Greenhouse Canada

Plant resiliency put to the test

University of Guelph’s 2023 trials yield impressive results

February 5, 2024  By Rodger Tschanz

Capsicum Onyx Orange Photos: Rodger Tschanz

The following plant descriptions are of some of the best or most popular selections of annuals in the 2023 plant trials at the University of Guelph’s trial sites.  Most of the plant entries were trialled in both containers and in the landscape. 

The season’s growing conditions in our region of southern Ontario started of warm and dry but was followed by weeks of unseasonably wet weather before drying as we entered the fall.  The wet conditions contributed to increased disease pressure, especially in the landscape, and contributed to the leaching of nutrients from the root zone, especially in containers.  

The best plants from this trial were truly resilient to climatic abnormalities.  


1. Capsicum Onyx Orange
This ornamental pepper has dark purple foliage when grown outdoors in full sun. The fruit is shiny, and marble shaped; it’s coloured a dark purple black when unripe but then ripens to an orange.  It is a sister colour to the AAS award winner Onyx Red. The Onyx Orange seed in our trial was slower to germinate (by almost a week) than the Red selection. Both pepper cultivars have a similar, compact growth habit. Onyx Orange reached a garden height of approximately 30 cm with a spread of 35 cm. The ripening of the fruit coincides nicely with late summer where the colouration is a perfect fit for fall seasonal planters etc. This cultivar was very popular with visitors to the September trial garden. (American Takii)

2. Gazania Sunny Side Up
Brilliant and bright are the words I use to describe this new gazania from Benary. The brilliant bright yellow has white edging that highlights the dominant yellow colour well. Gazania blooms will often close under overcast and rainy conditions; this selection seemed less prone to do so than others in this year’s trial. (Benary)

3. Verbena bonariensis ‘Vanity’
This is a compact form of purple top vervain propagated from seed. By season’s end it reached height of approximately 1 m with a spread of 50 cm. It was a national AAS ornamental winner in 2022.  The compact, well branched form is suitable for container applications as well as in the landscape. This selection came out of VanHemert’s breeding program but is offered on the market through Benary with its ApeX seed treatment to break dormancy. We found the germination to be uniform, relatively quick and suitable for standard greenhouse production schedules. This was voted one of the Top 5 favourite annuals at the trial open houses in August and September.  As you can see in the picture, this selection is attractive to butterflies.(Benary) 

4.Helianthus Semi Dwarf F1 Orange Mahogany Bicolour
This seed propagated compact sunflower offers a new colour pattern to the variety of seed-propagated, season- long bloomers already available on the market.  The rich yellow of the ray floret petal has a splash of brown/mahogany colour at its base.  The intensity of the inner mahogany coloured ring on the inflorescence may vary with growing conditions. While this helianthus is a great addition to the annual garden bed, this selection is also suitable for large container applications with heights reaching a metre and spreading to 90 cm by season’s end.  (Takii Europe/Sahin) 

5.Coleus ColorBlaze Cherry Drop
This is a new edition to the ColorBlaze series. We grew this in both containers and in the landscape. Excellent vigour and performance. The leaves are small with smoothly toothed margins and tricoloured with chartreuse margins, followed by maroon and finally with a hot pink cherry centre. The growth habit is mounding and semi-trailing reaching garden heights of 50 cm with a spread of 1 m. Works well in containers or the landscape. (Proven Winners) 

6. Coleus Premium Sun Coral Candy
I’ve talked about this coleus series before.  It’s the first coleus from seed, that I have trialed, that can handle both shade and full sun growing conditions. Coral Candy has long, narrow foliage with shallow, serrated margins.  The colour pattern on the leaf includes a cream to pink centre with margins ranging from bronze to maroon; the leaves are outlined by a thin ribbon of green. In full sun, the intensity of the leaf coloration is more muted than in part sun. It tends to have an upright bushy habit but stays compact. Garden height when grown in full sun was approximately 20 cm with a spread of 25 cm. (PanAmerican Seed)

7. Coleus Volcanica Solar Flare
Last year Ball FloraPlant sorted its coleus offerings into named collections to better reflect their vigour and growth habit.  As you might gather from the name ‘Volcanica’, this collection contains plants that are vigorous and really make a statement in the garden.  Solar Flare, with its deeply toothed green margins and two-toned purple/cherry centre, is the first member of this collection. It is vigorous with garden heights over 50cm and a spread of 70 cm. (Ball FloraPlant)

8. Zinnia Belize Double Scarlet
In 2023 American Takii introduced a new zinnia series to join the ranks of the powdery mildew (PM) resistant Zahara, Profusion and Zydeco series. Belize is its name and at its introduction has three single colours and four double colours. I trialed Double Yellow, Double Orange, and Double Scarlet this past season. All three got through the season without PM infection. They also had excellent bloom performance. The three colours I trialed were well matched for size and vigour. Belize Double Scarlet was the most popular of the colours with the public. Garden height is approximately 40 cm with a spread of 60 cm. (American Takii)

9.Jamesbrittenia Safari Dusk
In 2023 we trialled both Jamesbrittenia Safari Dusk and Safari Sky.  Container performance was similar for both cultivars but of the two, Safari Dusk appeared to be the most resilient and demonstrated exceptional landscape performance under the wet growing conditions of 2023. This selection has large violet-coloured petals marked with dark purple or white near the base of the petal. The throat of the flower is a golden yellow. Garden height is approximately 24 cm with a spread of 80 cm.(Proven Winners)

10.Bidens Blazing Star
This selection of bidens has an inflorescence composed of yellow ray florets emblazoned with a red stripe down the middle. The red marking was consistent with a high degree of stability throughout the summer under the wide variety of growing conditions that were experienced. Blazing Star was another Top 5 favourite as determined by the public who visited the trials in the fall.  It has a slightly mounding habit reaching heights of 30 cm and spreading to 80 cm. Its performance was excellent in both containers and the landscape. (Danziger) 

11.Dahlia Darlin’ Abstract Fuchsia
Of the six colours in this series trial this summer, Abstract Fuchsia was the one to make the Top 10 popularity list as determined by visitors to the garden. Its double bloom has petals with a white base and pink/purple outer tips. This series had great all summer bloom performance but really stood out in the late summer and early fall.  Garden heights were 60 cm with a spread of 75 cm. (Danziger)

12. Cuphea SweetTalk Series
There are three colours in this new series of Cuphea procumbens: red, deep pink and lavender splash. Deep Pink is pictured here. These cultivars are well matched in bushy habit. I pinched our trial plants in the plug stage but based on observations of the same plants grown at another trial site without a pinch or growth regulator treatment, that pinch may not have been necessary to achieve the branching. It may be best for individual growers to experiment with cultural treatments that make sense for your situation. Based on my limited experience with SweetTalk, I tend to believe the genetics are forgiving and resilient. This is a pollinator friendly series was observed to be very attractive to bees. Garden height of between 40 and 50 cm with a spread of 50-70 cm. (PanAmerican Seed)

13. Lobelia Techno Deep Blue with Eye
This trailing lobelia exhibited exception performance throughout the summer of 2023 with its drought followed by high rainfall and high temperatures. It exhibited great heat tolerance and bloomed continuously through the summer. Based on our experience, this is great choice for both containers and the landscape. The white eye in the blue background of this flower contrast well helping it to stand out in the landscape. Garden height of 30 cm and a spread of 65 cm. (Syngenta Flowers) 

14. Petunia Itsy Pink
The new addition to the Itsy series is pink and small; now there are pink and white colour options for this series. The summer performance in containers was amazing in 2023.  If you’re not familiar with this series, it’s worth giving it a try. Bloom diametre of the Itsy series is smaller than many calibrachoa cultivars but with the petunia genetics that tends to be more forgiving of different growing conditions such as higher soil pH. Garden height of approximately 27 cm and a spread of 50 cm. (Syngenta Flowers)

15. Verbena Superbena Pink Cashmere
Here’s another wonderful colour to add to your choices of trailing verbena for both containers and landscape. Superbena Pink Cashmere is both vigorous and heat tolerant and reliably produces blooms that open as medium pink, and fade to a light pink with age. There’s something about this colour combination that never failed to grab my attention when in the garden. Garden height of 37 cm with a spread of 120cm. (Proven Winners)

16. Canna Cannova Rose Dark Bud
This is a compact seed propagated F1 hybrid canna bred by Takii and marketed by Ball Seed. This was voted as one of the Top 10 favourites in the trial beds in September. The dark buds and rose-coloured petals contrast well against the dark green foliage. This proved to be a great choice for both the landscape and container applications. Expect garden heights of approximate 1 m and a spread of 80 cm. (American Takii)

17. Lantana PassionFruit
It is always gratifying to see a new plant live up to the hype that is thrust upon it in the spotlight of CAST and elsewhere. That was certainly the case for this new lantana which has a dramatically different habit from the other lantanas in the trial. It is low growing and spreading with great bloom performance. This selection was in the Top 5 picks by visitors to the 2023 trials. With its spreading habit it is a great choice for both landscape and container applications. We saw it reach heights of 16 cm and spread to 80 cm in the tirals.(Ball FloraPlant)

18. Euphorbia (Chamaesyce) Star Dust Super Flash
This filler plant has medium vigour with a mounding/semi trailing habit and with large, densely arranged floral bracts. Garden height was approximately 20 cm with a spread of 30 cm. Container height was approximately the same at 20 cm. (Dümmen Orange)

19. Euphorbia Euphoric Double White
This selection is another dense grower with a high concentration of bracts per unit area. It has a mounding habit and by the end of the season can be seen to grow in an almost sculptural way (see photo). In the late season, the brilliant white bracts can develop a pinkish blush. Observed height in containers was over 30 cm. In the landscape it was over 25 cm with a spread of 40 cm. (Syngenta Flowers)

20. Euphorbia Glamour
The most vigorous selection of Euphorbia in the 2023 trial was the seed propagated Glamour. This selection reached heights of 61 cm with a spread of 70 cm in the garden by summer’s end. It has a much more open look then the two vegetatively propagated cultivars previously mentioned. It is a great choice for the landscape as well as for blending with other vigorous growers in mixed containers. (PanAmerican Seed)

There were many more trial entries that deserved comment over their summer’s performance and then there are the perennials that had an exceptional year. More on these in an upcoming edition of Greenhouse Canada. In the meantime, stay tuned for more information about the upcoming 2024 trial season. 

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