Heat-Tolerant Plants for a Window Box

Succulents

• Succulents are evergreen plants with shallow root systems and thick leaves. A succulent's leaves act as water storage, allowing the plant to endure long periods without access to water. Small cacti, such as astrophytum and sempervivum are two examples of succulent plants for window boxes. Succulents require full sunlight for growth, so place succulents in a window box where they receive maximum exposure to the sun.

Annuals

• Plants with a one-year lifespan are annuals. Gardeners plant annuals in the spring for summer blooms. Most annual flowers blossom from June through August before frost arrives in the autumn. Some drought-tolerant annuals are geranium, nasturtium, California poppy and marigold. Most of these flowering annuals grow under a foot tall, making them suitable to a window box's limited space. The tallest of these plants, California poppy and nasturtium, are approximately 12 inches high.

Perennials

• Perennials are plants with a potential lifespan of more than one year. Some perennials are herbaceous, meaning their stem wilts to the ground during the winter, or have woody, upright stems. Tickseed, cheddar pinks, cone flower, evening primrose and lavender are perennial flowering plants with a high drought tolerance. These plants will not overcrowd a window box because they grow between 1 to 2 feet tall.

Vines

• Also known as trailing plants, vines depend on outside structures for support. Gardeners plant vines in window boxes with the intent of the plants hanging over the edge of the box. Some drought-tolerant vines are flowering plants such as black-eyed Susan vine, morning glory and hydrangea. However, gardeners must prune vines to prevent them from growing too rapidly or climbing the building. Annual and perennial vines are available.

Herbs

• Most herbs have a high drought tolerance and maintain their fragrance even after drying up from excessive heat. Herb plants are grown for ornamental, medical and culinary purposes. During the winter, herb plants live longer if protected; an herb's shallow roots are susceptible to spring thaw. Some drought-tolerant herbs are oregano, rosemary, thyme and mint.