Alan is the Director of Horticulture at Powell Gardens and author of The Gardener’s Butterfly Book. He holds a bachelor’s degree and master’s degree in landscape architecture from Iowa State University and Louisiana State University, respectively, specializes in garden design and maintenance, and has supervised and designed dozens of landscaping projects. A member of the American Public Gardens Association, Alan plays a key role in Powell Gardens, one of the largest botanical gardens in Missouri. The garden boasts world-class architecture and more than 17,000 accessions of plant displays that capture the essence of the American Midwest.

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Max Bloom
by Alan Branhagen    

Continuous bloom is always a hot topic among gardeners. Here are several ideas and techniques that can help you extend the bloom time of your beloved plants.

Most gardeners want annuals and perennials with flower power — those with abundant flowers that last as long as possible. We also want some of the classic plants we are familiar with and each has its bloom limitations. Are there things a gardener can do to increase and extend the bloom time of popular plants? You bet!


Deadheading (removing the spent flowers) is a classic way to keep many plants in bloom, but who has time for that? It also doesn’t work for some plants programmed to bloom at a specific time, often based on a day’s length. Some basic points to start with include proper watering and fertilization. More is NOT better. Too much water and too much fertilizer often encourage plants to grow all sorts of foliage at the expense of flowering. Water only as needed, the same goes for applying fertilizer.


My number one tip for improved bloom over a longer period of time is to choose the proper varieties. There are cultivars of many plants that have been selected for this trait. Formerly “one-shot” flowers like tall bearded iris and daylilies now have readily available selections that repeat bloom! I’ll admit I’m amazed at some of the plant selection and hybridization breakthroughs that have changed my perceptions of some plants from seasonal treats to great garden workhorses.


Part two of the proper plant selection scenario (in regards to perennials) is that there are usually early, mid and late season species or varieties of a particular perennial. That means a certain group of cultivars blooms early for that particular plant while other cultivars naturally bloom later. Planting groupings of related cultivars of early, mid and late sequence of bloom can give the impression of something in bloom for an extended season. It’s often best to site the later blooming varieties in the foreground so that you are looking through buds to the open blooms of the earlier varieties. Your eye is always drawn to the plants in bloom.


Shearing or cutting back a plant is much easier than clipping individual spent flowers and there are several flowers for which this makes all the difference in the world. Beware, it does not work as a universal rule and might be the ruination of some plants. Actually, shearing part of a clump of a plant works on some varieties — just make sure you shear the part facing the front! The sheared portion often blooms a bit later as it takes the plant more time to regrow flower buds. Some plants like asters and chrysanthemums that bloom based on day length won’t be fooled by this and will either still bloom at the same time or the sheared part won’t bloom if it was trimmed too late in the season.



Here are some tips that will allow you to extend 15 garden flower favorites’ bloom season.


1 Sweet Alyssum (Lobularia maritima)

This classic cool-season annual is admired for its low format and intensely honey fragrant flowers. It does well in spring but fades with the summer heat. You can shear it back in late summer for a repeat in the fall, but we now have a heat-tolerant cultivar ‘Snow Princess’ that will carry on right through the heat. 


2 Bee balms and Bergamots (Monarda spp.)

This group of related perennials and their hybrids mainly blooms in midsummer. It is a classic perennial for shearing part of the clump back in late spring (early June) so that the sheared stems are forced to re-grow and set new flower buds. This is a great way to extend the bloom—the un-sheared portion will bloom first while the sheared portion will bloom later. Monarda bradburiana blooms a month earlier than the others and its hybrid ‘Prairie Gypsy’ also blooms ahead of most, so if you like monarda plant those for a longer season.


3 Perennial Black-Eyed Susans (Rudbeckia fulgida)

A selection of different cultivars and varieties of this classic perennial really extends its summer cheeriness. ‘Early Bird Gold’ blooms first, followed by ‘Viette’s Little Suzy’, 1999 Perennial Plant of the Year ‘Goldsturm’ and then the latest blooming is var. fulgida, often lasting two to three weeks longer. With this mix you can have these in bloom for at least three full months.


4 Blazingstars (Liatris spp.)

Blazingstars are classics with wands of purplish (or white) flowers but in slightly different arrangements on a score of different species. They all bloom from the top down and at slightly different times. Plant a variety of species and you can have blazingstars blooming from midsummer through fall. Cylinder-like Liatris cylindracea is shortest and first to bloom followed by spiked blazingstar (L. spicata, and ‘Kobold’ is a common cultivar), then prairie blazingstar (L. pycnostachya), and then meadow and Eastern blazingstars (L. ligulistylis and L. scariosa), followed in autumn by the rough blazingstar (L. aspera).


5 Daffodils (Narcissus spp.)

Daffodils are the showiest spring flowers held dear to gardeners for their deer immunity. The flowers can last a long time in cool weather or go quickly in spring heat. Plant early, mid and late season varieties together to ensure a long season of bloom. If any one group goes quick you have the others to fall back on. An example with “trumpet” daffodils is ‘Rijnveld’s Early Sensation’ (very early), ‘Goldfinger’ (mid) and ‘Pay Day’ (late).


6 Catmint (Nepeta spp.)

Plant selection and shearing are the way to extend the cool blue flowers of this tough, long-lived perennial. ‘Walker’s Low’ is the way to go, as it can bloom from late April into November! As it starts to wane and splay, give it a midsummer shearing for renewed bloom and vigor through the season.


7 Threadleaf Coreopsis (Coreopsis verticillata)

This perennial has another star: ‘Moonbeam’ 1992’s Perennial Plant of the Year. Give it a midsummer shear like catmint and you are good to go with flowers from June into October. Other cultivars like ‘Zagreb’ with a richer yellow flower will work like monarda and can have extended bloom by shearing a portion of the plant.


8 Daylilies (Hemerocallis spp.)

This indestructible perennial with stunningly large midsummer flowers of warm colors really speaks to our brightly lit summers. New selections have higher bud counts and have been bred to rebloom. ‘Happy Returns’ daylily is aptly named and the epitome of these traits; here are some others: ‘Bama Music’, ‘Bertie Ferris’, ‘Black-Eyed Susan’, ‘Ice Carnival’, ‘Little Grapette’, ‘Pardon Me’, ‘Pastures of Pleasure’, ‘Spanish Glow’ and ‘Spiritual Corridor’.


9 Tall Bearded Iris (Iris x conglomerata)

These extraordinarily showy and colorful “king of the rainbow” flowers were once a one-shot floral show. New hybrids have brought the reblooming nature to them so you can enjoy a repeat of their spectacular and fragrant flowers if you select the proper cultivars. Aptly named ‘Immortality’ got my attention, and others include ‘Autumn Circus’, ‘Betsey Boo’, ‘Clarence’, ‘Feed Back’, ‘Harvest of Memories’, ‘Jewel Baby’ and ‘Mariposa Skies’.


10 Peonies (Paeonia spp.)

Peonies embody a springtime classic of magnificent and fragrant bloom. No, you can’t cut them back, nor shear a portion of the plant to get more peony blooms. Here again if you love this plant then make sure your border contains early cultivars (‘Buckeye Belle’ and ‘Coral Scout’), midseason varieties (‘Garden Lace’ and ‘Pillow Talk’) and lateseason bloomers (‘Garden Treasure’ and ‘Magic Moonbeam’) to extend the season.


11 White Lilies (Lilium spp.)

White lilies are the stars of the evening and moon gardens with their glowing white, fragrant flowers meant to allure nighttime pollinators. Different species and cultivar types bloom as in blazingstars—in a long sequence from before summer’s solstice until the autumnal equinox. Plant hardy Easter lilies (Lilium longiflorum ‘White Elegance’ is zone 5 hardy) for the first to bloom in June; follow with regal lily (L. regale). Next are white Oriental hybrids like ‘Casa Blanca’ or ‘Siberia’ with L. speciosum ‘Album’ in late summer and the Formosa lily (L. formosanum) as the finale.


12 Petunias (Petunia spp.)

In all but the coolest summer portions of our region, petunias can be a real challenge to keep blooming fully through the heat and humidity of summer. A good shearing after their spring fling may allow for a repeat performance in cooler fall weather, but the new Vista Series (‘Vista Bubblegum’, ‘Vista Fuchsia’, ‘Vista Silverberry’) Supertunias® have self-cleaning flowers that keep on blooming right through the summer in even our hottest zones.


13 Salvias (Salvia spp.)  Perennial and Annual

Salvias were all the rage a few years back and still deserve that status if you select the right varieties. The perennial meadow sage (Salvia nemerosa) is the best choice for a long season of bloom as varieties like ‘Blue Hill’, ‘Caradonna’ and ‘East Friesland’ can be sheared as flowers fade for a second and even third performance in our zones. For annual salvias, be sure and make selections that bloom without fall’s short days. ‘Wendy’s Wish’, ‘Indigo Spires’ and ‘Black and Blue’ are cultivars with great flowers that don’t wait until late fall when a tango with Jack Frost could ruin their show.


14 Garden Phlox (Phlox paniculata)

Garden phlox is an heirloom resurging in popularity with new breeding and selections resistant to powdery mildew. This mid-to late-summer bloomer can be cut back by half in late spring (early- or mid-June) to delay bloom—either on part of a clump as in monarda or in separate plants in the foreground of a grouping. Very similar species Phlox maculata and P. carolina naturally bloom earlier, so cultivars and hybrids of these (‘Minnie Pearl’, ‘Miss Lingard’, ‘Natascha’, ‘Omega’) extend the season.


15 Annual Vinca (Catharanthus roseus)

This marvelous warm-season annual has new breeding to make it a flower power even in our zones. The new Cora and Cora Cascade Series (‘Apricot’, ‘Burgundy’, ‘Deep Lavender’, ‘Lavender’, ‘Pink’, ‘Peach’, ‘Violet’, ‘White’, ‘Cherry-Lilac’, ‘Magenta’, ‘Peach Blush’ and ‘Polka Dot’ respectively) have abundant, self-cleaning blooms and resistance to the disease phytophthora, which destroys this plant in cool and wet spells in summer.



Photography Courtesy of:

1, 2, 3, 9, 10 Alan Branhagen

4 Midwest Groundcovers

5 Mary Louise Hagler

6-8 Bailey Nurseries

11 Lawrence Lu

12 Proven Winners

13, 15 All America Selections

14 Richard Hawke


Posted: 08/31/11   RSS | Print


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