Erica Browne Grivas
When we start gardening, most of us are drawn to annuals, both ornamental flowers and edible crops, like moths to a flame. Like a flame, annuals shine with a dazzling light, burning brightly. The flame dances, gives heartening warmth, and lasts for weeks, even months. Yet frost snuffs out that flame forever. For a repeat performance, you’ll have to buy starts or grow from seed next year. Perennials are a slower burn, but if chosen with care, return each year. Instead of returning for months or weeks, it’s for years or decades to come. So, for many, perennials are the winner for value. But is that true for you?
Who’s Who and What’s What
First, let’s get through the name thing. It’s confusing. We don’t use the word “perennially” as much as “annually,” so when people hear “annual,” they think “Ah! It comes back every year,” like Bumbershoot. In the plant world, annuals must be started from seed anew each year. They complete their life cycle and set seed within a growing season. Perennial plant roots over-winter in a dormant state underground to re-grow the next year. So, rather than blooming their heads off to reproduce, perennials reserve some energy to save for spring. Their bloom season is typically shorter, but they don’t need replacing as often.
Benefits of Annuals
Productivity –
While it’s foolish to generalize when it comes to the vast and intricate world of plantdom, in general, the big appeal of annuals is in production. Because they have shorter time on the planet to reproduce, they make up for it by creating masses of seeds through flowers or fruit. As their willing accomplices in spreading this seed, we harvest armfuls of dahlias, tomatoes and zinnias.
Long season –
When you want reliable, set-and-forget color (with regular care), annuals get the nod, especially for the main growing seasons of spring through summer. It would be possible, in a sunny container, to have violas from fall through early spring followed by geraniums or bedding daffodils with very few gaps in color. Exciting? Perhaps not. But easy? Definitely.
Flowering annuals are great adds for “power spots” like your front door, window box, by a gate or driveway or patio. Annual food crops have delicious and nutritious benefits that speak for themselves.
You’ll want to be aware of the plant’s frost tolerance to know when you’ll wake up to a pile of black mush outside.
Lastly, a caveat to the “must-replace” rule for annuals: annuals that “self-sow” can replicate themselves where happy (requires loose, empty soil of their preferred type). They may not return in the same quantity or place you intended, however. I have planted Cerinthe major starts in my well-drained sandy hillside by my front door in more than one summer. Where does sow itself? In the cracks in my driveway.
Downsides of Annuals
In addition to the cost of replacement, annuals are – here’s another generalization – as a rule, more fussy than well-sited perennials. They are growing so fast; they need more support from the gardener. We are talking especially about plants we tend to buy in six-packs: peas, and basil, alyssum and petunias. Very drought-tolerant annuals like geraniums, tubers like dahlias (which are semi-perennial here), and street-tough weeds like crabgrass are a different story.
The plants are usually seedlings, barely out of seed starting mix, and need to adjust to your new soil and climate conditions. We usually expect trees and shrubs to need extra watering for up to three years to establish their roots; annuals only get a few months. They’ll need watering more often, especially in containers, and many pests find their succulent new foliage delectable.
They may need extra fertilizer support, again especially in containers, because you’re asking the peas to grow four feet in a season, for instance.
Benefits of perennials
Perennials have grit and staying power.
If you choose according to “right plant, right place” principles, your perennial should love the spot you’ve picked, according to your existing soil and real-world weather conditions. Most nurseries sell perennials well-suited to your region and zone, (Seattle is Zone 9a now), but the best strategy is doing your homework about your microclimate and your intended plant.
They will need lower maintenance in the long term than annuals. Yes, they will need supplemental water those first two or three summers, but you’ll be rewarded with strong healthy plants that will return for years. Some plants inherently last longer than others. Some wallflowers like Erysimum ‘Bowle’s Mauve’ are short-lived perennials that bloom almost like an annual, but may need replacing in a few years. Daylilies, Hosta, iris, oriental poppy, baptisia, and peony are some that can last decades. As a bonus, once established, their deep roots help them fend off weather extremes more than annuals.
Beyond a top-dressing of compost in the fall or early spring, they shouldn’t need additional fertilizer. (Because you picked perennials that like the pH and drainage in your soil, remember?)
As such, for year-to-year cost, perennials are the winning budget choice.
Downsides of Perennials
The upfront cost per plant is usually more than annuals. Exception: grafted one-gallon tomato plant, $19.99. But amortized per year of enjoyment, the cost of perennials goes down.
You do need to baby them with watering those first years getting established in your garden, and some mulch is always nice. After that period, your cost in time and water should shrink significantly, particularly with drought-adapted perennials.
Lastly, because perennials have a shorter bloom period compared to annuals, if you want consistent color, you need to choreograph a color symphony with multiple varieties of perennials. You might have geum, allium and poppies followed by yarrow, salvia, and echinacea, and then asters and chrysanthemums. My father fantasized about rolling shelves that brought new bloomers into view as needed for this purpose. Failing that, you have to plan your bloom sequence like a normal gardener.
What’s the answer?
That depends on you and your garden. If short-term, consistent color or a bountiful crop of veggies or buckets of zinnias is your dream, annuals may be your priority. If you plan to garden for several years at your property, perennials deliver more environmental benefits and value, needing fewer inputs long-term.
You can find annuals and perennials that offer great pollinator benefit – seek out native or regionally native annuals or perennials especially those in the mint and aster families.
Of course, if you know me at all by now, you know I don’t choose. My garden is bursting with a diverse crew of annuals, biennials, and perennials, not to mention shrubs and trees. Some of my highest value, meaning the bloomingest, lowest-effort perennials are yarrow (Achillea), Geranium ‘Rozanne,’ and Agastache ‘Blue Boa.’ I love self-seeding calendula and California poppies. But I hold space (and time and water and fertilizer and potting mix) for my dahlias and tomatoes.