Do you want all perennials or are small flowering shrubs possible? How tall do you want the plants/tree to be compared to the house? Is a small ornamental tree in the mix - say 10-12' tall. How tall is the pine next to this area? If you cut the future garden in half with stepping stones, will there be a seating area - a small bench? Looks like a small slope; how's the drainage? Any chance this garden could go back far enough to include the chickadee bird house? Do you want that 'secret garden' feeling in 5 years or straight-away, easy access perennial garden?

I don't expect answers to so many questions,teapot, just offering some ideas.
Jane

Make a scale drawing of it. Draw a center circle for the birdbath, then add the possible paths, and see how much you have left. It isn't going to be a lot. Planting it with annuals and a couple of structural perennials like tall grasses whose main job is to look like something during the winter is a definite possibility.

Yes, we've done the scale drawing of it and we can plant 3.5' deep all around. I think we're going to go with thirds rather than quadrants or halves. We won't be sitting in the center at all - the center and path is more just a way to access all the parts of the garden easily. I found a plan on bhg.com that I could tweak to make it work in here - maybe square out the circle so that there are taller plants in teepees in the corners and the rest of the garden consists of mostly shorter plants/flowers so that we don't have to worry about the optimal view (from the center or from streetside) of the garden.

If your concern is access to the plants, maybe you could strategically place stepping stones throughout. Otherwise you end up with paths to nowhere.

You mention a birdbath. Is that supposed to be a focal point? Bird baths aren't very tall - do you want plants taller than the bird bath?

Why a circle? I only ask because I ended up with a circle garden by chance. If I had planned it better, I would never have made a circle. Circles seem to ask for formal plantings, which is not my gardening style.

What are the rest of your gardens like?

@ Pixie_lou - no, we want the birdbath to be the focal point. The paths will lead out towards the back and another to the yard to the right of the circle. The Husband came up with the circle and I thought it looked good. Maybe at some point, we will extend it into a labyrinth garden - that would be neat or put a couple of chairs in the center and build up the garden beyond the current limits for a secret garden effect.

@Jane - in a few years we can extend it, but right now we just want something a little bigger than what we had and a little more involved (after our spring flowers bloomed, we really didn't have anything else going on).

Since you are making the birdbath, I'd try to make it a bit taller than the typical birdbath. (My birdbath came from Lowes and is about 24" tall). SInce you want the bird bath to be the focal, you want to limit the plants to about 1/3-1/2 the height of the birdbath.

I would form a 5' diameter circle in the center. I would put the birdbath there, and then surround it with a low ground cover shrub - maybe a mounding juniper. Something that is evergreen and will look decent in winter. I would intersperse daffodils and tulips or other spring bulbs through out the juniper. Put the earliest blooming closest to the center and the later blooming ones on the outer edges of this inner circle.

Since you want a walkway, I would then make a 3' wide pathway around this center circle. Anything smaller isn't really walkable and tends to look more like a mistake. That leaves a 2-1/2' ring on the outer edge of your circle. Here I would try to find mounding perennials no taller than 12". Maybe some of the shorter varieties of shasta daisy or coreopsis or some stella doro day lillies. Stick to 3 or 4 different plants total. For a foliage interest plant, you could try a silver mound artemesia or a hosta or a sedum. Pay attention to your colors to make sure they all work well together. You could add some annuals the first few years while you wait for the perennials to fill out - but again, make sure they are short.

I would plan all 4 quadrants identical. I haven't done the math to figure out how much space 4 walkways would take up, so not sure how many plants I would recommend per quadrant. But as Mad said, the pathways will eat up a lot of space.

Lastly I'm thinking some alliums could look cool if interspersed in this outer ring. Their foliage dies back and you get the vision of floating bubbles. Even though they are taller, I think the circle shape would work with your circle plan, and as well the lack of foliage shouldn't distract from your bird bath.

Is the birdbath going to be visible from a porch or other viewing area? I ask because we have one that gets afternoon shade that we can watch from an east facing porch. It is so much fun to watch the birds. I would suggest you place the bird bath someplace in the yard where you can enjoy it.

I think a birdhouse on a pole would be fun in the center or maybe a structure for a climbing plant.

I have found that the plants on the north side of my circle garden need to be shade lovers. Blossoms on day lilies twist to face the sun which means they face away from us when we sit in the yard. Not all flowers are that sensitive to the sun.

The tall garden phlox I planted in my circle garden is much too tall and needs to be moved. I think columbine and fringed bleeding heart would do well in your location. Some smaller hosta varieties would be nice. But not good for winter interest. Not sure if you have enough sun for a spreading cotoneaster. Birds like the berries.

I put in a circle garden (10 feet, I think) years ago I'd planned to put a grass or something similar in the middle, and a garden designer told me to place it to one side, and I put a hydrangea to the side too. I did, and it looks dumb. The hydrangea never bloomed and I pulled it. I've changed that center plant many times...this year I put in a tree peony. We'll see what happens next year.
My garden style is kind of "cottage" so things are really mixed up. This garden has phlox and at least 15 kinds of daylilies, heuchera, geraniums (perennial, not annual), veronica and more. Have fun planning!

I'd love to see photos of these various circle gardens. There used to be a very large circle garden ( 30-40' diameter) in my town that was visible from the road. It was quite informal, with veggies, perennials and shrubs and a couple of tiers of paths. I found it appealing and really enjoyed seeing the changes in it over a season and over the years, but it isn't maintained any longer. I think that perhaps the land was sold.

My circle garden is only about 12' in diameter and right now looks a mess. It will look better when something starts blooming like the echinacae and white phlox but I think everything I have in it is too tall and spreads too quickly (i.e. threadleaf coreopsis).

The shape of the garden bothered me so a couple of years ago I asked for design help on garden web. It looks better now that I've added a kidney shaped garden on one side. Unfortunately, I think we put it too far off to the side except when a trench was dug last fall for a water line to the high tunnel, it got close to the new bed. If the bed had been closer to the circle garden, the trench would have gone right thru it.

Behind the circle garden are the rectangular veggie beds so the circle was like a sore thumb when it was by itself.

Thank you all for the ideas. I would love to see pix of these gardens too! I've added a few daylilies, planted some cosmos (too late in the season so not expecting much), going to add a couple of hydrangea and more irises for next year - I got from a friend cleaning out her garden. I'm going to put some hosta in the shadier part of the garden. I guess I'm going to go with the more cottage-y look too instead of with the symmetrical formal circle garden look.