I'VE FOLLOWED photographers around gardens for a decade now, and while I still can't take a decent photo, I have learned that plant shapes are what make a garden scene. Gardeners tend to deconstruct their spaces by fragrance, color and texture. These sensual qualities are so satisfying. But to group individual plants into a design that pleases, we need to carefully consider their shapes.

While sweeps of perennials and shrubs may appeal to the eye, a photo reveals a mass of undifferentiated foliage. I can't tell you how many times I've pointed out a pretty border to a photographer and they've advised me that in a photo it'll look like a boring mess. A photograph always reveals a garden's underlying structure, or lack of it.

Every grouping of plants needs a focal point to both attract and stop the eye. Arbors, pots, art and architecture all lend definition to the plants around them. But if our medium of choice is vegetation, we can get the same effect by punctuating with plants. It helps to think of plants in profile to get past noticing just the color, texture or bloom.

If you have rounded shrub after rounded shrub, or a jumble of perennials, your garden needs punctuation. One of the great joys of gardening is arranging and rearranging plants into effective combinations. Distinguish your vignettes by adding a few plants with defined and contrasting shapes. And if you string a few similar punctuation plants throughout several garden vignettes you've set up a rhythm sure to please both the eye and the camera.

Sometimes it's easier to understand a concept when you put it in an unfamiliar context. For instance, there's nothing particularly pretty about a saguaro cactus. A specimen all by itself looks stark and awkward. But stick a saguaro in the midst of flat desert, surrounded only by sagebrush and bumps of boulders, and its tall, architectural shape is as welcome as an oasis. The desert around the cactus looks so much better for it being there. Without the jolt of the cactus to stop your eye, you'd see nothing but endless low undulation. The same principle of contrasting shapes applies to just about any planting situation.

But here's the thing: Punctuation plants aren't just tall, skinny and pencil-shaped, although these are obvious choices. Accents depend on what is around them. In a garden of columnar trees, you could use a big, fluffy mound of ornamental grass to punctuate the rhythm of one tree after another, or maybe mix in a drift of rounded hydrangeas. An old chestnut my husband repeats all too often (and not about plants) is, "In the land of the blind, the one-eyed man is king." Any kind of plant with a distinct shape can be the one-eyed man that makes a planting work. And there's no need to be blind about our own gardens. All we need do is play around with shapes, and not forget our punctuation.

Making a point, from the ground up

Low: Black mondo grass is only a few inches high, but its ebony-colored blades are dramatic poking up through low-growing, pale groundcovers like lamium or creeping jenny.

Pacific coast iris have evergreen, sword-like foliage that slices through beds of perennials and small shrubs. Their beautiful May flowers are a bonus.

Mid-Level: Pillar barberry (Berberis thunbergii 'Helmond Pillar') is a narrow stick of tightly clustered burgundy foliage that tops out at 5 feet.

Ornamental grasses like Miscanthus sinensis and Stipa gigantea create a definite line and billowy effect with spiky foliage and tall, long-lasting flower spires.

Taller: Ilex crenata 'Sky Pencil' is a pointed column of Japanese holly with glossy evergreen foliage. It grows to 10 feet high.

Mediterranean cypress (Cupressus sempervirens 'Stricta') is a dense, columnar evergreen tree (to 60 feet high) that cuts a slice of dark shadow against the sky.

Valerie Easton is a Seattle freelance writer and contributing editor for Horticulture magazine. She can be reached at valeaston@comcast.net. Jacqueline Koch is a Seattle-based writer and photographer.