You need to go to a garden center near you and take your pictures with you you will get tons of help.

I also have a slope on part of my yard. Rain runs right off it so that it behaves more like a dry area. And it's tough on the legs to stand on the slope and weed or plant.

A 3 season perennial garden takes years to put in place and is a lot of work every year as plants need trimming, transplanting etc.

A lot of unrelated colors can look less than attractive in a garden. A lot of white plants interspersed between them softens the potential color clashes. Try buying white flowers for your new purchases and for your annuals this year, to soften the look. Another bonus is that white flowers are often more fragrant than their colored counterparts, and white flowers show off beautifully in the evening light. We visited the gardens at Versailles in 2016, and there are enormous beds of tall annuals and perennials in mixed colors. Lots and lots of white was used to soften it.

It is backwards to choose plants first then try to find places for them. I would not put HT roses anywhere in this alpine garden bed.

Instead of a strictly perennial bed I suggest a mixed bed. The rocky area would be enhanced with some dwarf conifers.

You would do well to post the same question at the Perennials Forum. The folks there know a lot about bed planning.

You can post more photos in your replies here. More pictures would help.

You can add 10 photos per post, and then add additional photos in follow up comments. From my perspective more photos are great.

Consider repetition. Look at how the repetition of white-flowered plants along the top of your formal rock wall gives a rhythm to that part of the bed. Right now your listed plants have one of this and two of that, and some of them aren't plants that will be happy with your growing conditions such as your hybrid tea roses. Having some plants with a year round presence that repeat throughout the garden will give it coherence, even in a garden that tends to have a lot of variety. So choose one or two plants that you will use in several spots around the bed such as the evergreen heather and Dianthus listed below. Alternatively, if you can make yourself limit the variety, plant large masses of a few kinds of plants, sort of like the mass of annuals in the lower right corner of your photo above but with perhaps a half dozen types for the entire bed. Picture a mass of bloom covering a 5' diameter mass of Dianthus or creeping Phlox. Stunning!

Choose plants that suit the conditions. At one point in my life I lived in a house with a similar chunk of ledge with shallow, acid soil. I found that planting a combination of evergreen, blooming heaths (Erica) and heathers (Calluna) along with a variety of low-growing plants that are tolerant of low water and sun worked well. Some of them were thyme, perennial candytuft (Iberis), Sedum, Hens-and-chicks (Sempervirens), low growing pinks (Dianthus such as D. gratianopolitanus), and basket of gold (Aubrietta). There are some low bulbs that will do well here also, particularly some of the species tulips, crocus, and small daffodils for really early flowers. Even though the plants I used were tolerant of low water, I did need to water this area far more often than the rest of the garden because it had so little soil and it was fast-draining. Post in the Perennials Forum and the New England forum for ideas on other specific plants that work well in this type of setting. Create a bed elsewhere (perhaps along the top wall of your parking area) where you can create a bed of deep, fertile soil for plants like your roses, lilies, hydrangeas, etc. that won't do well in this bed.

Celebrate the rock. Folks often pay a lot of money to create natural looking rock gardens where rock doesn't occur naturally and you have it for free! In my garden I used some very short rock walls but not many to level soil in a few spots and a few large rocks or lines of single rocks placed in conjunction with plants to do the same. Rocks will look most natural when placed partly buried. Where there was bare ledge, I didn't try to cover it up or dress it up with pots like your 1/2 barrels, I just left it bare and over time it did start growing some moss and lichens, and some of the Sempervirens and thyme crept up over the edges. I liked featuring the ledge because it's such a classic part of the New England landscape. In the planted areas, I mulched the soil between plants until it filled in to keep the soil in place, discourage weeds and help keep soil moisture more even.

Keep winter interest in mind. Choose a few shrubby evergreens like the heather or evergreen perennials like the Dianthus and Iberis so that you have year round foliage to complement the rocks so your garden has winter interest. It's easy to get caught up in the flowers, but in New England we have many months of winter, and having an attractive garden view helps alleviate winter blues.

On a practical note, don't rip out the grass next to your ledge garden until you have a plan and a general plant list of rock garden plants, and also have found spots for those plants you've already bought but not planted so that you don't get overwhelmed by too much bare soil. This area has potential to be a stunning show piece, and it's obvious that you have already put in a lot of work. If funds are limited which is often the case with new homeowners, several of my favorite rock garden plants can be started relatively easily from seed such as the low Dianthus and Iberis or one large pot can be divided at planting time and then redivided a year later. Often heaths and heathers can be found at big box stores as seasonal color plants, and since you have such a perfect garden spot for them (unlike almost everywhere else in the US) take advantage of that and snap up a few.

You know, some people pay big, big bucks to have boulders placed in their gardens. I'd view your boulders as a focal point, not something to be covered. I'd encourage you to think of it as a feature.

Look at articles on Japanese landscapes. Make an ideabook with pics from garden with rocks and make your plan from there. You will not see a lot of roses in rock garden pics. I'd find someplace with better soil to plant them.

Most of us find that our soil, shade, water, or other conditions limit what we can successfully grown. Often, once you accept those limitations, you can find great plants that will work for you, but if you start off drooling over stuff in catalogues without thinking about *your* garden, you might end up being frustrated.

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