Composted manure and compost are not the same thing and are not interchangeable. Manure, if it has been aged a minimum of 90 days for above ground crops and 120 days for root crops can be applied to soils, or fresh manure can be applied to soils as long as the date of harvest is within those time frames.
What you are doing is creating a pot where you are planting by just amending the soil where the plant is going and that can allow watere to flow more easily into that mix but not out. You need to work at amending the whole planting area so drainage will not become an issue.

Yes, amending individual planting holes has been found to be counterproductive in the establishment of new plantings. In addition to creating soil interface issues than can impact drainage (as mentioned above), plant roots tend to circle and concentrate themselves in highly amended soils rather than moving out laterally through the soil horizon. The recommendation is to backfill ONLY with what you removed from the planting hole or the indigenous soil. If you DO need to amend, do so over the largest area you can manage rather than individual planting holes or apply any amendments as a top dressing.

thanks guys, it all make sense now. I have been doing the individual hole amendment and saw no return on my addition effort.

Amending a large area for shrub/roses planting is a lot of digging, going 12-18" in heavy California clay is too much for my little electric rototiller which can only go about 6" deep.

I wonder how much heavy mulching (like 8-12") can help?

Tilling organic matter into soil kind of gets it there sooner, but not better since the Soil Food Web still needs to work on the OM to get it really incoporated into the soil. Putting the organic matter on the soil as a mulch will also get that worked into the soil, in time. Often I see someone complaing because the mulch they put on their garden "disappeared" although they did notice that the soil improved some. Your soil did not get in the shape it is in overnight and you are not going to make it better overnight.

Depending on how large an area you are working with, you might consider snaking a 'nutrient trench' through your flower/shrub beds.[fertilizer, kitchen scraps,leaves, etc.] With the addition of worms, it would be a combination of trench composting and vermicomposting.

The soil critters will turn your clay into primo loamy soil wi/o a lot of backbreaking work. If you are near here, I can give you some of my wriggling-workers.

Here is a link that might be useful: Vermicomposting trench video

Hi BorderBarb, great idea. Too bad I am in the SF Bay Area, too far to get your wrigglers :(

Few questions:

1. There are vendors on local Craigslist selling red worms. Can they be released to trench/bed? I don't think that they are local species, right?

2. I have roughly about 130ft of flower bed, ranging from 5' to 15' wide. So I should just dig a trench in the middle of bed of say 18" deep?

3. I wouldn't have another green stuff to fill that trench. How about me buying a few bales of Alfalfa hay, straw and bags of manure?

4. Being a narrow and shallow lasagna bed/trench, how often do I need to refill them? would it help if I actually use low pressure drip/sprinkler over the trench?

5. Do I need like 2 of them in parallel for the wider part of my bed which is 15ft wide and about 60ft long?

Thanks again for helping.

8 to 12 inches of mulch over the top of plant roots is not a good thing. You need to remember that those delicate feeder roots require plenty of oxygen in order to continue to grow (cell division AND elongation). If you put too much mulch down, the roots struggle for oxygen as well as water. It's also more difficult for the gases that build up in the soil (CO2, etc.) to escape into the atmosphere.

So, consider a 2 to 4 inch layer of mulch and/or compost, and keep it refreshed as it disappears into the soil.

By the way, we have very hard red clay here in Northern Alabama where we live. We rototilled our planting beds (perennial gardens, veggies, woody stuff) once, adding lots of composted wood chips, and other organic matter. That was about 5 years ago. Since then, we've just continued to maintain a layer of mulch on top of everything. It's STILL hard, red clay but everything we plant in it thrives.

Just40fun ---- [1] To answer Q1, I must relate how I got my ÂherdÂ. I did not buy them, so canÂt for sure identify the species - Eisenia foetida or Eisenia Andrei - But from what I pick up from the Vermicomposting forum, quite often when one buys one variety, you get the other or a mixture.
But they are definitely composting worms. I harvested them from the earth below a pile of aged horse manure, and from my compost pile. I then put them in a Âpit with horse manure, compost, kitchen scraps, and paper shreds for food. And you canÂt believe how they have multiplied!

You can harvest from a manure pile, buy online/locally, or even purchase bait worms ["red wrigglers"]
// [2] Since my garden consists of smallish terraces, I have no room for trenches, so hesitate to prescribe for your situation. That video seemed to give a pretty good idea  and then you can alter for your situation. My sister Âsnaked a ditch through her perennial bed, filled mostly with horse manure and worms and covered with cardboard and topped with the mulch for the entire bed. She is 40 miles inland [hot,dry] and has clayish soil. She reports to me that she finds worms whenever she lifts the cardboard and the soil in her garden is improving. I believe the worms use the trench as a home base, and move into the soil, when conditions are moist enough.
[3] Fill your trench with whatever is handy  manure, paper shreds, leaves. Hay will heat up as it composts and might make the worms unhappy, so donÂt fill entire trench with hay. After it has composted a bit, the worms will migrate into that material. But by all means cover the trench with a layer or slab of hay/straw to control moisture and temps.
[4] CanÂt say how often you need to refill. Too many variables.
[5] I would suggest starting small Â. One trench this season, and then if successful, add more each season.
BTW - After 30 years of amending, my clay/DG-combo soil has morphed into lovely loose loam. In addition to double-digging, sheet composting, mini-worm ÂcondosÂ, IÂm a great believer in planting cover crops with deep, strong root systems, to bust the clay. And voila, an OVERNIGHT SUCCESS!

Reference:
http://en.wikipedia.org/wiki/Eisenia_foetida
http://en.wikipedia.org/wiki/Eisenia_andrei

Here is a link that might be useful: Plant Roots

Vermicomposting Trench sounded like fantastic idea. Anyone here has hands on experience to share?