Answer: Clay soil is not a bad soil, it just needs to have organic matter added to it such as compost, old rotted leaves, milled spagnum peat moss (not peat humus) or similar fibrous materials. Dig this in and loosen the soil to about ten to twelve inches deep. Remove large rocks and roots, small stones are no problem for shrubs. You would do the same type of preparation for most soils, including sandy soil, so even if it is not clay this will be fine. (Clay is not always red.)
You should mulch your shrubs with an organic mulch two to three inches deep year round. This will help feed the soil slowly over time, keep down weeds, maintain a more steady soil moisture and temperature, and also adds organic matter as it breaks down.
Fertilizer is usually added based on the results of soil tests indicating it is needed, however you could use a general purpose granular or slow release per the label directions for shrubs. Look for an analysis such as 10-10-10 or similar proportions. It is better to underfertilize than overfertilize, so if in doubt use the lighter rate indicated on the label.
That should be it. Enjoy your shrubs!
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