Last Build Date: Fri, 17 Feb 2017 14:09:27 UTCCopyright: Copyright 2017
Thu, 29 Dec 2016 14:44:33 UTC
So-called "annual" flowers die at the end of each growing season. But some of them are ones that would live for years if we didn't have an inconvenience known as freezing weather.
Q: I got a white-blooming euphorbia in 2008 that was sold as an annual flower. Each fall, I've dug it up and kept it in my bathroom over winter, and it's been getting bigger and bigger every year. Some years it trails 5 feet.
I've kept petunias going for nearly 20 years and read that it's really a tropical perennial. Is that the case with this euphorbia? It doesn't seem to meet the botanical definition of "annual" to me.
A: The designations "annual" and "perennial" aren't commonly used as hard-and-fast botanical definitions but labels we give to plants to describe whether they're going to make it through more than one season in a particular climate.
That can vary from place to place. In frosty winters like ours, petunias and that euphorbia of yours are classified as annuals. When you let them outside, they normally die when our first freeze comes along in fall.
They're acting like "perennials" because you've protected them from the factor that makes them an annual here - i.e. sub-freezing cold.
Move those same plants to a frost-free environment, and they can live multiple years. In other words, the same euphorbia that's an annual for us is a perennial in southern California.
Technically, there's a difference between "true" annuals and ones that act like annuals in a particular climate. "True" annuals are ones that go through their entire life cycle in a single year no matter where they're growing.
Examples of those are marigolds and zinnias. Flowers that are annuals for us but perennials in frost-free zones include geraniums, begonias, impatiens, snapdragons and coleus in addition to the petunias and euphorbias you mentioned.
By definition, a perennial is a plant that lives more than 2 years. A plant that produces vegetative growth the first year, seeds the second and then dies... that's a biennial.