Answer: If you use an herbicide, always carefully read all of the label directions and then follow them. Glyphosate is a nonselective herbicide so be sure not to contact any desirable plants with it. Wait the full designated time after spraying before removing the weeds; the chemical needs time to move down from the foliage through the plant to the root where it actually kills.
Once you have removed the weeds, you might want to layer newspaper over the area and top that with your mulch. (Lay the paper about ten pages thick in an overlapping layer to eliminate gaps, dampen it to make it less likely to blow away as you work.) The paper will exclude light and so help prevent weed seeds in the soil from germinating. (Eventually the paper will rot away.) Keep your mulch several inches thick year round.
Using an organic mulch around your shrubs will help feed the soil over time gradually as it breaks down. It also helps keep weeds down and helps keep the soil more evenly moist during dry spells.
You could plant yews and nandinas together, yes. They need a well drained location in sun to part shade. Space them to allow for their mature size. If you like the look of the ornamental grasses you could add a grass as well, they should do well in the same type of location. If you use a grass, make sure you will still be able to see clearly when pulling out of the driveways -- some grasses are very tall, especially when in bloom. Again, allow ample room for the grass to grow wider over time.
If you are planting a bed, it is usually easier to prepare the overall area rather than do individual planting holes. First remove weeds and then prepare the bed by loosening the soil down about ten inches and adding organic matter such as compost, old rotted leaves, well aged stable manure/bedding, and/or milled spagnum peat moss. Set your shrubs at the same depth as they grew in the container. Loosen or cut any encircling roots so they can grow out into the surrounding soil. Firm the soil around the roots and water thorouhly to settle any air pockets. Mulch with several inches of organic mulch in a flat layer over the root area.
Then water as needed to keep the soil evenly moist like a wrung out sponge.To know if you need to water, dig into the soil with your finger. If it is damp, do not water yet. When you do water, apply it slowly and thoroughly so it soaks down to the deepest roots. After watering, wait a few hours and then dig down to see how far it soaked in; sometimes it can be surprising. It is better to water deeply less often than to sprinkle lightly every day. With new shrubs you will need to check the moisture level and water if needed for the first year any time the soil is not frozen. After that, you may need to water in dry spells.
Enjoy your new plants!
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