Plant Life Cycles and Garden Design

By Ann Whitman, Suzanne DeJohn, and The National Gardening Association from Organic Gardening For Dummies, 2nd Edition

9 of 12 in Series: The Essentials of How to Plan a Garden

The life cycles of all the plants you choose for your garden play a large part in the garden's overall design. A plant's life cycle consists of the amount of time it takes for them to become mature enough to bloom, produce seed, and ultimately die. Depending on the plant, your garden design can focus on color, form, or foliage.

Plants belong in one of three categories: annuals, biennials, and perennials.

Annuals: Annuals complete their life cycle in a single growing season. They typically sprout from seed in the spring, bloom, produce seed, and die before winter comes again. With proper care, most annual flowers will bloom continuously all summer, right up until frost.
If you want the most bang for your buck, flowerwise, choose annual plants. Most garden vegetables and many herbs are annuals (or we treat them as such). Because they die in fall, annuals must be replanted every year.
Biennials: Biennials live for two growing seasons. In the first year, they sprout and grow leaves and roots. The flowers and seeds come in the second growing season, after which the plant dies. Biennials are relatively uncommon in home gardens.
Perennials: Perennials live for at least three seasons, and many live much longer in the right climate (in the wrong climate, they act more like annuals). Perennials can be herbaceous, those with stems that die to the ground in the winter and grow back from their roots, or woody, those with tough, persistent stems or trunks (think trees, shrubs, and woody vines). Woody perennials create a backdrop for other plants, and provide habitat for wildlife.

Perennial flowers tend to have a distinct bloom period lasting several weeks, although some flower sporadically throughout the summer. By choosing a combination of early-, mid-, and late-season bloomers, you can have continuous color as different flowers bloom and fade.

Plants are also characterized by whether they keep their leaves year-round, and they fall into these categories:

Deciduous plants: These plants grow new leaves each spring. In autumn, those leaves die and fall off, leaving branches bare until spring.
Evergreen plants: These plants keep their leaves year-round. Although most shed leaves occasionally, their branches are never bare.

Following are two examples of evergreens:
- Needled evergreens, which include pines and spruces. (Think Christmas trees.)
- Broadleaf evergreens, which have non-needle-like leaves. This category includes rhododendrons and most hollies.
Some herbaceous perennials, such as candytuft and hellebore, are evergreen. Others, such as bearded iris, are evergreen in warm climates and deciduous in cold climates; plants like these are sometimes described as semievergreen. And sometimes varieties of the same plant differ ¯ evergreen and deciduous daylilies, for example.
Conifers: Conifers are plants that bear cones. Although most conifers are evergreens, exceptions occur. One exception is larch (also known as tamarack), which is a conifer that loses its needles and is known as a deciduous conifer.

Whether a plant drops its leaves is an important consideration in garden design. If you want a year-round screen between your home and your neighbors, make sure that the plants you choose are evergreen. To find out which of these categories a plant fits into, read plant descriptions carefully; don’t make assumptions based on generalizations; and try to find information specific to your gardening climate.