In an ideal garden, I suppose individual plants would bloom all season long, providing continuous color. Here in Colorado, season-long bloom is rather uncommon, other than with annuals.
As for perennials, bulbs and shrubs, a long bloomer along the Front Range could be defined as one that produces flowers non-stop for four to six months. Fortunately, there are a few stalwarts out there, including those mentioned below.
- Catmint (Nepeta). My favorite catmint is little Trudy—a sterile, drought-tolerant cultivar that grows into a compact mound of lavender fluffiness lasting from May to October. If Trudy begins to poop out in the summer heat, simply shear her back, and she’ll be fluffed out again in a week or two. This perennial grows about a foot high and 1.5 feet wide.
- Prairie winecups (Callirhoe involucrata). Winecups generates vines up to 2.5 feet long that are loaded with burgundy blooms about an inch in diameter. This stalwart perennial grows about six inches tall and can handle the hottest, driest conditions in your landscape. Like little Trudy, winecups blooms from May to October.
- Rozanne cranesbill (Geranium ‘Gerwat’ Rozanne). If you love lush, lavender blooms, Rozanne is for you. This hardy perennial grows in full sun to part shade and boasts blossoms about an inch in diameter. The plant itself grows about 1.5 feet high and 2 to 2.5 feet wide. Rozanne isn’t as drought-tolerant as catmint and winecups, so water it once or twice a week in hot weather. She’ll give you color from June to September.
- Coreopsis and Blanket flower (Galliardia). These two beauties will bloom from June to September. I’ve stopped growing them, however, because they require such frequent deadheading.
- Stella de Oro daylily (Hemerocallis ‘Stella de Oro’). Unlike most other daylilies, Stella d’Oro blooms from May to August, displaying soft yellow blossoms. Stella grows about 1 foot high and eventually will spread to the point that you’ll need to divide her to make new Stellas.
- Roses. There are quite a few roses that will bloom from June to September. One drought-tolerant favorite is Linda Campbell, which grows about 5 feet high and wide, with deep red flowers. Long-blooming groundcover roses include sea foam, white meidiland, fire meidiland, scarlet meidiland, and magic meidiland. When looking for long-blooming roses, check for “good repeat” or “continuous repeat” in the plant descriptions.