Mulch suppresses weeds and helps make gardens great
Mulch is a layer of material spread over the soil surface – it’s one key to keeping weeds at bay. Mulch also loosens soil and slows erosion that could otherwise pollute local rivers and streams. Mulch even reduces watering needs and some types can improve soil fertility, making your plants healthier and your yard more beautiful.
A few secrets ensure mulching success
In general, the tougher the mulch, the better the weed suppression. Whatever type you use, it should be at least three inches thick. 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 – that could spur plant diseases. 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 under a layer of mulch in planting beds gets in the way of cultivation.
- Heavy duty landscape fabrics can help block tough weeds under mulch in 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 some weeds for a few seasons after a new planting. This does not work as well for tough weeds like spreading grasses, creeping butter cup, dandelion or field bindweed.
- Overlap the edges 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, sometimes for free.
- Bark mulches are generally long-lasting and can help make shrub and flower beds look neater and 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 mulches 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 from nearby trees are an excellent, free mulch for shrub beds. Start with a thick layer (more than six inches). It will settle down to three inches over time.
- Compost increases soil fertility, but does not block weeds very well. 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, but may contain weeds seeds.
Leave the leaves
Let your leaves lie on bare soil when they fall. No need to rake. You save time and soil.
- protect bare earth from eroding in winter rains and wind
- add nutrients to the soil while slowly decomposing, feedign the roots of tall trees and tiny plants alike
- help soil retain moisture and reduce watering needs
- provide food and shelter for soil organisms that in turn feed beneficial black ground beetles and many birds in need of winter food.
Tip: Don't pile leaves against plant stems or tree trunks to prevent fungal diseases.