Annual vs Biennial vs Perennial

Here in Canada, when deciding which flowers to grow, we often think in terms of whether or not a plant will survive the Winter. Plants are affected by seasonal changes (temperatures, hours of direct sunlight, etc.), but they also abide by their own cycles within those changing seasonal rhythms.

Understanding differing life cycles of flowering plants can deepen our plant relationships & help us to get more out of our gardens.   

Annuals - Quick Facts

• Annual flowers live out their reproductive cycles in just one growing season.
• Annuals reproduce using seeds.
• Self-seeding annuals create a “perennial illusion” by planting the next generation for you.
• Some plants that we grow as annuals are actually fast growing perennials from warmer climates; they just can’t survive our cold Winters.
• Annuals are lovely when planted in the veggie garden! Edible annuals like Borage & Calendula make great additions to salads & they welcome endless beneficial insects. Other annuals, like Marigolds, deter pests!

Starting annuals as transplants in early Spring helps extend their flowering season. Because they are so short lived, annuals tend to be a bit frantic about reproducing & have the ability to flower almost continuously! Removing dying blossoms, thereby preventing seed production, encourages a prolonged bloom. Pair this with even watering & nutrition (compost tea or seaweed emulsion work great!), & you can keep most annual flowers blooming all Summer & into the Fall.

Biennials - Quick Facts

• Biennial flowers require two years to complete their life cycle.
• Biennials reproduce using seeds .
• Self-seeding biennials offer a perennial effect, as they drop their seeds in place.
• Year #1 - A robust root system is established, as well as low-to-the-ground leaves.
• Year #2 - Taller stems develop, which give life to flowers & eventually seed pods.
• Having completed their two season reproductive cycle, biennial plants die away.
• Many common vegetables are biennial, including cabbage, beets, onions & carrots.

Biennial cycles are signaled by changes in the environment; sometimes by drought but generally it's cold-induced dormancy (ie. Winter) that does the trick. 

There are some beautiful but tender Biennials, like Artichokes, that struggle to survive Canadian Winters. Luckily, many tender biennials can be encouraged to flower in just one short season by exposing them to an artificial cold period early in the season. This is called vernalization; a simulated Spring.

As with annuals, deadheading can help to prolong blooming. That being said, it can be incredibly rewarding to collect seeds from your own biennial flowers! Hollyhocks, Foxglove & Mullein are a few of our personal favourites. 

Perennials - Quick Facts 

• Perennial plants live for three years or more.
• Perennials are only perennials when grown within their specified Winter hardiness zone!
• While perennials can reproduce by seed, many also reproduce via roots, corms & rhizomes .
• Perennial flowers are often “seasonal bloomers” & their bloom-times often correlate with the arrival of their preferred pollinators.
• Herbaceous Perennials - Foliage & stems die back to the ground in Autumn & regrow year after year.
• Woody Perennials - Branches remain from year to year & compliment the Winter garden. Selective pruning can improve flowering & fruiting in years to come.

Perennial life spans are variable. Short-lived perennials, like Lupins & Delphinium only flower reliably for about 5 years. Luckily, Lupins self-seed readily & flowers like delphinium or lilies are easily divided. Thankfully, easy propagation is the case for most short-lived perennials.

Longer lived perennials can go for decades, becoming precious family heirlooms. Flowering may slow down, but can be encouraged through informed pruning. Many Flowering Tree species, as well as perennial Flowering Vines can live for hundreds of years!