When talking to new gardeners, the inevitable question always comes up; that is, "what is a perennial?" They seem confused.
Some people know them by their simple definition; that is, a perennial is a plant that comes back every year. This is different than annuals that die once the growing season ends and need to be replanted every year. While this is true, sometimes confusion comes in because like most things in gardening, it's not that black and white.
For more information and to read about the differences between annuals and perennials, read our article here.
For now, we want to clear up any misconceptions you might have about what is a perennial and to do that, it's helpful to know what's actually happening with the plants.
When perennials "die" at the end of the growing season they don't actually die. Yes, the part above ground (the flowers and foliage) does die, but the roots actually go dormant for the winter. Once the soil warms in spring the roots come out of dormancy and start growing once again. This means that perennials can last for many, many years and keep blooming year after year. It's the gift that keeps giving.
This cycle repeats indefinitely, or until the plant roots actually die.
Understanding this process is the key to knowing the answer to the question of what is a perennial. If you have any doubts about any plant, find out about what's actually happening to the plant when it dies and you'll know if it's a true perennial.
Confusion can arrise though because the same plant can be an annual in one part of the U.S., and a perennial in another part. In addition, sometimes what you thought was an annual keeps coming back year after year. This makes you wonder if you were wrong thinking it's an annual. Then it one year, it doesn't come back at all, throwing your judgement into a tailspin!
What's a person to do? Actually, know what's happening with the plant.
All plants are hardy down to certain temperatures and with current weather patterns changing, conditions in your back yard may not always fit into the planting zone chart you've come to know and love. This means that the growing patterns of plants are getting harder to predict. Nature is not always so cut and dry. Who knows. Perhaps in one hundred years, the planting zone chart will need to be changed!
That's why it's important to know 2 things:
In which planting zone you live.
The hardiness of each plant in your garden.
This will give you a good guide or rule of thumb when it come to deciding which plants in your area are considered perennials. Just know that sometimes these rules will be broken.
Perennials Are Not Just Flowers
It's also important to note that when we speak of perennials, we're not just talking about flowers. Sure there are many perennial flowers such as cone flowers, coreopsus, dyanthsus, daffodils, etc. but there's much more to the plant category.
There are also perennial shrubs, plants that don't usually flower or at least are not known for their flowers. Take for instance the very common hosta plant.
There are a huge variety of hostas on the market today, each with different shades of green leaves, both solid and varigated. This is their main draw - their wide variety of color and the size of the leaves.
However, hostas also flower - usually later in the summer. Did you know that?
The flowers though are really an after thought. No one that we know ever buys hostas for their beautiful flowers. They buy them for the foliage.
There are other perennials that are bought for their leaves. Coral bells, lambs ear and loriape are just a few.
Exceptions To The Simple Question Of What Is A Perennial
As the saying goes, some rules are made to be broken. Nowhere is this statement more appropriate than in gardening and landscaping.
Here are examples of when some of the rules governing perennials may not always hold true.
Example 1- Sowing The Seeds:
Some plants might "seem" to come back every year when in fact they don't come back from the roots. For example, sunflowers, actually re-seed themselves by dropping seeds during the growing season that germinate the following year.
Other plants do this as well.
This is not to be confused with other perennails that multiple from the roots. That is, the roots spread through the ground and new plants sprout up at other spots along those roots.
Example 2 - Bad Behavior:
Flowers such as tulips and daffodils do not grow from seeds at all, but instead, grow from bulbs that DO come back each year. Therefore, they are considered perennails.
However, some people treat tulips as annuals and plant them every year. Why? I'm glad you asked. Inquiring minds want to know!
Daffodils are very reliable. They are easy to grow and come back every year without any effort and often muliply - exactly what you'd expect of a perennial.
Tulips however, are not so easily grown. Yes, they will come back as well, but they don't always do well in subsquent years; that is, year 2 will be a little worse, year 3 will be a little worse still, etc. In fact, for many people, this problem means they treat tulips as annuals, planting new bulbs every year.
Tulips can be finickly. Ideally, in their native countries of eastern Turkey or the foothills of the Himilayas, they act like a normal perennial, coming back every year and multiplying. Here in the U.S. many people's back yards are not ideal for growing tulips, so they don't do as well as in their native regions.
That's why you'll often see people digging up old tulip bulbs every year and replanting new, even though they do come back.
Pros do this as well. Clients usually want beautiful gardens every year without fail so for them, planting new tulip bulbs every year is mandatory.
Example 3 - Weather Wows:
Some annual plants that usually die will come back year after year in the right conditions. That means if you have 2 abnormally warm winters, you might have some plants known to be annuals coming back, acting as perennials.
Or perhaps your planting location is next to concrete, which radiates heat, or is protected from the cold by a fence or a wall. This may cause plants that are considered annuals to come back every year as well.
I mention this because one of our clients has this exact situation. She has blue agoratum planted next to a concrete porch wall and sidwalk. Even though blue agoratum is normally an annual for us, her plants come back every year.
We've had other situations like this with various plants in our clients gardens. So it is with nature. Our advice is... always expect the unexpected. You could be pleasantly surprised.
The Revelation - What Is A Perennial?
As you can see from these examples, the question can be answered easily. It's a plant that comes back every year. In reality though, the plant world likes to make it more complicated.
Fear not, this simple definition will always hold. It's the plants that don't seem to know this and sometimes make their own rules.
The good news is you don't have to study each and every plant's growing hardiness and know it intimately.
If you've lived in the same area all your life, you've probably become familiar with which plants are annuals in your area and which are perennials. If you don't know, your local garden center will have the answers.
Shopping for plants is one of the best ways to get familiar with plants and their hardiness in your area. That way, you'll be able to answer the question "what is a perennial" with certainty that you know the answer.