Gardening enthusiasts, especially novices, may be a bit confused about the differences between annual plants and perennial plants, and may not have even heard of biennial plants. Understanding the distinctions between these three types of plants will enable you to create a thriving garden that rises to your expectations, satisfying both your aesthetic and maintenance preferences year-round.
Let’s delve into the fundamental differences between annual, perennial, and biennial plants, highlighting their unique characteristics, benefits, and things that you may want to consider when planning and planting your garden spaces.
The Basics of Flowering Plant Life Cycles
All flowering plants follow the same basic steps in their life cycle. Annuals complete their life cycle in one single growing season, while perennials live on for three years or longer; sometimes flowering for decades. Biennials have a life-cycle in keeping with their name. Their biological life cycle usually takes two years to complete, while combining characteristics of both annual and perennial plants. However, as you dig deeper into plant labels and descriptions, you’ll find many nuances to these basic definitions. Terms like “hardy” and “half-hardy” annuals or “tender perennials” often appear, adding complexity to your choices when making your plant selections.
What is clear is that when comparing annuals to perennials and biennials to both, there is not one that is superior to the other. Integrating all types of these flowering plants into your garden design (along with shrubs and trees) provides unlimited options in color, texture, form, flowering time, and even maintenance.
What is an Annual?
True annuals are plants that germinate, flower, set seed, and die all in one solitary season. Their ultimate goal is to reproduce themselves (set seed), which is good news for gardeners because most annuals will flower like mad until their mission is accomplished. If you use methods such as deadheading to prevent seed formation, many annuals will ramp up their flower production and continue to bloom profusely until the first frost arrives. Although you’ll need to replace or replant most annuals the following spring to get a repeat performance, some will readily self-sow and return for an encore; Sweet Alyssum, Bachelor’s Button, and Forget-Me-Nots are just a few examples of self-sowing annuals.
Types of Annuals
Not all annuals are created equal. Annual plants are typically subdivided into three groups:
- Hardy or Cool-Season Annuals: Such as Forget-Me-Not and Larkspur, thrive in the cool to moderate temperatures of early spring and mid-to-late fall and can tolerate exposure to light frost without being protected.
- Tender or Warm-Season Annuals: Two examples are Marigolds and Petunias which are native to tropical or subtropical climates and require heat to grow and thrive. They often grow poorly during cold weather and should be planted in late spring.
- Half-Hardy Annuals: These plants fall in the middle of the temperature tolerance spectrum. They tolerate a wide range of temperatures, including periods of cooler weather near the beginning or end of the gardening season.
Why Choose Annuals?
- Experimentation and Imagination: Growing annuals can be a great way to take gardening one year at a time; you can experiment with new plants and color schemes without making a long-term commitment, and then change it up each year if you choose.
- Instant Gratification of a Temporary Nature: Annuals are perfect for temporarily filling in bare spots in established gardens or refreshing containers throughout the season. Annuals provide nearly instant gratification, maturing faster than perennials or biennials, and often blooming non-stop from planting time until frost, and in some cases beyond.
- Pollinator Attraction: Add annuals to a vegetable garden for a splash of color, to fill in gaps when early-season crops are harvested, and to attract pollinators to increase your production of edible crops. Don’t have a vegetable garden? Just plant annuals for the joy they bring!
- Abundant Blossoms: If flowers are what you want, then flowers are what you’ll get when you grow annual plants. They put all of their energy into developing flowers.
Biennials: The OTHER Perennial
Biennials take two years to complete their growth cycle before dying. Usually, biennials do not bloom until their second year, though some behave like short-lived perennials and will flower their first year when planted early enough in the spring or when started indoors in winter. Biennial plants typically spend their first year producing their root structures, stems, and leaves. During their second season, biennials will favor you with the formation of flowers and seeds. Seeds? Yes! You do not have to buy new biennial plants each year. Simply harvest the seeds to plant next year. Successive plantings will result in biennial blooms every year! In colder climes, biennials are often treated as an annual plant. Some examples of biennial plants are:
- Dianthus—Dianthus is sometimes known as “Pinks”, though that name is not so accurate any longer. Creative breeding has resulted in red, salmon, and bicolored varieties, in addition to the many pink choices. Dianthus have a spicy scent, similar to cloves.
- Foxglove—This biennial plant is also known as Digitalis. Foxglove will grow with just 4 hours of sunlight daily, so are ideal for partially shaded areas. Their bell-shaped blossoms grow on tall flower spikes, blooming from the bottom up. There are a number of pleasing color choices, all with their signature spotted throat. Foxglove will self-seed every year, so it is sometimes confused with a perennial plant, as it grows back each season.
- Hollyhock—Hollyhock is known botanically as Alcea. Its impressive stems of flowers can reach up to 8-feet tall and may require support in particularly windy areas. Not only are they strikingly beautiful, they serve as a pollinator buffet, attracting butterflies, honey bees, and hummingbirds, all essential to food crop production.
What is a Perennial?
Unlike their shorter-lived counterparts, perennials are typically cold-hardy plants that will return again the following spring. They usually bloom for only one season each year (either spring, summer, or fall), but there are also reblooming and long-blooming perennials, such as Fern-Leaved Bleeding Heart (Dicentra ‘Luxuriant’).
When grown in favorable conditions, perennials often live a long time, but don’t assume they will last forever. Their life span is variable, and some may live for only three to five years, while some perennial plants may live much longer. Some examples of perennials that can live for decades are:
- Peony—This long-lived perennial bloomer can grow up to 3-ft tall depending upon the variety. They will multiply by reproducing new bulbs, so a single Peony this year may surprise you with 3 or 4 next year! There are Peonies of about every color imaginable.
- Daylily—It is possible to completely naturalize your landscape with Daylilies! Plant a few and wait for the magic to happen as they reproduce bulbs and keep on growing and spreading, year after year. They are tough and require hardly any care, except to divide them every few years to keep them blooming. Even if you don’t divide them, the plant will continue to live displaying its lush foliage.
- Hosta—This shade-loving perennial plant is readily available with a myriad of leaf shapes, patterns, sizes, and textures. Hostas send up new plants throughout the growing season by way of rhizomes (basically, an underground plant stem that grows horizontally). When your Hostas have filled the space they’re in, you can divide the plants to plant elsewhere or to give to friends and family. Hostas bloom, though gardeners grow Hosta plants for the foliage.
Perennials also vary greatly in terms of their care and maintenance. Some may need to be pruned and divided regularly to maintain their vigor and keep them tidy, while others are tough and undemanding, seeming to thrive on neglect.
Why Choose Perennials?
- Long-Term Investment: Although perennials tend to cost more initially, they are a good long-term investment because they return year after year.
- Propagation: Even perennials that don’t have a long life span can often be propagated by division or reseeding to perpetuate their population.
- Water Efficiency: Most perennials require less water once established, which can be especially advantageous for those who garden in drought-prone areas and want to reduce their water consumption.
- Native Plant Benefits: Planting perennials that are native to your region will provide the additional benefit of creating a welcome habitat for pollinators and local wildlife.
Integrating Annuals, Perennials, and Biennials in Your Garden Spaces
Combining annuals, perennials, and biennials in your garden design will result in a diverse and dynamic garden landscape. Annuals provide continuous, season-long color and the flexibility to experiment with different styles each year. Perennials, on the other hand, form the backbone of your garden, offering stability and returning year after year with minimal maintenance. Biennials, have their roots in both worlds! By understanding the unique characteristics and benefits of all three plant types, gardeners can create a beautiful, resilient, and ever-evolving garden that thrives throughout the seasons.
