We've used large sheets of cardboard covered with mulch in the Sacramento cemetery, and it has helped. The idea is to block light from the soil. Pine needles, unless piled really deeply, may allow light to penetrate a bit too much.

We've also solarized in some areas, putting clear plastic sheeting over level, bare soil for at least six weeks in the hottest summer months. You need clear sunny space to do this. I tried it in my decomposed granite walkways in my veggie garden, and it didn't work terribly well, I think because the paths were shaded by the raised beds and towering tomatoes. In the cemetery, in full sun, it was pretty effective.

We don't have as much problem with summer annual weeds here because it is so dry, and we only water with drip irrigation or bubblers at the base of the roses. We get our annual weeds during our rainy season, fall through spring. After years of weeding and mulching in the cemetery, we definitely have less this year. Getting the weeds out before they set seed definitely helps.

We don't use herbicides. I've heard about using gluten as an organic pre-emergent but haven't tried it.
Anita

Putting down cardboard works great, I also put down roofing shingles and that smothers the weed, they are stiff and can be shoved around under the rose, with a hoe, so you don't have to bend down.... since they are heavy they don't disintegrate or blow like cardboard... after a few weeks I reach in with the hoe and pull the shingle out and shove it over another weed... they are dark and not noticeable like cardboard.... I go to Home Depot and get bales that are damaged for a discount... and use them for a walkway also... works for me..... sally

I posted a couple of years ago about how getting the cool-weather weeds out of the garden in spring was my most onerous chore of the year. But last fall I applied a heavy mulch of leaves in November and, voila! no weeds now except a few around the edges. If you mulch only in spring, it wears thin over the year. Try putting down the main mulch in fall.

I find Preen is a huge help

Be careful with fall mulching if you have vole problems. The mulch apparently hides them from the Air Force, and they ate half of Mary, Queen of Scots, and Caesar's Brother from underneath the leaves. It's more work to pile the leaves somewhere in the fall, then spread them in the spring instead of just spreading them after they've been bagged, but it just causes problems.

My cats can be out, and the squirrels run up and down the trees, the birds are hunting things in the grass, and everything is very normal. A hawk appears in the sky, and those same squirrels and birds instantly vanish. The crows may stick around and give alarms, but everybody smaller just goes pouf.

Around here they often use some plastic material, a bit like potato sack, just from plastic and cover whole garden with it, also pour stones or cocos mulch over it for decorative purposes. It does not work for me, since I got mixed border garden, but I can imagine it can work for pure rose garden.

I use preen and mulch. After that what you need to do is take out weeds before they go to seed. Dandelions, po-anna and wild violets are my worse weeds and it's most likely because a few years ago, I got lazy and let them go. If I can't get them when they first come up, at least get them before they go to seed. I also do use roundup especially in the driveway cracks. It seems to work best there.

Dandelions are very annoying here too, also if they get big even round-up does not work very well on them. What worked to some extend for me at least for the patio, was to poor boiling water over them - cooked dandelions do not seem to come back. x)

I grow many annuals and short-lived perennials and rely on seedlings of these plants every year, so I don't use either chemical sprays or a heavy mulch. I have developed the habit of doing a tiny bit of weeding each day, starting in late winter. Over the years, weeds have been less troublesome, especially in the beds that have not been disturbed too much. I also plant rather intensely, bulbs under perennials, annuals popping up all around the roses, etc. The weeds don't have much of a chance.

Preen's active ingredient is trifluralin. In rose hybridizing it is used to double chromosomes.

http://www.rosehybridizers.org/forum/message.php?topid=2884#2884

It is not a chemical that I would put in my yard. Why, please see:

http://www.scorecard.org/chemical-profiles/summary.tcl?edf_substance_id=1582%2d09%2d8

Here is a link that might be useful: link for scorecard

Is a byproduct of whiskey making, and is used as a feedstock. Iowa State tried to promote it as a pre-emergent herbicide.
I got some from a local feed mill. (I didn't ask where they got it, but they were way up in the hills.)
Rodents love it.

Then Iowa State took their webpages down.

The problem is: it works fairly well when the temperatures are in the 60s to 70s range. But my spring weeds come out and thrive when the temperatures are way below that range of temperatures.

Oh, about the wild, short and beautiful violets. Larry and I argue about them. I finally said he should leave one of my rose beds alone and I'd let the violets take over that bed. They have and right now are a spectacular carpet of deep green with strong purple blooms. Oh, and there are very few weeds there. The roses there have survived, the soil is moister because the violets inhibit water evaporation from exposed soil, and the violet roots are so shallow as not to interfere with the roses deeper roots. I, of course, think that they are good.

Ann, what did you say was the byproduct of whiskey making?

I agree with you on violets (and most other things). We have violets in the cemetery too and I find that they are lovely and don't cause a problem with the roses. Some people think they are weeds, and we even had a mystery weeder get in and try to dig them up in one of the plots. To me, they are a perfectly acceptable companion plant.
Anita

For info about corn gluten meal (which I do use), see:

http://www.hort.iastate.edu/gluten/?

Here is a link that might be useful: link for above

Three recent (2009 and 2010) trifluralin scientific papers:

Is it an Endocrine disrupting chemical? See:

http://www.biomedsearch.com/nih/Endocrine-disrupting-effects-herbiicides-pentachlorophenol/19368227.html

Is it found in city air? See:

http://www.springerlink.com/content/a3u6474u73mu7103/

And, is it found in pregnant mothers (150 women that underwent an elective cesarean delivery at term in a hospital in central New Jersey)? See:

http://www.biomedsearch.com/nih/Pesticide-concentrations-in-maternal-umbilical/19900697.html

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I recommend the application of the precautionary principle.

Here is a link that might be useful: first link above

henry, I'm curious. Is there any chemical that you would put in your yard?

buford, I use corn gluten meal for annual weeds. (I dig out weeds that make it past the corn gluten meal.) I use milky spore and beneficial nematodes for Japanese Beetles.

Michael I think you are right, the weeding in the early spring is the worst. I was thinking that maybe the mulching in fall would be a good idea at least in the most troublesome areas of the yard. Tried cardboard and newspaper in the bad area, but there is a slight slope and the heavier rains just make it slide. Hadn't thought of roofing shingles! That should work great! Thanks!
dell

I would never use Preen in my yard, either. It states that it is toxic to fish, and I have a koi pond. In addition, I live uphill from a creek that feeds into a lake.

We also will not use Ally (broadleaf weed killer). We noticed when we were using it, we didn't hear many frogs by the creek. The years we haven't used it, we have many, many more frogs. Maybe just a coincidence, but we believe it.

There aren't many pesticides that I'm willing to use. Sometimes I resort to grass killer for the bermuda grass, and sometimes I dab Roundup on stumps of weed trees, but mostly I pull, smother, or dig out the weeds. I have a gut feeling that any chemicals that I apply puts the microbial action of the soil at risk. I was brought up on the concept of, "Give me spots on my apples, but leave me the birds and the bees."

I should give the gluten a chance, though. It actually breaks down into beneficial matter for the lawn or garden. Seems worth a try.
Anita

I have this horrible spurge weed that practically took over my gravel in the front and got into my beds last year. I kept procrastinating, and it finally went to seed. It was pretty easy to pull up (though time consuming). Then I used Halts on all my gravel and the grass on the slope to the retention area. It worked great and has kept the weeds away. A few are sprouting now. I don't get many weeds in the beds. Last year I put down newspaper, and I use composted horse manure with pine straw (last year) or small pine bark chips (this year) as mulch. I only get sprouts from the hay in the manure (which seem to have stopped) and some other weed that comes from the horse manure, but they're few and easy to pull out. I wonder why they say not to use Halts in the planting beds - and on stone but I did anyway since spurge is very hard to deal with & it was the only thing recommended.

Sherry

I make the rounds of my local coffee houses and get the burlap bags used to ship beans in. I use it under mulch and it lasts a couple of years before disintegrating. It's also really easy to lift up to apply non liquid fertilizer. Yolana

UGH, I hate spurge. Some years I have that all over. It's usually a later summer weed, so I don't have any yet. I think the mulch is the best method. Unfortunately I have parts of my yard where the mulch is thin and I've been very lax about replacing it.

My worst weedy part is the front of one of my rose beds. I put mondo grass there, but it doesn't seem to choke out the weeds. So I'm now trying moss phlox in spots and I did use preen in the bare spots. I don't like to use mulch there because it spills on to the walk way when it rains and I constantly have to sweep it back into the bed.

Hum...I did not realize Preen was bad. I guess I will try something else

Ann, what did you say was the byproduct of whiskey making?

Hangovers? ;^)

I mulch with certified compost. A few weeds, only in those places I didn't mulch. I love mulch!

We have an asphalt driveway that has fissures in it that the weeds regard as an ideal home. The best way we've found to kill these is to spray them with ordinary white vinegar. This is also very useful for little weeds that come up between paving stones. Non-toxic and works every time.

Ingrid

Ok, HOLD THE PHONE, folks.

Henry, you are referencing PreeM, not PreeN.

PreeN and Amaze are 100% corn gluten meal. I've gotten size large bags of corn gluten from Gardens Alive, but if your needs are smaller, you can get it at Lowe's as Amaze (in bags by Green Light) or HD as Preen (in a large plastic shaker).

I don't know about Henry, but I did mean PreeN. The reason I won't use it is because of its toxidity to fish since I have several 'fishy' areas. If you don't have fish around, that may not be a problem for you. :)

Here is a link that might be useful: Scroll down to Environmental Hazards on PreeN label

As per the above link Henry is right, PreeN's active ingredient is trifluralin. Gardens Alive corn gluten is not what is usually sold as Preen.
olga

PreeN's active ingredient is what Henry said, Trifularin.

There are two types of Preen. The regular one does have the chemical trifluralin in it and does state that it's toxic to fish. So if you live near water or have a fish pond, I wouldn't use it. There is a organic Preen labeled as vegetable garden weed preventer that is corn gluten.

http://www.preen.com/products/preen-vegetable-garden-weed-preventer

THANK YOU, BUFORD! You saved me from taking a picture of the label on the shaker bottle in my garage!

I must say, it's pretty dumb to label two different products with the same style labeling and with the same name.

y, it's pretty dumb to label two different products with the same style labeling and with the same name.

It's most probably completely intentional--if the store is out of one, customers in a hurry will go ahead and grab the other. Store-shelf marketing is getting sophisticated. Unfortunately.

erm, so what is Preen, what is corn gluten (I mean, i do know what gluten is - i think! but how does this affect weeding)?

Campanula, Wikipedia has a decent explanation:

http://en.wikipedia.org/wiki/Corn_gluten_meal

From the pictures of the labels, they look quite different. And the corn gluten one says ORGANIC. I know in HD they have a separate section for the organic stuff. But it is confusing. I remember seeing the organic preen, but didn't buy it as it said it was for vegetable gardens. I didn't pick up that it was corn gluten.

Buford - thank you! DH has been on me to use Preen since the gardening chemical store insisted it would make my life easier (too many weeds!) - but I refused because of the labeling. Now I know what to look for. :)

Amaze is a CHEMICAL pre-emergent- it is not corn gluten meal- I use it on my lawn for winter weeds. It contains 1% Balan and 1% Surflan.

Here is a link that might be useful: AMAZE® GRASS & WEED

Surflan is also used for chromosome doubling:

http://www.actahort.org/books/572/572_3.htm

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Some may feel that a chemical is safe if the government allows it to be sold. To those readers, the following recent post may be of interest:

http://www.washingtonpost.com/wp-dyn/content/article/2010/04/14/AR2010041404827.html

Here is a link that might be useful: Washington Post link