Answer: Perennials typically bloom for a period of about 3 weeks. If you want color throughout the year, you might try planting two of three different varieties so you can enjoy each when they come into bloom. Here are a few favorites:
Achillea is a long blooming plant for full hot sun
Agastache ?Blue Fortune? or licorice plant is one of the better longer blooming Agastache.
Anthemis tinctoria is a long blooming daisy that will self sow with abandon.
Asters. There are a few fall blooming asters such as ?Monch? and ?Wonder of Staffa? that are extremely long blooming. Check out the newer varieties.
Campanula a decent long bloomer three years out of four.
Centaurea montana was a reliable plant for me but self seeded everywhere.
Centranthus is easy and a little known but decent blooming plant.
Chrysanthemum. Everybody knows Shasta daisies and Fall mums. Deadhead the Shasta daisies for longer blooming.
Coreopsis. All bloom for extended times but the lanceolata and grandiflora types benefit from deadheading to get repeat blooms. Deadheading is not necessary with verticillata and rosea hybrids to make them into long blooming perennials.
Corydalis lutea is my favourite long blooming perennial and simply the longest blooming plant in my garden.
Dianthus can be very long blooming perennials if you pick new hybrids. Dianthus gratianopolitanus and D. deltoides are two of the best.
Dicentra Formosa and D. exemia hybrids are long lived for shade. Short bleeding hearts are superb while the taller ones are short bloomers. ?Luxuriant? has been my shade garden stalwart.
Echinacea are the current darlings of the plant breeding world and it is true the blooms last a long time and each individual flower lasts a long time. Good for mid summer blooms and so far they all seem to be about the same length of time in my garden.
Gaillardia are long bloomers but tend to be short lived. Will self sow but what a bloom they give.
Gaura plants are tremendous long blooming perennials and with its airy butterfly like flowers, it is a garden ornament worthy of the best designers. Grow it.
Geranium ?Rozanne? is a season-ling blooming geranium and the others are so-so long season bloomers. Watch for more repeat bloomers such as ?Jolly Bee? with its huge two-inch blue flowers. Both are stunning long blooming perennials in my garden (I like geraniums.)
Hemerocallis or daylilies ?Stella D? Oro? is the classic but look for ?repeat bloomers? at your favourite garden shop. See note in the introduction.
Heucherella ? this cross between Heuchera and Tiarella has produced some very long blooming plants with dainty flowers. Not for heavy competition in the main flower border against phlox and daylily but lovely in containers or small dainty gardens.
Hibiscus moscheutos or perennial hibiscus is a very long blooming fall plant and the modern hybrids are simply stunning. I have three and I lust for more.
Kalimeris pinnatitida "Hortensis" or Japanese Asters produce a profusion of small flowers or a very long period of time.
Kniphofia can be long bloomers if you can grow them. The used to be very short green plants in my old garden. Haven?t gotten around to killing any in the new one yet.
Lavender is a classic long blooming plant for growing anywhere in the full sun.
Liatris, is Gayfeather or Blazing Star and is a good long bloomer and unusual flower heads.
Linum perenne or perennial flax is disappearing from garden centres because the larger nurseries have a hard time growing it. It produces literally hundreds of blue flowers every day almost all summer from early July onwards. Grow it yourself from seed ? direct sow it in the garden ? it is easy.
Malva sylvestris or ornamental mallow blooms for a long time but is very weedy.
Nepeta or Ornamental Catnip is a good plant if you get the newer hybrids. The old species plants are not as long blooming.
Perovskia or Russian Sage gives a good blue mist to the garden in late summer and early fall and is a good plant in full sun gardens with great drainage.
Phlox paniculata or garden phlox. No list would be complete without this classic backbone plant. Pick modern mildew resistant hybrids so the plant will keep its foliage on until August.
Rudbeckia or black eyed Susan is a good long bloomer. ?Goldsturm? is the classic standard and well worth growing. Pooh-poohed currently by the gardening ?elite?, because it is over-used and ?boring?. It is overused because it is rock hardy and long blooming. Go figure.
Sedums are very long blooming perennials in the fall garden and I can?t imagine a fall garden without them. Great new variegated varieties mean you don?t have to depend on flowers but the leaves give you season-long appeal. Again, newer varieties have different colored foliages as well as good flower times.
Stokesia or Stoke?s Aster is a good bloomer particularly if you deadhead it.
Best wishes with your garden!
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