Window boxes add a splash of color to the exterior of buildings. These planters also allow apartment dwellers and others without access to a lawn or garden to raise flowers, herbs and even vegetables. Plants in window boxes need regular feeding to thrive and should be watered daily in dry weather. You can add water soluble crystals to retain water around plant roots, or choose a self-watering planter with a reservoir. Use a potting mix designed for planters.
Choose plant varieties for window boxes with fairly shallow roots. Most window boxes aren't deeper than 1 foot, and many are even shallower than that. Herbs do well in window boxes, as will annual flowers such as geraniums, petunias and alyssum. If you want to grow vegetables, opt for lettuce, green onions, baby carrots or radishes. Most tomatoes require more soil than window boxes offer, but you can grow patio, cherry or grape tomatoes in deeper window planters.
The house to which the box is attached will shade your window box at least part of the day, and nearby trees or other structures may provide more shade. Flowers such as begonias, pansies and impatiens and greenery such as variegated ivy will do well in partial shade. For vegetables, stick to greens such as lettuce, spinach or chard for heavily shaded boxes and dwarf varieties of peppers and patio tomatoes for sunnier spots.
For the best impact from the street, choose trailing plants for your window garden and combine colorful flowers with green vines. Mix trailing petunias with variegated ivy. Or plant a herb garden with rosemary, sprawling oregano, different colors and varieties of basil and nasturtiums.