Create interesting window boxes with color, repetition, plant shape

Why are some window boxes so beautiful while others are so blah?

It's all about design, according to Sonia Uyterhoeven, the gardener for public education at The New York Botanical Garden in the Bronx. Choosing and positioning plants with an eye to symmetry, repetition, color, plant shape and size can turn ordinary window boxes into stunners.

Even a mostly green window box with herbs and other edibles can look beautiful if you mix plants with different foliage and shades of green. For a dash of color, add an edible flower or flowering herb.

Here are some of Uyterhoeven's tips.

DESIGN: Common, inexpensive annuals like petunias and coleus are fine for window boxes. But limit yourself to a few varieties and pay attention to the color of the foliage and flowers.

"Avoid the temptation to buy one of everything you see," Uyterhoeven said. "Repetition is crucial in any good window design. Simple symmetry makes it coherent."

A tall plant on one side of a window box, with a flat carpet of blossoms filling the rest of the space, can look unbalanced. A window box that's all impatiens or all begonias "can have a flat look," Uyterhoeven said. "You need different heights to have a successful arrangement: tall, medium and a spill-over."

Consider the "architecture" of the plants, Uyterhoeven said. Some are tall and spiky, some flutter in a soft wave, and some creep or cascade over the side of the box. Think about how the arrangement will look when the blossoms are spent.

"If it's not flowering, does it look bland? If the foliage has different shapes, it will still look nice," she said.

You can give a polished look to any window box by simply alternating upright flowering plants like geraniums with a trailer, like ivy or sweet potato vines, which have soft, pale green, heart-shaped leaves.

COLOR: "Colors change based on what you pair them with," Uyterhoeven said. Green looks paler next to yellow, while you might not notice the red veins in a leaf until you pair it with a red or purple flower.

Bright colors look better in bright sun, while pale colors can fade in sun but look lovely in shade, Uyterhoeven said.

Experiment with color combinations. Red and purple go surprisingly well together, she said.

Other color theory tips: Bright yellow combines well with red and orange; pale yellow combines well with blue. Silver foliage makes blue look more intense, but blue can disappear against dark green.

White reflects light and illuminates shady spots. It also can neutralize loud colors like hot pink, and can separate colors, keeping them from blending or clashing.

MAINTENANCE: Be vigilant about deadheading pansies, violas, petunias, marigolds and other blossoms that quickly fade, and trim plants like coleus and impatiens when they get tall and rangy.

HERBS AND EDIBLES: To make an herb window box visually appealing, mix different shades of green and leaf types.

"In a monochromatic design, the textures and shapes are more prominent than when you have a mix of colors," Uyterhoeven explained.

Consider pale golden oregano, grassy chives, glossy basil, spiky rosemary, creeping thyme, and feathery cilantro, dill and parsley.

Add color by including herbs with pretty flowers, like lavender or sage. Or put edible flowers in the mix, like marigolds, violas or petunias. Another possibility: nasturtiums. Make sure the flowers have not been treated with pesticides, or use organic suppliers at farmer's markets.

Consider other edibles too. A tomato plant called Tumbling Tom "grows just 18 inches high and cascades over the side," said Uyterhoeven. "Swiss chard has a beautiful vase-shape." A type of beet called bull's blood has dark red foliage.

A Latin fusion restaurant in Brooklyn called Barrio grows many varieties of mint in its storefront window boxes. The mint is used in everything from mojitos and specialty cocktails to ceviches and desserts. "We wanted to do something different," said owner Spencer Rothschild, "but we also wanted it be useful."

Inspired, I created two edible window boxes of my own. In one I put feathery cilantro and parsley at each end; basil and a tiny-leafed variety of oregano in the middle; red lettuce in back and spiky lavender on either side.

In my other box, I put a tall sage with purple flowers in the center, purple-veined sorrel on one side, and catnip, dill and more basil (no such thing as too much basil) on the other. In front, creeping thyme tumbles out on the left, with a tangled vine of orange nasturtiums on the right.

My designs are not quite as beautiful as the samples Uyterhoeven showed me. But I used the herbs in dinners three times in a recent week - for pasta, salad and stir-fry. They were bursting with flavor and fragrance. And I can't wait to visit my window box, scissor in hand, for another meal.