That's right, it's one of my pet peeves because I see way to many people, (including contractors), just wasting their money when applying mulch to their landscape beds. That's not to say that mulch shouldn't be used around shrubbery, I believe that quality mulch is one of the best ground covers for plants. It provides cooling from the suns heat, retains moister for the plants, ads an attractive color, and gives some weed protection. Where I see the waste of money is in the weed barrier fabric that everyone seems to want to put under the mulch. This is not necessary because of the for mentioned factors. Because mulch can hold moister and with the small grains of dust and dirt that can naturally blow into the mulch; weed seeds that can also blow in with the wind will root themselves right into the mulch. The mulch will provide enough cover as to kill the weeds under it so, you do not need the weed fabric. Fabric can also stop a good amount of water from getting to the roots of your plants. Many of the available fabrics have a run-off factor, more so on hills. It also makes it very difficult to add new plants to your beds later, and can stop perennials from growing larger or expanding. Here is what I do for new beds:
Preparation of a new planting bed.
1) Outline your bed area with some form of marking system. I use field marking paint.
2) Spray inner area with Vegetation contact killer. Be careful not to go outside of your lines or over spray were you don't want to kill vegetation. Be very careful around plants in that area. Remember, Vegetation killer is just that, it will kill what it lands on. Allow area to begin dieing off; when lawn and/or weeds look to be yellow or faded, you can begin to work the bed.
3) Trench or install your edging around the border of your bed. I recommend some form of edging that goes into the ground a minimum of 4 inches to prevent the grass from growing into your bed and eliminate your trenching/trimming each year.
4) Bring in any soil you need to add to the bed. I.E. if you want to raise the bed above the ground level. Rake out to a pre-planting grade.
5) Plant your area with desired plants. Be aware that you will be adding a 3 inch or more cover of mulch to the bed later so, you may want to leave the plant/pot ball up an inch or two from your final grade of soil to allow for this mulch cover. Note: if planting a perennial bed, you should use a lighter cover of mulch as not to prohibit growth or expansion of the perennials. You may also want to plant perennials after you apply your mulch cover.
6) Adjust and rake out the final soil grade of your bed and apply your mulch cover. Note: Do not bury your plants with mulch. Many people pull the mulch right up tight to their plants and end up killing the plant. Too much mulch next to your smaller plants can suffocate them; they need air flow under them so they don't suffocate or rot off with too much water.To prevent weeds from over running your beds, apply a weed preventer to the soil in the spring after you fluff and/or add new mulch. This will prevent up to 75% of new weeds from germinating. If you see weeds starting to grow, spray them when you see leaves forming with contact killer. This will stop all that kneeling and pulling of weeds that I know you just love to do. Two factors will stop your preventer from working well; 1-if you disturb the soil like pulling weeds or digging in the area. This breaks the weed barrier that the preventer makes. 2- if you get a week of 90 plus degree temperature it could knock out the preventer's percentage of effectiveness. You may want to apply it twice a year,(spring and end of summer), if you have a large problem with weeds in your area.