Bloom time in most Rogue Valley perennial gardens runs from late May through early July – a glorious but short 5 or 6 weeks. By now, most perennial gardens are past their prime and look pretty dull for the rest of the season.
Fortunately, there are many perennials that bloom in late summer, including coneflower, asters, mums, Russian sage, sedum, rudbeckia, and phlox. I do believe, however, that annuals are the real key to summer-long color.
Unlike many perennials, most annuals thrive in summer’s heat and once they get started, will keep blooming right into early fall. With a little planning you can create companion plant partnerships that will keep your flower gardens looking terrific for a full 5 or 6 months, as well as providing forage for hummers, butterflies, and a host of other pollinators and beneficial insects.
Here are some things to consider before you rush out and purchase a ton of bloomers:
Choose the right style of annuals.
You don’t want plants that are too large or too bold in flower or foliage. The best companions are vase-shaped, old-fashioned flowers. The types of annuals that work best are those that weave among the foliage of your perennials. Good examples include verbena, nicotiana, salvia, and heliotrope.
Choose heat-tolerant annuals.
Unless your perennial border is in the shade, you’ll want to select sun-loving, warm-weather plants such as alyssum, morning glory, nicotiana, salvia, verbena and petunias.
Don’t neglect the heat lovers.
There are many fabulous heat-loving plants that can be used as annuals. Though many of these are quite large and possibly too bold to blend into the average perennial border, you may want to find space for them. Good candidates include canna, elephant ear, ginger lily, and Mexican sage.
In my garden, most of the annuals go right in with the perennial borders in the spring. Others get planted in the cutting garden and get moved over as needed to fill those inevitable holes that occur as the season progresses. It’s best to choose a rainy day or a full moon evening to move these plants, which may already be in flower, but if you soak them well ahead, and keep the root ball intact, they should survive the move just fine.
To lift your garden out of the late-summertime rut, consider some of these alternatives. You may be able to find them in containers at your local garden center.
Matricaria: This bloomer brings with it a refreshing blast of white. You’ll probably need to grow it yourself from seed, since I’ve never personally never found it offered in nurseries.
Mums: Some varieties will overwinter here in zone 4, but I usually treat them as annuals. Plant a couple fist-sized clumps in the spring. By fall each plant will give you dozens of long-lasting blooms. For good late season color, keep your mum plants pinched back until early July.
Coleus: There are hundreds of incredible colors of coleus to choose from. Pinch them back to keep them bushy and remove the flower heads as they appear.
Anise Hyssop: I love this plant for so many reasons, and I’ve grown it for so many years that it now self-sows in my containers. It’s not exceptionally showy, but has good foliage and form, with fluffy purple flowers in August and September.
Salvia horminium: This is a great plant with purple, pink or white elements to each flower. Like a poinsettia, it’s the top leaves that provide the show, not the flowers. Salvia horminium looks good right through late fall.
Impatiens: The pink ones. No wait, the orange ones. No…the pink ones. Impatiens bloom until frost, and the dependable splashes of color really help pull your borders together.
Bishop’s Weed: This plant looks like an airier version of Queen Anne’s lace. Sow it successively from June through July since the plants fade after a couple weeks of blooms. And, of course, the pollinators LOVE Bishop’s Weed.
Sanvitalia procumbens: This low, spreading plant looks like a miniature black-eyed Susan. It loves the heat, and works well in rock gardens or at the front of a sunny border.
Salvia farinacea: The purple ‘Victoria’ has rich green foliage and spiky blue flowers. Its form is a bit stiffer than most good perennial companions, but it makes a great mid-border filler, and pollinators love it.
Bringing some new things into the garden can make this late-summer/early-autumn time a glorious and enjoyable time in your garden. Be sure to keep track of what works for you and brings those memorable flashes of color. You’ll want to recreate the brilliance of this summer and autumn for many years to come.