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Annuals and Perennials and Shrubs, Oh My!

It seems simple, plants are either annuals or perennials.  Right?  Well, it gets a bit more complicated than that.  Annuals, perennials, shrubs and trees are the most common types of plants, but biennials and temperennials are available too.

Contributors: Kerry Meyer

If you are new to gardening you might find yourself feeling a bit like Dorothy in the Land of Oz.  However, instead of "Lions and tigers and bears, oh, my!" you might find yourself muttering "Annuals and perennials and shrubs, oh, my!"  These three categories do cover many, if not most, of the plants we place in our gardens.  Understanding, the basics of these plant classifications, as well as trees, temperennials/tender perennials and bulbs can help you make the best plant choices for your garden.

Basic, easy to understand definitions are really helpful when trying to learn new concepts.  Let's work our way through these major plant categories, starting with a definition and then adding more information.  Let's start with the three most common categories - annuals, perennials and shrubs.

Annual - A plant that grows, flowers and may produce seed all in one season.  They do not survive the winter.  Annuals must be planted each year.  Many plants we call annuals may be perennial in warmer locations.

Annuals are certainly one of the most common plants you find in garden centers and with good reason. While annuals do have to be planted each year, they also can bloom from planting to frost, in some cases beyond frost, in the fall. Annuals provide consistent color all summer in your garden and are wonderful in containers and landscapes.

Annuals are flexible and since they will be replaced every year can be a good way to try new color combinations.  They can be fun to play with; you can always try something different next year.

At Proven Winners, we select our annuals to thrive in a wide range of environments.  We look for plants that will bloom all summer without deadheading, are disease resistant, colorful and easy to grow. 

Perennial - Plants that are cold hardy and will return again each spring.  Some will flower the first year they are planted and some will need to mature before flowering.  Some perennials are very long lived and others will survive only a few years.

Perennials are in many ways the flip side of annuals.  Most perennials will bloom for a limited period of time, a month to six weeks is common, whereas annuals will bloom all summer.  Annuals are planted every year, whereas perennials are winter hardy and will add color to your garden for many years. While perennials can be used in containers, they are almost always used in the landscape.

There is some maintenance involved with perennials.  Fall clean-up is necessary for plant health.  Many perennials also benefit from regular division(usually every 3-5 years,) which means you dig them up, divide the perennial clump into several pieces and then replant.  Over time the perennials you buy can be spread throughout your garden.  Perennials can be moved in your garden relatively easily.

Perennials are a good way to add early spring color, when annuals aren't yet established in the garden.  Aubrieta, creeping Phlox and Iberis are all good examples of perennials that are used in this way.

Shrub - A woody plant that has multiple stems and branches at or near the ground.  They are relatively small, especially when compared to trees.

Shrubs are fairly permanent elements of your garden.  They are either deciduous, which means they go dormant and lose their leaves in winter, or evergreen, which means they don't go dormant and do retain their foliage all winter.  Shrubs are one of the main ways to add structure to your garden, sometimes called the bones of the garden.  Shrubs, even deciduous shrubs, maintain presence in your garden when perennials are dormant and annuals are dead.

Some maintenance may be required for your shrubs.  Some will need pruning and deadheading can sometimes extend bloom time.  Shrubs can be moved in your garden, but this is much more difficult than it is with perennials.

Evergreens are especially good at adding winter interest to your garden.  They also can provide cover and forage for wildlife.

The work of plant breeders is starting to transform the role of shrubs in the garden.  For instance, Proven Winners ColorChoice shrubs are selected to provide multiple seasons of color to your garden.  Colorful foliage, longer bloom periods, interesting bark and unique forms are just some of the ways this is happening.  Old standards are being reinvigorated.  If you think shrubs are boring, take a look at some of the new items that are coming on the market.

Now that we've covered the big three, let's talk about other plants you may encounter.

Temperennial/Tender Perennial - Plants that are perennial in warm locations, but are not winter hardy in cold locations.  These plants are often treated as and called annuals in cold climates or may be in the house plant section in a garden center. 

This can be a confusing category. Things that you may be absolutely certain are annuals, may actually be temperennials.  Here is a good example; you are probably familiar with New Guinea Impatiens, double Impatiens and bedding Impatiens.  They are extremely common annuals for shade.  Well, if you were in New Guinea, or the mildest winter climates in the US, these plants would be perennial.  They are in fact tender perennials.

Now, if you get right down to it, the label given the plant isn't important.  What is important is how the plant performs in your garden.  You don't really need to care what the plant is called.  I know I think of Impatiens of all kinds as annuals, despite knowing that isn't what they truly are.  In my garden and most of your gardens, they function as annuals.  This is why we call these plants annuals.  They fill the function of annuals for most North American gardeners.

If the label isn't really important, you might be wondering why I even mention it.  It is important because for some of you the plants we (and many others) call annuals might actually be perennial.  To learn if the "annual" you are looking at on a website is an annual for you, you need to compare the plants hardiness zone to the zone in which you garden.  I covered this topic extensively in the article Zoning in on Hardiness.

Tree - A woody plant with a single stem and branches that begin some distance from the ground.  They are relatively large, especially when compared to shrubs.

Trees are the most permanent members of your garden and if you are adding one, or more, of them choose carefully.  It can be hard to look at a small tree and envision it being 30 feet tall and wide, but it is important to make sure you evaluate your space and choose a tree that fits.  Trees come in a huge array of sizes, shapes and characteristics.  Take the time to explore and choose the right tree for you needs. 

Trees are very much a long term investment and it will be well worth spending the time and effort up front, to make sure you don't regret the decision later.

Bulb - Bulbs have a very specific definition, read it here, but most of us use bulb as a general term to refer to bulbs and bulb-like structures (corms, tubers and rhizomes.)  These plants grow from an underground storage unit of some type. Bulbs can be both hardy and non-hardy.

Hardy bulbs (I will use bulb to mean bulbs, corms, tubers and rhizomes) are bulbs that will survive the winter.  Most of use probably think of early spring color first when we think of hardy bulbs.  Daffodils and tulips have got to be the most popular and common choices.  I know I wouldn't want a garden without daffodils!  There are, of course, many other hardy bulbs and they can be wonderful long term additions to gardens.

Non-hardy bulbs will not survive the winter in the ground, but must be dug and stored for the winter.  Once warm weather has returned they can be planted again for the next year.  Or you can let the plants and bulbs die and buy new again the next year.  You won't get in trouble for plant homicide if you prefer to not worry about digging and storing. Some of the most common non-hardy bulbs include canna lilies, elephant ears, gladiolus and dahlias. 

Non-hardy bulbs are similar to tender perennials/temperennials.  They are hardy somewhere.  Head to Florida and elephant ears are permanent plantings!

For more easy to understand definitions of horticulture terms, click here.

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