Perennial, Annual, Biennial, Hardy, Half Hardy and Tender. What does it Mean?

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Every year, just after the holidays, we start to see seed catalogs pour in our door.  Every year, we also start to see e-mails and messages asking what the terms found in them mean.  This year, we thought we would make it easier for everyone and post an explanation of what perennial, annual, biennial, hardy, half-hardy and tender mean.

 

Perennial

A perennial is a plant that has a life cycle of more than 2 years. Many perennials can live a very long time if cared for properly. Some are called short lived because they may only survive 3 to 5 years.

 

Annual

An annual is a plant that completes its life cycle from seed to seed, then dies, in the span of one season. A plant is not an annual because it freezes in your climate, it is only called an annual if, in it’s natural habitat, it completes its life cycle in one year. If you plant annuals, you will need to plant each year, and some will reseed themselves. One of the most common plants miss labeled as an annual is snapdragons.  They are actually perennials if grown in zone 8 or warmer, and should be labeled as “grown as annual” to avoid confusion, but is often just called an annual.

 

Biennial

A biennial is a plant that requires 2 seasons to complete its life cycle. The plant establishes itself the first year, then flowers and sets seed the next.  Great examples of biennials are Sweet William and Foxglove.  Every year our local nurseries sell Foxglove and label it a perennial. These plants are in full bloom.  If I see someone holding the plant I inform them that it will not bloom for them next year and explain.  If it’s a true Foxglove (Digitalis purpurea)  the plant will set seed after flowering and die because it is in it’s second season.  Some plants like Hollyhocks are biennials that are grown as annuals.  If you plant them early enough in the season, or even indoors before last frost, they can complete both cycles before the snow falls but will not come back the next year unless it self sowed.

 

Those terms are to explain a plants life cycle, the next are to help guide planting times, although in mild climates, the terms really are meaningless and many sources don’t even use them.

 

Hardy

A hardy plant is one capable of surviving outdoors in a particular climate with no protection. It can survive some frost without being killed or badly damaged.  Hardy annuals include calendulas, cornflowers, sweet peas and nasturtiums.  These plants can be safely sown outdoors early in the season, or in some cases, depending on exactly how cold it gets in your zone, at the end of a growing season to over winter in the soil

 

Half-Hardy

A half-hardy annual is one that will grow outdoors during the summer but can’t be transplanted or directly seeded outside until all danger of frost has passed.  Most can handle long periods of wet and cold weather, but frost will usually kill them.  Some examples are marigolds, petunias, and nemesia.  Some plants grown as half hardy annuals are actually half hardy perennials like geraniums and snapdragons. Rarely are they labeled correctly.

 

Tender

A tender annual can’t be transplanted or directly sown into the garden until the soil is warm.  They require, warm days for good flower production.  These plants usually need to be started indoors in colder climates.  Heliotrope is often called a tender annual.


Using these terms incorrectly only causes more confusion.

One of my pet peeves is hearing “it’s an annual in my zone”.  A plant is either a perennial, or an annual, it isn’t both.  It can be said “it’s a perennial, but not hardy in my zone”, because you are still stating it is a perennial, but you can't grow it for it's lifecycle where you live.

Using these terms correctly is extremely important in the gardening world because plants can mean different things to different people.  I had a dear friend pass away who adored geraniums. When inquiring about keeping one of her flowers as a reminder of her, I was informed they let them all die because they thought they were annuals and didn’t know they could be over wintered.


It’s important to note that some seed companies use these terms without any steadfast meaning to them. Always do a little extra research when shopping for a plant as many nurseries try to fool you to make an extra dollar.  This past year I say a beautiful passiflora being sold as a perennial at our local nursery.  This was correct, but they did not have it labeled as not being hardy here in Minnesota.  I am certain many gardeners planted it and were sad to discover that it didn’t come back in the spring.  A $40 plant with no money back guarantee.