Answer: Your perennials will need soil that is loosened in order to grow their root systems and establish. If the soil is very dry it will be hard to dig into it. You could wait until a day after a rain, or water the ground the day before you dig. That should soften it somewhat.
Remove large stones and rocks and work in several inches of organic matter such as compost, then level the area and plant. Perennials can send their roots as deep as ten inches or more. If you hit a layer of solid rock underneath where you want to plant, you can make an informal raised area to plant into instead of a boxed style garden.
To do that, loosen the soil, add organic matter and build it up, but leave a bare edge. Cover it with mulch to prevent it eroding. You can go about six inches high this way.
Since you have soil problems, always use an organic mulch in your garden. Keep it between two and three inches thick, replenish it as needed. This will help add organic matter and loosen and feed the soil over time as it breaks down.
Good luck with your flowers!
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