Let’s start at the beginning. True annual plants have short lives. They make colorful displays because they need to produce as many flowers as they can as fast as they can because they are going to die at the end of the summer. A few annuals, such as pansies, do prefer cooler weather and will do better in spring or fall plantings. Annual plants are actually trying to produce as many seeds as possible, so we will sometimes need to remove dying flowers by deadheading to prevent seed production and promote more flowers.
Garden perennials are long-lasting plants that come up each spring from underground storage structures such as bulbs, tubers, and roots. Technically, perennials don’t have to bloom for many years, but the ones we grow in our gardens do bloom each year. They must be carefully placed in the garden because they won’t be going anywhere for a long time. They need good soil conditions before they go in. The better the soil, the better the plant will do. Shrubs and trees are also perennials, but they don’t die back to the ground in the winter.
Biennials live two years. In the first growing season, they produce leaves and roots. In the second year, they produce flowers and seeds. Hollyhocks and some foxgloves are the two most common biennial garden flowers, but there are others. Most biennial vegetables are treated as annuals and grown for leaves and roots, such as cabbage, carrots, lettuce, parsley, and radishes. The biennial herb caraway is grown for the seeds it produces in the second year.
Many biennials and perennials are used as annuals. Some of these perennials are actually trees or shrubs from tropical locations. This is especially true for container plantings. In the summer, just about every plant can grow outdoors. But in the fall of cold climate zones, tropical perennial plants will get too cold to survive unless they are brought indoors.
There are thousands of species of annuals and perennials available to the gardener. There are many North American native prairie, wetland, and woodland plants used in gardens, plus there are more species from across the globe. The middle of Asia, parts of Africa, Australia, Europe, and South America all have regions that have a similar climate to parts of North America. Plant explorers have brought plants from all of those regions to be used in our gardens.
Like I said, perennials need good soil because they are not going to move. Annuals should be moved on a regular basis. At the end of the season, annuals are uprooted and thrown in the compost pile or garbage. However, some leaves, stems, and roots remain in the soil. Decay and disease organisms can build up in the soil by feeding on these leftovers. By planting different kinds of plants from different plant families in the garden, disease organism populations are reduced.
