There are dwarf snapdragons, very colorful. In some areas snapdragons are perennial. You might like begonias. The mini roses can do well as borders depending upon your climate. I suspect mini roses would not winter over where winters are really cold. They come in a variety of colors. Some penstemons are small.

I'm not particularly familiar with shade plants. Small ferns can make a nice green border.

Lorna

Sisyrinchium is a nice little grassy plant whose foliage looks like a miniature iris. It is a native. (Blue Eyed Grass) Part shade.

One of my favs for edging or filling in is Iberis (Candytuft). Nicer than alyssum, evergreen. Will grow in sun or part shade.

Cardamon ginger is a nice small ginger for shade. I think it might be hardy in your area, it hardly died back at all for me. Doesn't bloom outside the tropics, but the foliage smells good.

Nell

My absolute favorite perennial blooming right now is Platycodon Mariesii and it is very compact. I have it in the front of one my perennial borders and it looks fantastic.

Here is a link that might be useful: Mariesii Bloom

Thank you very much for your interesting suggestions. I was unfamiliar with many of the plants and am excited to check them out.

You can keep a lot of plants small, even shrubs and trees, if you want to spend the time cutting them back and dividing. And don't forget vines - they provide the vertical element of garden design. So do hollyhocks, a quintessential cottage plant. : )

Diana