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Search Results for: Weeds | Search the catalog for: Weeds

Plant Answer Line Question

Keywords: Weeds, Lawns--Care and maintenance

I used to have a pristine green lawn and it has since been overtaken by crabgrass. I've tried organic and chemical weed-and-feed products to no avail. What can I do to get the weeds out?


Local plant expert Arthur Lee Jacobson has written about crabgrass (Digitaria sanguinalis) in his book, Wild Plants of Greater Seattle (2008): "Crabgrass is difficult to get rid of because it seeds itself at an almost unbelievable rate; mowing simply makes if flower nearer to the ground. Control demands diligent weekly hoeing and pulling by hand, from July through at least September. Even a few specimens left to reseed ensure more seedlings next summer."

According to Ecologically Sound Lawn Care for the Pacific Northwest by David McDonald (Seattle Public Utilities, 1999), weed invasions are best prevented by making a habit of aerating and topdressing to correct soil compaction and build fertile soil. He recommends that you "overseed at summer's end with locally adapted grasses to fill bare areas with grass rather than weeds. Correct acidity or poor drainage. Mow higher (2-2 1/2 inches, or 1 inch on bentgrass), fertilize moderately with slow-release or natural products, water deeply and infrequently in the summer. Tolerate some broadleaf plants like clover and daisies. Hand weed or spot-spray problem weeds in spring or fall to stop them before they spread."

There is additional information on crabgrass from University of California, Davis Integrated Pest Management.

Seattle Public Utilities has information on best practices for maintaining a healthy lawn.

Toxic-Free Future (formerly known as Washington Toxics Coalition) also has a helpful lawn care fact sheet that might be helpful to you.

Since the weed-and-feed approach to the problem was not effective (and chemical weed and feed should be avoided), I recommend trying some of the cultural controls discussed above (mow higher, only fertilize at appropriate times and don't use quick release fertilizer, water less often but more deeply, improve drainage by aerating, build soil by mulching). Solarization might be an option if the problem can't be addressed by hand-weeding combined with the other methods described.

Date 2017-08-08
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Plant Answer Line Question

Keywords: Weeds, Seeds, Compost

When is a seed a seed? My wife and I are in agreement on not putting weeds with set seeds in the compost (and the "Easy Compost" book says just that). However, we are less sure about weed flowers (probably OK), and what about seed cases that haven't formed seeds yet? I'm thinking in particular of foxgloves right now, as the flowers are coming to an end and leaving behind the undeveloped seed cases. I'm unsure whether to compost them or not. Just an aside: our compost pile doesn't get superheated.


That is a very good question. I found an article in Fine Gardening magazine which discusses harvesting wildflower seeds. It is relevant because it suggests that some unripe seeds may continue to ripen even after being harvested from the plant before maturity. Whether unripe seed will eventually germinate may have to do with the permeability of the seed coat: the more permeable, the more likely the chance it will germinate.

The book Seeds by Peter Loewer (Macmillan, 1995) says that plants with tough seed coats (like legumes and morning glories) "are virtually impermeable to water and must be nicked by the gardener or soaked in warm water for twenty-four hours before they germinate. If these jackets are not broken, scratched, or eroded, water never enters and germination never begins."

I have found several references to the immature seeds of invasive plants (Ailanthus, teasel, yellow flag iris, to name a few) being capable of germination. The Complete Compost Gardening Guide by Barbara Pleasant and Deborah Martin (Storey, 2008) "weeds that show up in your garden are fair game for compost, even if they are holding seeds. [...] Weeds that have not yet begun to bloom and lack viable root buds that help them grow into new weeds can be added to any compost project, but it is important to keep weed seeds to a minimum every chance you get. [...] In every climate there are plant criminals known as noxious weeds [...] Unless you are confident and committed to processing the compost made from noxious weeds with a high-heat procedure, collect them in a black plastic garbage bag and subject them to various forms of torture before dumping them in an inhospitable place. Cook bags of them in the sun, add water and let them soak into slime, and keep track of what works and what doesn't. If your superweeds survive your torture methods and you don't have a spot in your landscape suited to use as a little landfill, discard them as garbage."

If you want to be on the safe side, avoid putting anything seedy (even green and immature) in the compost, especially if the pile is not going to get especially hot and speed the decomposition process.

Date 2018-03-14
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Plant Answer Line Question

Keywords: Aphanes australis, Weeds, Lawns--Care and maintenance

Slowly but surely, what's left of my untended lawn is being overtaken by a small weed with fan-shaped leaves. It reminds me of a tiny Lady's Mantle. What is it, and is there any hope of getting rid of it without herbicide?


Your description sounds like Aphanes australis, whose common name is slender parsley-piert. The common name derives from the plant's leaves which resemble parsley, and the French 'perce-pierre,' meaning 'break (or pierce) stone.' It thrives in dry, exposed, or barren soils. North Carolina State University's Turf Center describes cultural control methods:
"Winter annual broadleaf weeds germinate in the fall or winter and grow during any warm weather, which may occur in the winter, but otherwise remain somewhat dormant during the winter. They resume growth and produce seed in the spring and die as temperatures increase in late spring and early summer. They quickly invade thin turf areas especially where there is good soil moisture. Shade may also encourage growth. Many have a prostrate growth habit and are not affected by mowing. A dense, vigorous turf is the best way to reduce the encroachment of winter annual weeds. First, select adapted turfgrass cultivars for your area and then properly fertilize, mow, and water to encourage dense growth."

It sounds like lawn renovation might be a good idea. If the parsley-piert has intense competition from a happily growing lawn, it will not thrive. Seattle Public Utilities has good resources on lawn care.

Date 2018-03-15
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Garden Tip

Keywords: Convolvulus arvensis, Hedera helix, Weeds, Invasive plants, Holly

In late spring watch out for seedlings of invasive plants bindweed (perennial morning glory), English holly and English ivy. Birds love to eat ivy berries, which are only produced by mature plants that have stopped climbing. The berries ripen in late winter, just in time for birds to "sow" the seeds in your garden. These three weeds are easy to pull up when their root systems are still undeveloped.

Date: 2007-05-17
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August 01 2017 12:36:01