Window boxes need no introduction. Picture the classic eye-catcher: a narrow box painted perfectly to match the house trim, abundantly spilling forth ivy geraniums, pansies, and petunias. You can come across plenty of these old-fashioned favorites embellishing gingerbread houses or jazzing up everything from a ranch-style home to a city flat.

Window boxes, of course, are just containers attached to the house. They're easy to plant. Here are some key points to keep in mind to help you choose, plant, and care for a window box:

Select a style that matches your house. Treated softwood or hardwood boxes are easy to paint or stain to blend in beautifully with their surroundings. Plastic, metal, terra-cotta, or concrete boxes can work too, but are harder work with.

Pay attention to size. A window box looks best if its length is within a couple of inches of the size of the window, although slight differences — long or short — won't hurt. Plants need room to grow and soil that doesn't dry out too fast — boxes should be at least 8 inches wide to provide room for top growth and 8 inches deep for the roots.

Make your own box if your window is oddly sized. Use 1-inch boards and simple joinery with waterproof glue and galvanized or brass screws to secure the pieces. Drill several drain holes along the bottom.

Go for a sunny exposure to please the most plants. This, though, increases your watering chores. Remember that some window boxes are protected from rains, so you need to check regularly for dryness. Don't worry if there's shade. Many excellent shade plants thrive in partial or full shade.

Position the box below the window by a few inches. If you happen to have a window that opens outward, you have to lower the box. Use steel brackets every 18 inches or so and fasten them into the siding or masonry with the proper screws. Rest the box on the supports and screw the bottom to the brackets. Always mount the box before you plant.

Planting and caring for your window box

You have three options for planting your window box:

Plant directly in the container.

Drop in potted plants and fill around them with moss, bark, or another lightweight material.

Put plants in a plastic or metal liner that fits inside the box. With this method, you can rotate liners and add fresh plants when current plantings pass their prime.

Basically, you plant the same way you do in any container. Cover the drain holes, fill with soil mixture, and firm soil around plants, leaving at least 1 inch at the top for watering. Use routine good care on the window box, starting with regular watering, feeding with a liquid fertilizer, and grooming to remove faded flowers and leaves.

Picking the (plant) winners

Choosing a container and a location is a fine start for window box gardening, but picking the right plants really makes the difference in your growing success. Generally, select a mixture of trailers, compactupright plants that grow tall enough to be seen without blocking the window, filler plants, and bulbs.

For a dramatic display, choose plants that contrast with the background — bright plants against light siding or wood, pale flowers against dark brick walls. Here's a brief rundown of the top 12 plants — both annuals and permanent ones — for window box culture. But remember that this list is intended only to get you started; your plant choices are many and varied for dynamic window boxes.

Annuals

Sweet alyssum: Stalwart, reliable, fragrant trailer in white, cream, pink, and purple. Alyssum is exceptionally easy to grow and fills in beautifully, often reseeding itself.

Lobelia: Sound familiar? Yes, we often call on this little annual with clouds of cascading color in white, sky blue, dark blue, rose, lavender, and cobalt. Simply great in window boxes.

Pansies: Perfect in any box, pansies offer prolific color in many hues and quickly fill gaps between permanent plants or other annuals, offering long-lasting color.

Petunias: Choose these when you want a stunning summer box that shines in the sun. Try cascading varieties, as well as multifloras, for an abundance of blooms in a wide range of colors.

Impatiens: The plant for shade, and awesome in window boxes — especially valuable for continuous color in a range of hues. Use low-growing, dwarf varieties. New Guinea hybrids also offer excellent foliage.

Dianthus: You get the bonus of fragrance with the gift of color. Plants are well behaved. If all goes well, a breeze blows, sending sweet scents through your open windows.

Permanent plants

Ivy geranium: Yep. The selfsame winner in hanging baskets, this one also works really well in window boxes, gracing us with wonderful trailing stems covered with bright flowers. In cold climates, grow it as an annual.

Geraniums: Bedding geraniums are the classic window box plant — grown for clusters of brilliant flowers in colors ranging from white to crimson to apple blossom pink. Plants are easy to grow. Consider geraniums an annual in cold climates.

Dwarf bulbs: Forgive us for lumping so many bulbs together, but the miniature nature of many flowering bulbs — daffodils, crocus, grape hyacinth, cyclamen — makes them ideal players in the window box.

Ground ivy: Impressive long stems spill from your window box in shimmering green or variegated tones. Ground ivy can survive through winter in milder climates.

English ivy: Hardy, versatile, attractive, and useful for any box where you want trailing plants, ivy handles in sun or shade. For extra color, choose varieties with cream or yellow accents on the leaves.

Miniature roses: You have dozens to choose from, and each one can be trusted to perform elegantly and effectively in combinations with annuals or other permanent plants. Some varieties also offer fragrance.