In the searing heat of late summer, perennial gardens often lose their charm. The early summer flush of bloom is over for many of the traditional garden favorites. Yet, in a garden planted for the "dog days," August may well highlight the most vibrant floral display of the summer.

Moderately watered gardens glow with asters in shades of pink, purple, and white. Garden phlox bloom in semi-shade or sun exposures, lovely footed by plumbago (Cerastostigma plumbaginodes) with brilliant blue blossoms and leaves turning red at the first hint of fall. Echinacea or coneflower flourish in watered and dry gardens, the brilliant pink with orange cones most common though a beautiful white form, "White Swan," eliminates any potential color clashes. Chrysanthemums of intense shades and various sizes are beginning to flower. If one is a hollyhock fancier, Althea rugosa, a giant pale yellow, is a stunning choice. Various bellflowers continue to open their nodding flower heads and obedient plant, a tall spreading clump, sends up spikes of sparkling white or pink.

Though traditional gardens can be colorful in August, it is in the hot dry garden that the "showstoppers" reign. Look to the native plants and palette of the Colorado landscape when choosing plants for late summer bloom. Liatrus shoots two to three feet tall in fuzzy spikes of purple or white. Sunny daisy like flowers, cover masses of black eyed Susan. "Goldsturm" is a good choice. The waving plumes of goldenrod flourish in sun or semi-shade. Gaillardia, blanket flower, blooms in the hottest driest exposures. Russian sage, a striking four or five foot light purple cloud, is a beautiful backdrop for the yellows dominating this season. For the more adventurous gardener, the Agastache or hyssop family stars many late summer bloomers; "Sunset," whose wispy spikes smell of licorice, is the color of a Colorado sunset. More suited to a well-watered garden is "Bubblegum," spikes of pink scented like gooey pink bubblegum.

Though the beautiful gardens of early summer have bloomed and retreated for another season, plan and plant for the heat of August. Visit a favorite garden center, ask acquaintances about the flowers blooming in their gardens, search for favorite "dog day dandies" and enjoy the vibrant late summer show.

Q: How late should I continue to remove spent blooms from my roses?

A: It is fine to remove spent blooms from your roses through the month of August. Remember to cut the old bloom stems back to a five-leaflet leaf or until the cane is about the size of a pencil. Beginning in September, cut any spent blooms just below the bloom so as not to stimulate new growth which could be injured by frost.

Q: How late in the summer should I fertilize my roses?

A: You should fertilize your roses during or after the second bloom, usually around the middle of July. Remember to apply the last nitrogen fertilizer about two months before the first killing frost in your area to avoid damaging any new growth.

Q: How should I prepare my roses for fall and winter months?

A: Begin to reduce watering in early September to allow the plants to begin their hardening off process in preparation for dormancy. Be sure to water the bed thoroughly before the first freeze to lessen the damage to the roots. When the temperatures get to the low 20s for several nights, cover the graft and lower part of the canes with s few shovels of loose soil or mulch to protect the plant from extreme changes in temperatures. It is also wise to cut the old stalks to about two feet in height to minimize damage from wind and snow.

Musk thistle (Carduus nutans), plumeless thistle (Carduus acanthoides) and Scotch thistle (Onopordum acanthium) are biennials and reproduce by seed. Keep these plants from flowering and producing seed and you should be able to eliminate them.

Fertilize, water and deadhead the faded annual flowers to keep them blooming until frost. You can also keep perennials blooming a little longer by deadheading spent blossoms.

Treat all members of the cabbage family (broccoli, cauliflower and cabbage with Bacillus thuringiensis (Bt) to kill cabbage worms. Use Bt "San Juan" strain for the larvae of the Colorado potato beetle. Full grown Colorado potato beetles can be hand picked from the potato foliage.

Harvest and dry "everlasting" flowers like yarrow, baby's breath, lavender, statice, strawflower, globe amaranth, sea holly and cockscomb. Pick the flowers before they are fully open, strip off the foliage, gather small bunches with rubber bands and hang upside down in a cool, dark place.

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:  August 23, 2004