it is best that it is broken down into a more composted state before using it as a mulching material. There are two main ways to do this :

Spread four or five centimetres of sawdust on your paths in the vegetable patch. At the end of a year the sawdust will have broken down enough to be used directly on your vegetable beds. Simply scrape it off your paths and onto your beds and replace with fresh sawdust. There are two down sides to using sawdust. The first is that you must get if from a sawmill that only cuts hardwood or pine timber. Treated pine or chipboard sawdust is full of chemicals that could contaminate your garden soil. The other problem is that Couch grass seems to love growing in sawdust. So if you have Couch in your garden it may penetrate your sawdust paths, and eventually get into your garden beds as you shovel the Couch contaminated sawdust onto them. While I have used sawdust on paths in the past it is not a method I use now, preferring to use grass or gravel paths.

If you keep chickens then you should consider using the deep litter method, and the best material for deep litter in the actual hen house is sawdust. Simply spread ten to fifteen centimetres of sawdust on the floor of you henhouse and leave it there for twelve months. The good absorbent qualities of sawdust means that during the course of the next twelve months the manure your chickens produce will be directly absorbed into the sawdust, which keeps the henhouse dry and relatively odour free. By the end of twelve months the sawdust should have broken down into a more compostable state and packed with nutrients from the manure. Simply shovel it directly onto the garden or into your compost bins as a great fertilizer boost. I have used this method of processing sawdust for a number of years now and highly recommend it.