Ornamental Sweet Potato Vine. Permission for use through Creative Commons. Photo by Tiglio Art's
In a perrenial bed, you might try to have something flowering at all times and certainly at the height of summer, it is hard not to get a display. However, at other times, you may have a solid mass of green with only a bloom here or there to break it up.
There are various strategies for coping with this including incorporating plants with strong structural shapes.
You can also look for plants with interesting and contrasting foliage. So even when there is no flower, there is still colour. Leaves don't just come in green. They can be steel-blue, grey, lime, pink, purple, peach, white, yellow, red, tan, orange, almost black and mixtures of the above.
Thankfully many classic foliage plants are also shade lovers, a place not conducive to heavy flowering:
3. coral bells
Coleus. Shared through Creative Commons. Photo by jam343
Coleus = Colour
Don't just think of Coleus blumei, otherwise known as the painted or flame nettle, as a plant that you buy from the nursery every spring to pop into your planter box. It is extremely easy to root and overwinters happily indoors. If you know someone with a coleus you envy, ask for a cutting and stick it in a glass of water. You too will have that plant before you know it. As winter approaches, either dig up the plant or take cuttings for next year.
Oh and though traditionally it is known as a shade plant (colour fading in the sun), some are supposed to be tolerant of heat. I have never tried them so I don't know and there is no shortage of plants that look great in full sun.
Coleus is a 'tender perennial' BUT if it sets seeds, it soon expires.
How sweet is the Sweet Potato Vine
If the spot you need to jazz up is sunnier, you'll be happy to hear that the purple colour in plants is their version of a tan so it deepens in the sun. Many, many plants have darker versions, but the one I would like to focus on is the sweet potato vine, otherwise known as Impomoea batatas
It comes in a host of colours from chatruese to cerise to bruise purple. The local nursery has an agricultural sized table of varieties. And like the coleus, sweet potato vine can be 'easily' rooted from cutting and overwintered.
That's what I might try and do with this little surprise.
Sweet potato sprouts
I noticed some sprouts on my sweet potato so decided to let it grow, figuring that it would be some dull shade of the aforementioned standard 'cholorphyll' green when what before my wondering eyes did appear but variated purple and lime green. So perhaps it's just this colour because it's stressed and maybe it will revert to regular green later, but maybe not!
All about coleus by wikipedia
overwintering and propogating ornamental sweet potato vine by tuber
Annual or Perennial? That is the question
Grow a Coleus Standard - wild!