Mulch Madness

Wouldn’t you like to win the war on weeds without toxic herbicides, and with minimal hand-weeding? Natural gardening expert Carl Grimm from Metro showed us how to stop weeds before they sink their roots deep into your yard.

Mulch masters weeds and helps make gardens great
Mulch – which is a layer of material over the soil surface – is one key to keeping weeds at bay. Mulch also loosens soil and slows erosion that could otherwise pollute our local rivers and streams. Mulch even reduces watering needs and some can improve soil fertility. Mulch can help make your plants healthier and your yard more beautiful.

A few secrets ensure mulching success
Pull or cut existing weeds before you spread your mulch to reduce the chances of weeds growing through. And never pile mulch against plant stems or trunks as that could cause plant diseases. In general, the tougher the mulch: the better the weed suppression. And thickness matters – it should be at least three inches thick. While some mulch lasts many years, others decompose naturally, requiring topping off every year or two. 

Under-mulch barriers are a mixed bag
Landscape fabric or plastic sheeting is not recommended for planting beds since it gets in the way of cultivation. Heavy duty landscape fabrics can help block tough weeds under stone or gravel pathways, but weed seeds eventually blow into the mulch and grow there (albeit with a limited root system). A layer of cardboard or several layers of newsprint underneath mulch can also help suppress weeds for a few seasons after a new planting. Make sure to overlap the pieces of all under-mulch barriers at least four inches.

There’s a mulch for every season under the sun (or shade)
• Woodchips can be fairly durable and form a nice barrier with a casual aesthetic. They are good for shrub and flower beds and for paths. You can buy woodchips or get them from an arborist for free.
• Bark is generally long-lasting and can help make shrub and flower beds look more formal.
• Hazelnut shells are an Oregon specialty, with a unique aesthetic appeal. They tend to be a little more expensive, but last longer than most mulches. They’re good for shrub and flower beds, and for paths – but watch out when walking barefoot, ouch!
• Stone including pea gravel, quarter-ten gravel and decorative rock lasts forever and is good for plantings of alpine or Mediterranean plants such native Lewisii and lovely lavender. 
• Quarter-minus gravel over heavy-duty landscape fabric is a relatively simple way to make a good, solid path for walking, wheelbarrows and wheelchairs. Unlike pea gravel or quarter-ten gravel, quarter-minus compacts to form a nice, firm surface.
• Fall leaves are my favorite mulch for shrub beds, especially if they come from trees nearby. You’ll need to start with a nice thick layer (more than six inches) so it settles down to three inches over time.
• Compost is great for increasing soil fertility, but does not do a lot for blocking weeds. Use weed-seed-free compost from the nursery for best mulching results.
• Straw is nice for covering veggie beds in the winter if you’re not growing a year-round garden.

For more mulching tips and advice on non-toxic gardening, call Metro at 503-234-3000 or visit oregonmetro.gov/garden. For a great publication on Mulching Woody Ornamentals with Organic Materials by OSU Extension Service, clickhere.
 

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