Gardening in Larimer County

Many gardeners are on a quest for the perfect plant: one that doesn’t need to be planted every year, but one that blooms all summer long.  We’re seen in the perennial section of nurseries scrutinizing the descriptive tags on plants, skeptically reading the phrase “blooms May until frost.”

Those of us wise to the ways of perennial plants know that descriptions of bloom time are often exaggerated.  “Blooms all summer” can mean that the plant sends up sporadic flowers throughout the hot season without ever rewarding us with one spectacular flush of bloom.  Or it can mean that the plant is a prolific bloomer in its native climate, a climate that is not our own.  Sometimes the phrase is merely shorthand for “blooms in summer (no one really knows when)”.  However, there are a few precious perennial plants that really do live up to their advertising and flower for months on end.

 “Pink Mist” and “Butterfly Blue” pincushion flowers (Scabiosa columbaria) are two of the most generous perennials in the flower garden.  With moderate water and at least half a day of sunlight, these fifteen-inch tall plants send up countless mauve and lavender flowers from May until frost.  As a bonus, the flowers are borne on long springy stems, which make them an ideal cut flower.  To keep these and other long-blooming plants looking their best, deadheading is essential.

For gardeners who prefer a brighter palette, blanket flower or (Gaillardia x grandiflora) fits the bill. The two-inch red and yellow flowers add a spicy touch of salsa to the garden and thrive in sunny dry spots.  Blanket flower combines well with yarrow, another drought-tolerant, long-blooming perennial.

While some yarrows can be pesky self-seeders, the yellow flowering varieties Moonshine and its taller cousin Coronation Gold are delightful, well-behaved plants. Moonshine’s flat lemon yellow flowers are a striking contrast to its cool gray foliage.  Coronation Gold is a warmer yellow color.  Both varieties make excellent dried flowers.

Two repeat-blooming daylilies, Stella d’Oro and Happy Returns can also brighten a garden.  These daylilies only rise about a foot from the ground and have attractive grassy foliage.  Stella d’Oro’s flowers are a familiar school bus yellow, but the canary yellow blooms of Happy Returns are not so well known.  Both daylilies offer cheerful flushes of flowers throughout the summer.

Another long-flowering perennial that blooms in flushes is May Night Salvia or (Salvia nemorosa “Mainacht”).  In May and June, it offers a stunning display of 2 foot tall midnight purple flower-spikes.  Then, if the plant is cut back, it begins the show all over again.  May Night Salvia adds a touch of drama to any garden.

Whirling butterflies (Gaura lindheimeri) features wispy wands of butterfly-like flowers from late June until late summer.  The white or hot pink flowers are arranged on delicate wine-red stems that reach about eighteen inches in length.  Unfortunately, this beautiful plant is known to expend so much energy in blooming that it tends not to have a very long life.

Pink evening primrose (Oenothera speciosa) looks fantastic with whirling butterflies.  It has delicate pale pink flowers atop eight-inch stems.  It can bloom for close to three months. Other sun-loving plants with long bloom times include catmint, Max Frei soapwort, prunella, Starburst ice plant, Goldsturm Rudbeckia, winecups, sidalcea, and some varieties of coreopsis.

Few shade plants offer sustained bloom.  Fringe-leafed bleeding heart or (Dicentra exima) can produce romantic, heart-shaped flowers from May to frost if given rich, moist soil.  (Corydalis lutea) has lacy foliage similar to (Dicentra exima) and has also been known to produce small yellow flowers throughout the growing season.  However, successful shade gardeners look to beautify their gardens with plants that can offer more than just flowers.

In fact, looking for plants with attractive foliage and interesting structure is a good rule for all gardeners.  Perhaps this is the ultimate lesson of the perennial garden: long bloom is nice, but it is not everything.  Perennials can be beautiful for their foliage color, their texture, and their structure.  Beautiful flowers are just a bonus.

Q: This year the leaves on my hollyhocks look awful.  What can I do?

A: If the leaves are covered with powdery orange spots, your hollyhocks probably have rust, a type of fungus that often afflicts hollyhocks.  If you discover the problem early in the season, you can try to remedy the situation.  Remove effected leaves, apply a fungicide and avoid overhead watering.  Next year, try planting your hollyhocks in a different spot, away from soil that may contain the rust spores, and always water your hollyhocks at the base of the plant.  Also, you might want to try planting the rust-resistant variety of hollyhock, the pale yellow Alcea rugosa.

Q: Can you recommend a vine that will cover a chain link fence fast?

A: If the fence is in a shady area, you might try Dutchman’s pipe.  It is a vine with large, heart-shaped leaves that will lay completely flat against a fence, and it has an inconspicuous pipe-shaped flower.  If the fence is in sun, you could try silver lace vine, grapes, Virginia creeper, or sweet autumn clematis.  Silver lace vine is a drought-tolerant vine that features lovely sprays of small white flowers in summer.  Virginia creeper also tolerates drought.  It has large green leaves that turn a vibrant scarlet in the fall.  Sweet autumn clematis is a fall-blooming clematis.  Its hundreds of white flowers smell like almonds.

Q: My bee balm is covered with white flecks.  What are they, and how do I get rid of them?

A: Your bee balm (Monarda didyma) probably has powdery mildew.  Powdery mildew is a fungus that produces spots that look like talcum powder on the newer foliage of plants.  A variety of plants get powdery mildew (roses, asters, bee balm, and cucumbers) but many different species of the fungus are responsible for the disease on different plants.  Generally, powdery mildew affects plants that are in a bit of shade during the day and in areas of poor air circulation.  Fortunately, powdery mildew is usually most in evidence after bee balm has bloomed.  Once powdery mildew has developed on bee balm, it is best to cut the diseased foliage back to the leaves at the base of the plant.  Dispose of the leaves, and do not compost them.   Next spring, you might want to consider moving your plant to an airier, sunnier location and thinning out some stalks of the plant.  You might also investigate varieties of bee balm that are more mildew resistant like Jacob Cline (red), Marshall’s Delight (pink), or Violet Queen.

Q: This year my perennial geranium had a nice mounded form at the beginning of the summer but now is messy looking and falling open.  Is it okay if I cut it back?

A: Many of the larger perennial geraniums (geraniums that do not need to be replanted every year) tend to flop around once they have flowered.  It is safe to cut these plants back.  If possible leave some of the leaves, but for some geraniums, like Johnson’s Blue, it is all right to cut the plant right down to the ground.  It will rebound and start producing new shoots very quickly.

Watch for aphids daily. Check buds and undersides of leaves. Jet them off with a spray of water. If that isn’t succesful, use an insecticidal soap in the cool part of day.

Keep flowerbeds weeded. Do this when soil is moist and then immediately follow with 2-3 inches of mulch. This will help keep moisture in and weeds out.
Take a quick snapshot of your beds now; then you’ll know exactly where to focus your efforts when winter planning time is here.

For full, bushy plants in autumn, complete final pinching of fall-blooming chrysanthemums.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

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This page updated:  March 13, 2003