Depending on what you are using to kill the grass it could be a long time. The information on the package should tell you everything you need to know about wait times and how it affects other plant material.

A couple years ago I had a very weedy area and hired a guy to clean it out for me so I could plant bluegrass there. He killed everything with Roundup and said I only had to wait two weeks. So I waited three weeks, planted the grass and it did fine. He said that the roundup breaks down in the soil in about 14 days.

Having said that, I'm sure there are alot of people who would disagree and say that it can last much longer. I've also had some experiences with weed and grass killers that seem to last for about a year or two. So you need to be very cautious with poisons.

Corn gluten meal is an organic pre-emergent that will prevent weed seeds from germinating in the soil for about a year. It won't prevent the grasses that spread by rhyzomes though so you would want to just use it to prevent weeds popping up from seeds that are spread by birds or the wind. Corn gluten is available at feed stores and at some garden stores.

One thing about your heavy clay, it is normally very high in nutirents and although it's hard to garden in, it is good for the plants. Besides adding the compost, try also adding zeolite. It's a natural, organic material that will enrich the soils and make it less hospitable to weeds. Weeds seem to prefer to grow in areas where nothing else can. They prefer poor soil. So by enriching your beds weeds are less likely to take hold.

When you do get some nice new things planted be sure to mulch well. This will deter weeds, but it also makes any weeds that do manage to pop up much easier to pull. Compost loosens the soil, mulch helps keep it moist.

One other thing I would suggest is to introduce earthworms into that bed. Earthworms have their own kind of magic they do on your soil, by tilling it with their burrows and fertilizing with their castings. They will also eat dead plant material and dry leaves that fall into the bed. Composted cow manure is a good amendment to add when you have earthworms too. Cow is good because the rumination process kills most weed seeds. Domesticated rabbit manure is good because they only eat processed rabbit feed and it has no seeds.

I use a 4" cedar mulch in my rose garden and the weeds and grass actually grow between the soil and the mulch layer. Their roots are in the mulch so when I pull them out they come right up. I can shake off the mulch and toss the weed.

I know you're frustrated with your azalea bed, but you have such an opportunity right in front of your nose. You don't have to throw out those azaleas you know. If you pot them up, soak them for a few days in water with fish emulsion and hang onto them until you are ready to replant you could certainly put them back into the amended bed where I'm sure they would flourish. Keep in mind that most the other things you're talking about putting in there won't look like much in the winter. The good thing about the azaleas is that they fill out and stay green year round.

Cheryl

My pictures are gone, but read what I posted about bags and bags of leaves.

PS, I am using a friend's laptop. Hopefully mine will be back tomorrow.

Here is a link that might be useful: help for clay soil

From Monsanto's website:

"Spray Roundup WeatherMAX for annual weed control and plant the same day. If quackgrass or other perennial weeds are present, wait 3 days (72 hours) before tillage."

Because I like to make sure, I usually wait until the plant appears to be dying.........about a week.

Libby

Rather than spray weed killer, here is what I would do. Cover the entire area with multilple sheets of newspaper. Then a thick layer of compost followed by a layer of mulch. Leave this for a month or so, then plant. The newspaper blocks all light and creates a barrier. Everything under the newspaper will die and decompose helping to amend the soil. This method has worked very well for me. Wherever possible I avoid using chemicles in the yard.

Thanks everyone!
Cheryl- I do have another azalea bed on the other side of my front door so I'm not losing them entirely. I did transplant three good ones to another spot with more shade as the front of my house gets pretty much full sun. Hopefully those will be ok. I will have to try the corn gluten. I actually was looking at some a week ago but wasn't sure if it was any good. Beleive me I have tried everything but weed and grass killer in that bed. Last spring I dug out and ripped every bit of grass and weeds I could,then added some compost to each azalea, then spread thick amounts of newspaper over every square inch and then mulched heavily. Summer came and back to square one! The grass had deep roots and runners along the foundation and then the builders put mondo grass in there as well and it came with some weird plant growing in it that spreads all over with tubers. The azaleas that I dug out yesterday are so root bound with tough fiberous roots that after 3 years look like they were just stuck in the ground. Now I know why they never grew. So I am down to my last option I feel. I didn't want to do it this way but for insanity reasons I must! lol

Libby- does that roundup weather max kill grass too? That is my biggest problem in that bed.

Looks like some kind of the Roundup brand is best so I'll have to get me some and spray away.
Meghan

Also, the azaleas may not be doing well unless they are in very acidic soil. I have pH7.1 and a gifted azalea never thrived, so I wound up giving it away to someone who had acid soil. Have you tested your soil? It's simple and cheap to test.

Unfortunately anything with really deep roots won't be killed by layering newspapers and mulching deeply. That mondo grass does spread by tubers or rhyzomes, so does quack, nutgrass, bermuda and a whole host of other grasses. Even solarizing doesn't kill them. You may also have some of these thugs creeping under your sidewalk. I had bermuda grass growing out of a light switch one time and found a runner that started about 5' away and grew up under the siding. So check on the other side of the walkway and you may want to trim the grasses about 3-4" from the edge of it.

Gottagarden is right about the acidic soil for azaleas too. And one thing that occured to me later was that I hope you cut some of those binding roots and teased them apart so they can begin to spread out and grow naturally. You'd want to have them spread out like a tent and set the plant on a mound of soil in the planting hole with the roots going outward and downward. That way they can all absorb the nutrients they need and those poor plants can grow.

For the record, roundup is a non-selective herbicide and will kill anything that it touches. Use it on a windless day, and protect your other plants with newspapers or dropcloth to prevent droplets from coming into contact with them. My neighbor sprayed our fenceline with it on a windy day and killed my blackberry bushes 20 feet away. I painted roundup on the leaf of a pecan seedling that was coming up in the middle of my rosebush and they both died. So just be very careful with it. Cheryl

What the grass did was grow along side the newspaper and pop out of the edge. Very frustrating! I know about the azaleas needing acidic soil. I have acidic soil but not along my foundation. I transplanted the three I dug up and put them with my dogwood in partial shade they should love it there. My dogwood surley is happy. I did tease out the roots and cut away some of the tough fiberous roots before I planted them. Then after adding lots of compost I spread used coffee grounds all around. They should be good to go.

Now as for the roundup I will be very sure after that warning to make sure I am as careful as can be. The dropcloth or sheet is a very good idea. That does make me nervous though of my neighbor ever spraying along the back of my fence and killing all my beloved roses! Very scary! I just don't see any other way to finally rid myself of the grass and weeds. I have a very bad back and constantly trying to battle them by pulling and digging them out kills it. I'm tired of it and it looks terrible. That's why I tried the newspaper thing with the mulch to try and see if it would work before resorting to chemicals.
If anyone knows of anything else to try please let me know. Today is a pretty still day too. So I may go ahead and buy it and then go from there.
Thanks! - Meghan

You might consider an herbicide specific for centipede and similar grasses, and another herbicide specific for the weed with the tubers.

What comes to mind about a weed with 'tubers' is Florida betony, which shows up green about now, looks kind of like mint when it starts growing, has white roots and on the white roots are those tuber things that look like rattlesnake rattles. Is that the one? Atrazine is the chemical recommended by the manufacturer and local garden centers here to kill Florida betony. It kills some other weeds; I don't remember which.

Moving your azaleas to part shade was the smart thing to do. If the dogwood is happy, they should be, too.

Nell

Well I bought some roundup and luckily it had this foaming spray that made it really easy to apply without having to worry about the rest of my plants. Most everything is killed off but a few persistant weeds. The 3 azaleas I transplanted seem to being doing really well in their new home. I was already to till in a bunch of compost today but alas the now 3 days of pouring rain and more on the way for tomorrow has delayed the process. No rain in the forcast for all of next week so hopefully by the end of the week the saturated clay mush will be dry enough to work in. My darling 7 month old lab tried to help me by digging several giant holes in the muddy clay. *sigh* Now if I can only get him to do that in the dry dirt it would save me lots of back aches! lol

It's funny, I love this time of the year because it's perfect garden weather but I always feel so rushed to get everything done in time. Same thing in the spring. So for now I sit in limbo drawing out plans till I can get back to work! :O)
Meghan