Ann's Organic Garden: Smother and burn: No mercy for weeds

Indeed, mowing every week or two will quickly turn a rough meadow into a semblance of a lawn, killing most coarse-leaved weeds. However, tap-rooted weeds such as thistles won't be killed, since the basal rosette lies so flat to the ground.

Another excellent weed-suppressing technique is smother mulching. This involves layering with a coarse, non-nutritive mulch to a depth that weeds can't penetrate. Even stubborn weeds can be smother mulched with coarse bark chips. After you remove all the root balls you can manage from an infested bed, spread coarse bark as a very thick mulch (8 to 12 inches or more).

This will inhibit annual weeds from resprouting and smother most perennial weeds. For instance, tests done in Kitsap County showed that about 80 percent of a mature ivy stand will be killed within three months by an 8- to 12-inch smother mulch of coarse bark chips.

Sheet mulching is also a splendid method for clearing garden beds-to-be. Simply heap a mixture of green grass clippings and shredded dry leaves or straw on top of the area you want to garden. A layer 2 feet thick is not too much.

Over time (as much as two years), this material gradually rots into compost, ready to be planted. In the meantime, almost anything already growing there will be smothered by such a heavy blanket and no new weeds will grow through it.

Tall weeds like nettles and blackberries may need firmer treatment. Here, the solution is to first cut back their prickly top growth (wear serious gloves when you do this) and dig out as much root as possible.

Next, mulch with coarse bark as deeply as possible. Keep your eye on the area and re-cut stems as they appear. Within a year, most areas will be ready to plant. Just rake away the bark and replace it with compost.

Most effective of all is a combination of smothering, cutting and digging. Start by mowing or weed whacking, then layer on a deep, (8- to 12-inch) mulch.

After a few months, the soil will loosen, making it easier to dig out any persistent roots. Discard them in the burn pile or trash -- never the compost -- and renew that mulch, keeping it at least a foot deep.

Any stragglers that make it through that will be easy to pull out, but don't just yank; use a shovel or sharp mattock and remove all visible roots. In time, you will win the battle.

Where large patches of ground are infested, weed flamers are highly satisfying to use and can be amazingly effective on persistent weeds. However, it's hard to use this tool selectively in planted garden beds.

In addition, flame weeders can be dangerous during droughts, when wildfires easily escape control. Flame weeders are fabulous for keeping gravel and paved areas weed free, but please do not use them on bark paths unless you have excellent insurance.

Resources

The Gardener's Weed Book by Barbara Pleasant (Storey, 208 pages, $14.95) describes more than 70 benign but effective weed-control techniques.

Northwest Weeds by Ronald Taylor (Mountain Press, 183 pages, $11.95) offers colorful photographs of the good, the bad and the ugly among that august company. The idea here is that not all weeds are bad plants; many are important food plants for butterflies, bees and other beneficial insects. By learning which weeds are serious pests and which can safely be left in place, you can spare yourself a lot of unnecessary work.

Ann Lovejoy, a Bainbridge gardener, is the author of several gardening books. She can be reached via mail at: 8959 Battlepoint Drive N.E., Bainbridge Island, WA 98110.

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