CSU Trial Garden’s 2024 annual trial results: Best performing varieties
Media contact: Jennifer Dimas
(970) 988-4265
[email protected]
As the 2025 gardening season kicks off, many gardeners are asking the perennial question: what annuals should I plant this year? Fortunately, Colorado State University’s Annual Flower Trial Garden has some standout selections to inspire your summer garden.
Located on CSU’s Fort Collins campus, the three-acre garden serves as a hub for horticultural research and outreach. Each year, over 1,000 varieties of annual bedding plants are evaluated under the region’s challenging growing conditions. Dozens of expert judges assess each plant for traits like growth habit, vigor, and blooming performance, helping gardeners choose varieties that are more likely to thrive.
Winners from the 2024 evaluation are now available at area nurseries and garden centers for the 2025 home gardening season. For more detailed descriptions and photographs, visit the Flower Trial Garden website.
High resolution images of this year’s top performing annuals can be found here.
About the Trial Garden
CSU’s Flower Trial Garden draws in thousands of visitors annually and relies solely on student gardeners, volunteers and industry supporters and experts, who help provide detailed analysis of plant performance. Colorado State Extension Master Gardeners play a critical role in the garden’s maintenance and care, which results in valuable research utilized by industry and home gardeners alike. Due to the Rocky Mountain region’s unique growing conditions, such as high altitude, drying winds, intense solar radiation, and large fluctuations between day and night temperatures, regional growth analysis is critical.
The Trial Garden receives no direct state or public funding. It is funded primarily by fees from plant-breeding companies that submit entries to the trials. The garden also receives donations from foundations, industry associations, nurseries, plant producers and other green industry companies.
“Best Of” Annual Flower Winners from the 2024 CSU Trials
2024 “Best Of” Annual Flower Winners
Best of Show: City Lights™ Purple Dahlia
Selecta One
Dahlias are still quite popular with the visitors! A multi-year winner—it is that good! Bred for performance in heat, City Lights Purple lives up to expectations. This award-winning dahlia flowered through the summer, with rich, deep mulberry-purple flowers with a deep, nearly black center, accentuated by the dark green-black foliage that holds up well in the full sun all season. Bees and other pollinators also loved this plant.
Best New Variety (Grown in Ground): Karma Caroline Dahlia
Syngenta
A perfect dahlia for the garden. The clean peachy pink, ~3 to 4″ flowers have strong, sturdy stems on 3′ plants that are great as a cut flower! The colors are most intense in cooler temperatures, but even in the warm doldrums of the summer, the colors were still stunning. The dark green foliage provided a great backdrop to the abundance of flowers. A multi-purpose dahlia to consider for the landscape!
Best New Variety (Grown in Container): TerraScape ‘Queen’ Coleus
Kientzler North America
Talk about dramatic! And eye-catching! This vigorous coleus can make a statement in your garden. The deep red maroon leaves with a blaze reddish-pink center, and lime-green shark-toothed edges are eye-catching! And the colors hold up well in full sun! The plants are sturdy and strong and work well in containers!
Best Novelty: Dianthus Jolt™ Pink Magic
PanAmerican Seed
A great performing plant! A dianthus that flowered consistently and profusely through the summer in Colorado! The bright pink flowers with a magenta ring danced above the clean, dark green foliage. Heat–tolerant and one that you should consider for a jolt of color in the summer landscape!
“Best Of” Annual Flower Winners by Class
Ground Bed Winners
Coleus Ground Bed, Ruby Slipper, Ball Flora Plant
A coleus Dorothy would be proud of. This versatile coleus performed well in both sun and shade locations. In the full sun, it sports dark ruby red leaves with narrow, crisp green margins. The ruby red leaves sport wider green margins when grown in shadier conditions—sturdy, upright plants with no lodging.
Salvia, Lake Onega Improved, HilverdaFlorist
One of the Salgoon Series salvias, this beautiful dark blue-purple salvia has a long flowering period. It started flowering in the greenhouse and continued all through the summer, with great, sturdy stems and a uniform habit. It handles the heat well, and the bees LOVE it.
Verbena, EnduraScape™ Burgandy, Ball Flora Plant
This versatile verbena has a uniform, spreading habit and moderate vigor. Its attractive color is deep burgundy with flowers dotted with a white eye. Compared to others, it has consistent flowering and does not often have flushes of color. It also attracts some pollinators. This plant can handle high and low temperatures, down to 19°F!
Argyranthemum hybrid, Grandaisy® White Improved, Suntory
This intergeneric hybrid Argyranthemum showcased crisp, white flowers with a dark yellow-brown eye over vibrant green fern-like foliage. Flowering slowed slightly with the high heat, but as cooler temperatures returned, flowering picked up. Uniform plants.
Osteospermum, Zion™ Violet Feather, Selecta One
This African daisy was undoubtedly the best in the bunch. The deep, rich, silky purple flowers were produced all season, even with a couple of stretches of extreme heat. The flowers danced just above the medium green foliage on uniform plants. An osteospermum worthy of the garden or container!
Begonia, Tophat™ Rose Bicolor, Syngenta
The Tophat™ series is excellent, and picking just one favorite is hard. Rose Bicolor is the winner this year. It sports lovely crisp, glossy green foliage, with large rose and white bicolor flowers. No doubt the plants were floriferous all summer. Grow in full sun. It was noted that this was like a traditional bedding begonia on steroids!
Rudbeckia, SunBeckia® Marilyn, Bull Plant Genetics
It is hard to pick just one of the SunBeckias! Marilyn showed excellent uniformity and was floriferous, boasting a long-lasting canopy of flowers on well-branched plants. The large, bright sunshine yellow flowers develop a hint of cinnamon brown near the eye as they age, creating a dynamic flower display. A hit with pollinators!
Hybrid Impatiens, SunPatiens® Vigorous Purple, Sakata
These bold hybrid impatiens will help fill in a border planting. The large, intense purple flowers are contrasted against the deep green foliage, and will keep flowering, even as temperatures heat up. They are vigorous, with a strong branching habit. SunPatiens will certainly appreciate consistent moisture for maximum size and performance.
Impatiens walleriana, Beacon® Bright Red, PanAmerican Seed
Beacon® Bright Red is a versatile plant. It performed very well in full sun! And…does well in shade! The vigorous and brilliant red flower color holds up in the full sun—it doesn’t fade or melt out. Excellent for massing and filling in the landscape. It is one of several solid-performing selections in the Beacon® series, which is highly resistant to Impatiens downy mildew.
Catharanthus, Soiree® Double Orchid Improved, Suntory
One of several in the Soiree® series that performed well. This plant loves the heat! Uniform plants produced an abundance of silky, lavender colored flowers. The flowers hold up well in the heat, contrasted by the deep, dark green foliage.
Catharanthus (Seed Propagated), Titan-ium™ Punch, PanAmerican Seed
This seed Madagascar periwinkle certainly lives up to its name! It packs a punch of solid fruity deep pink to red punch color, all summer long! Nice, large flowers on highly branched plants. Like most Catharanthus, it loves the heat! This selection has been bred for high Phytophthora (root disease) resistance.
Lantana, PassionFruit, Ball Flora Plant
Aptly named—a floriferous lantana for the landscape. The multi-hued dallops of flowers that open a rich yellow, orange, maturing into a crisp, clean salmon pink. This spreading lantana is a great mingling plant for the landscape border or mixed container as the ‘filler’ component. It would also work well in hanging baskets. This is a heat loving, drought tolerant plant that attracts lots of pollinators—a great addition to the summer landscape.
Scaevola, Scala Purple Bird, Dümmen Orange
This fan-flower was a fan-favorite in the trials! It was among the top selections for the public and the horticulture professionals. When we mention ‘flower power’, this plant does not hold back! It was a solid patch of deep purple in the landscape all summer. Compact and clean flowers and foliage make this a winner. Try it out, we’re sure you’ll be a ‘fan’ of this flower!
Geranium Interspecific, Grace Ruby Red (P), Beekenkamp
What is more classic than a red geranium? This geranium has vibrant red colored flowers held above crisp, clean foliage on sturdy stems. The red color holds well in full, blazing sun, without fading or color melting. Grace Ruby Red has a nice, round, mounding habit that shows little to no Japanese beetle feeding!
Geranium Zonal, Galaxy™ Purple, Ball FloraPlant
If you haven’t heard of the Galaxy™ series, they are truly out of this world! This year, Galaxy Purple was the top performer. It produces large, sturdy ‘lollipops’ boasting dozens of deep violet-purple florets with a hint of white in the center. It consistently produced flowers all season on uniform, well-branched plants!
Dahlia, City Lights™ Purple, Selecta One
A multi-year winner—it’s that good! Bred for performance in heat, City Lights Purple lives up to expectations. Flowering through most of the summer with rich, deep purple flowers accentuated by the dark green-black foliage, holds up well in the full sun all season. The bees and other pollinators also love this plant.
Portulaca, Mojave® Mango, Proven Winners
Mango was the favorite in this collection of portulacas. The plants were vigorous and had a nice, low-growing form. The copious amounts of mango-orange-colored flowers, with a red center, opened by midday, providing waysides for many bees and pollinators. The whole planting of portulaca was abuzz! Great for massing in the front of the border.
Petunia (Vegetatively Propagated), Supertunia Mini Vista® Plum Veined, Proven Winners
This petunia performed well all year, from greenhouse production to the summer landscape—a floriferous plant, with quarter-sized flowers boasting light purple hues and contrasting deep purple-black veins. Although vigorous, the plants played well with their neighbors, not overgrowing their space. This petunia is a great massing plant that adds impact to the landscape.
Petunia (Seed Propagated), Easy Wave® Navy Velour, PanAmerican Seed
Another plant whose name is spot on! The rich, deep purple in the right light looks like the flowers are made of velvet. The large and numerous flowers hold their intensity in the full sun. These vigorous plants would work well for use in contrast with other plants, making them pop.
Container Winners
Combination Container, Playlist™ Uptown Funk, Sakata
This combination of three celosias was stellar in the garden! The container caught people’s eyes from across the garden. The vibrant reds, oranges, and yellows provided long-lasting, season-long color into fall. The sturdy plants filled out the container well. This combination would work well for fall planter interest!
Rudbeckia, SunBeckia® Graffiti Caramel, Bull Plant Genetics
Who doesn’t love a good caramel candy?! Another award winner from the Bull Plant Genetics SunBeckia lines. This Rudbeckia sports a unique caramel flower color, with the outer edges having a warm, rich, deep yellowish-brown color, and a deep reddish-brown eye. As the long-lasting flowers age, these colors develop a nice overall caramel color. The plants are relatively compact, keeping them from lodging—another great Sunbeckia to consider.
Mandevilla, Tropico Unico Pink, Ball FloraPlant
This non-vining type of mandevilla was stellar in the Colorado summer! Large, soft-shell pink flowers, with a rich rose and yellow throat, covered the stems for this containerized planting. The deep, glossy green foliage sparkled in the sun. A great upright shrub-like form to consider for the landscape!
Coleus, TerraScape ‘Queen,’ Kientzler North America
Talk about dramatic! This vigorous coleus can make a statement in your garden. The deep red maroon leaves with a blaze reddish-pink center, and lime-green shark-toothed edges are eye-catching! And the colors hold up well in full sun! The plants are sturdy and strong and work well in containers!
Geranium, Mojo™ White, Syngenta
Cloud-like cotton white clusters of flowers float above a deep green foliage. This plant has a mojo with lots of flower power—best displays when regularly deadheaded. Older flowers are not as noticeable as some other white flowered geraniums. It works well in containers and equally as well on the ground!
Scaevola, Scala Cappello White, Dümmen Orange
Another award-winning fan flower from the Dümmen group! Cappello White is a smaller-statured plant that works well in smaller containers. It produces crisp, clean, white flowers all summer long! It’s excellent planted on its own or mixed in container plantings.
Petunia (Vegetatively Propagated), Tea Flamingo, Beekenkamp
Plant a couple of Tea Flamingo Petunias to catch someone’s eye. This unique, flamingo peachy-salmon colored petunia flowered all summer, well after many other petunias started fizzling. It performed well not only in the container but also in the landscape bed. The plants were well-branched and had a more upright growth habit. If you try one petunia this summer, you should try Tea Flamingo. You wouldn’t be disappointed.
Petunia (Seed Propagated), Easy Wave® Navy Velour, PanAmerican Seed
One of the Easy Wave® series, which all performed well. This versatile petunia was also rated the best for our petunias planted in the ground. The large, velvety, rich, deep purple flowers glisten in the bright sun and don’t fade! The vigorous plants fill containers well and would be a good option for a mixed planter to fill out and spill over the edge. Catch this Wave at the garden centers this year.
Hybrid Impatiens (Grown in Sun), Sol Luna™ Light Salmon, Danziger
Sol Luna™ Prime series by Danziger performed well in the trials this summer. In full blazing sun, surrounded by brick and rock, these interspecific impatiens held their own! Prime Light Salmon was the top-rated one in the series with the most uniform growth. The classic New Guinea-like flower sports a delicate peach-salmon color and nearly 2″ wide flowers. These great hybrid impatiens handle the intense summer sun in Colorado but are also versatile for shadier situations!
Begonia (Grown in Sun), Stonehedge™ Rose Bronze Leaf, Benary
Impressive! Massive! Those were comments overheard from our evaluators. The Stonehedge™ series can grow to be hedge-like! These seed-grown, interspecific hybrid, vigorous plants filled our container well, making a statement.
It produced loads and loads of large, bright, rose-pink colored flowers that were juxtaposed against the deep bronzy-burgundy leaves. The pink-red colored stems echoed the flower colors throughout the plant. They handled the hot, bright sun and heat of the Colorado summer with no problems. If you want to fill in an area in the garden or make a small annual hedge, consider the Benary Stonehedge Rose Bronze leaf begonia!
Verbena, Empress® Sun Kiss Pink, Dümmen Orange
Pink, pink, pink. This relatively compact growing verbena was stunning with the copious amounts of medium-soft pink flowers that covered the foliage. The flowers aged well, with very little to no browning and fading. It was a showstopper through the whole summer and into early fall!
Angelonia (Grown in Container/Ground Bed), Guardian Angel™ Blue, Ball FloraPlant
Floriferous is an understatement! This is a stately triploid plant, boasting large, saturated blue-purple flowers. These plants started flowering in early summer and bloomed until the first frost. This snapdragon performed well in container and ground bed plantings, shooting out of the container like a mid-summer firework!
Lantana, Bandolista™ Mango, Syngenta
Mango was the best-performing Bandolista™ lantana. With loads of vibrant tropical shades of newly opened yellow flowers to reddish-orange older flowers, this lantana provides a great hot pop of color in the landscape. One can barely see the foliage when it is in full flower! With its moderate vigor and habit, it works well in containers and hanging baskets and can tolerate low water inputs. This plant will surely attract pollinators to your yard!
Calibrachoa, Bloomtastic Serenity 2025, Dümmen Orange
Compared to nearly all the calibrachoas trialed, Bloomtastic Serenity was covered in two-toned light purple with dark purple eyes and a yellow throat. It bloomed from early summer to very late in the season. When all the other calibrachoa had dwindled in color, this one was showy! Overall, the plant form was excellent, creating a nice display in the container. This plant lived up to its Bloomtastic name!
Portulaca, Mega Pazzaz™ Fuchsia, Danziger
Overall, the Pazzaz™ series did well in the trials. Mega was the top-scoring selection of the group. The Pazzaz™ Fuchsia produced bright, intense fuchsia pink colored flowers on semi-trailing stems. We observed that the portulaca in this series was open longer during the day, opening hours before and after other portulacas had closed. This portulaca was also a pollinator magnet, and with so many bees visiting, we could hear the containers humming standing feet away! Great option for container plantings, handling heat and drought conditions.
Begonia, Interspecific Hybrid (Grown in Shade; Ground bed/Container), Megawatt™, White Green Leaf, PanAmerican Seed
These begonias were developed for both sun and shade conditions. And they perform well in both! The clean white flowers with the bright yellow anthers and pistils contrast nicely with the glossy green foliage—great vigor in these plants, ideal for container and in-ground situations. Pink Megawatt™ also performed very well in the trials. If you want mega flower energy in the landscape, consider the Megawatts™!
Begonia, Elatior type, BK Collection Vermillion Red (P), Beekenkamp
Vermillion Red has been a consistent top-performing elatior-type begonia in the gardens! It boasts vibrant red flowers that pop in the part shade. Its upright habit makes it all the easier to enjoy the numerous silky red flowers. Check out this red begonia and the other colors in the Vermillion series!
Begonia, Boliviensis type, Florencio™ Yellow, Syngenta
The large, soft-butter yellow, brightly centered flowers of this Florencio™ contrast well against the deep, dark green lance-shaped foliage. The plants were very uniform and upright, creating an excellent container display.
Begonia, Tuber-type, Adora™ Velvet Red, Syngenta
Rich, velvety red, quarter-sized double flowers abundantly adorned the well-branched plants in the trials this year. The mounding-type begonias filled out the containers well. The crisp, dark green foliage provides a beautiful contrast to the red pops of color.
Interspecific Impatiens (Grown in Shade), Solarscape® XL Lilac Spark, PanAmerican Seed
The Solarscape interspecific impatiens performed well in both containers and landscape beds. XL Lilac Spark produced uniform plants with continuous flowering throughout the season. These seed series hybrids are versatile for the landscape, especially for those who want that traditional New Guinea Impatiens look, but in the full sun!
Other Outstanding Varieties
Anigozanthos, Kanga® Cherry, Green Fuse® Botanicals
This plant caught the eye of garden visitors this summer. This unique Australian native with velvety flowers was eye-catching and provided a rich cherry-red color for weeks on end! The iris-like foliage was attractive, complimenting and filling out the large container. Anigozanthos is definitely one to look for and consider for your landscape!
Echeveria gibbiflora, Coral Reef® Dark Chocolate, Green Fuse® Botanicals
Succulents have been popular for some time, and this echeveria performed well. The plants filled out the container nicely, and the aptly named plant provided great visual texture. This echeveria certainly is an excellent selection for containers on the patio!
Ageratum hybrid, Monarch Magic, Ball FloraPlant
Flowers, flowers, flowers. This ageratum performed well in both containers and the landscape. Unlike old-school ageratum, this one is better suited for full sun. It keeps flowering all season and is a surefire stop for pollinators, including bees and butterflies!
Helianthus, Sunfinity® Double Yellow, Syngenta
The epitome of “flower power.” This vigorous double-flowered sunflower boasts rich, 2 to 3-inch yellow flowers ALL summer and into the fall. This selection is well branching, so just a plant or two can fill a good amount of space in the landscape. If you’re putting it in a container on the patio, make sure to give it a big enough pot! Sunfinity Double Yellow also resists the pesky powdery mildew we often see with sunflowers.
Celosia, ‘Bright Sparks’ Series, Syngenta
Long-lasting, bright colors of deep red, orange, bright yellow, and intense pink can be expected with ‘Bright Sparks’! The wispy flower heads provide great color all summer, with minor fading. Excellent branching, sturdy stemmed plants that attract pollinators and love the heat of the Colorado summer!
Agastache Mexicana, ‘Summerlong™ Lemon,’ Darwin Perennials
One of several in the Summerlong™ series, Lemon stood out in the landscape this summer. This tender perennial started flowering in the greenhouse and didn’t stop all summer. It brings a nice bright spot of color, with lots of pollinator and hummingbird activity, and some fragrance. One would certainly get their money’s worth with this plant in the garden!
Hula™ Begonias, PanAmerican Seed
These interspecific begonias are quick to fill out in the landscape and in containers. These waxleaf begonias have a nice trailing and spreading habit that grows to about 12″ in the trials and provide lots of flower power! They are versatile, working well as massing plants in the border, for use in containers, and in hanging baskets in both sun and shade.
Evaluation
The trial evaluation was held in late summer. Judges, consisting of industry representatives, master gardeners, university employees, and trial garden advisory committee members, evaluated the plant varieties for performance using a combination of these criteria:
Plant Quality
- Uniformity of plant habit
- Bushy, well-branched shape versus open and leggy
- Healthy foliage (deep green versus chlorotic, yellow leaves)
- Foliage texture
- Disease resistance
Flower Quality
- Flower power (number of flowers per plant, substance, and holding power)
- Flower presentation (i.e. not hidden by the foliage)
- Color uniformity
- Stable color (resistance to fading) and stable pattern (for bicolor)
- Flower size and uniformity of flowers
- Balance of color in a mixture
Overall Presentation
- Overall “clean” look, versus visible spent blooms
- Fragrant flowers and/or foliage
- Good vigorous growth
- Resistance to climatic stress
- Novelty value of unique features
- Overall consumer appeal
Plant varieties were rated on a scale of 1 to 5 (1=very poor performance; 5=excellent performance). These numerical evaluations were used to calculate the average ratings for each variety in the trials.
Participants used their tablets or cell phones to electronically evaluate the plants. The pre-generated comments they could choose from included: Low vigor, Vigorous plant, Few flowers, Many flowers, Uniform, Non-uniform, Unique color and some chlorosis.