“Annual” and “perennial” are words that gardeners throw around all the time. If you are new to gardening, you may have nodded your head along to the lingo without being certain of the difference between the two. But what do these terms mean?
At the most basic level, an annual plant completes its life cycle of germinating, maturing, producing flowers or fruit, developing seeds and dying within the year. There are both winter annuals, which start this cycle in the late summer and die by the spring, and summer annuals that go through the same process in the summer months.
“Both types of annuals have a ‘live fast and die young’ approach to allocating their resources,” said Kate Garland, horticultural specialist at the University of Maine Cooperative Extension. “In other words, annuals are more likely to flower earlier and typically have a less robust root system.”
Perennials, on the other hand, live for many seasons. As such, they dedicate more of their resources towards establishing their vegetative, non-reproductive structures, especially their root system. The plants can be woody like trees and shrubs, or herbaceous. Perennials that Mainers might recognize include rhubarb, asparagus, maple trees, blueberries, cone flower, phlox, rhododendron and thyme.
The difference between annual and perennial plants is based on the genetics of the plant, either through evolution or breeding. However, the distinction between annuals and perennials is not black and white — it’s more of a spectrum.
Roughly between the two are biennial plants, which germinate; set out leaves, stems, roots the first season; overwinter; and, finally produce a flower, fruit and seed the following year before they die.
“People are often surprised at some of the common vegetables that are biennials [like] carrot, onions, beets,” Garland said. “These all have a solid root system and aren’t plants we think of as flowering plants because we rarely give them a chance to flower. We usually harvest them the first season before they have a chance to overwinter and produce those flowers.”
There are crops that will behave as either a perennial or annual depending on how and where they are grown.
“Peppers, basil, perennials we grow as annuals [but if] you go further south and they just keep growing [and] turn into shrubs,” said Caleb Goossen, organic crop and conservation specialist at the Maine Organic Farmers and Gardeners Association. “Some people try to stretch the limits of what they can grow as a perennial here. Some folks can grow lavender outdoors many winters [by] protecting it somehow. Herbs like oregano can be like that, [too].”
Some common crops hover between categories.
“Onions are a great example of a group of plants that have different species or varieties with different life cycles,” Garland said. “Most of our traditional edible onions are biennial, but there are certainly a number of perennial onion family members, such as chives and walking onions.”
When choosing whether you want to plant annual or perennial plants, consider the long-term goals for the space. For crops, it takes time to get most edible perennials established enough to enjoy the “fruits” of your labor, so most gardeners opt for primarily annual crops.
“For example, asparagus harvest should be delayed until the second year after planting crowns; you wouldn’t want to have to reset the clock and wait another two years to harvest asparagus because you didn’t select the right spot for it in the first place,” Garland said.
For ornamental crops, Garland said that most gardeners should go with a mix of annuals and perennials.
“While investing in perennial plants can get a bit pricey, annuals can be way more expensive in the long-run if you’re purchasing new plants every year,” Garland said. “Now is a great time to start native plants from seed outdoors. Annuals can be very rewarding to grow from seed either indoors or sown directly into the garden when the soil warms.”
Plus, having a mix of perennial and annual plants in an ornamental garden will keep it aesthetically lush and beautiful.
“With ornamental crops one of the reasons people choose annual [plants is that] many of them have been bred to keep on flowering,” Goossen said. “Each perennial plant usually flowers for one specific time period and then there are less flowers, [though with] modern breeding, more and more perennials that will rebloom later in the year.”
Ultimately, though, both annuals and perennials — and everything in between — have their benefits. The most important thing for gardeners is to understand the characteristics of each of their precious plants and balance their garden accordingly.