Highlights From the University of Tennessee’s Summer Plant Trials
December 19, 2023 Note: Information for this trials report comes from Jason Reeves, curator of the University of Tennessee Gardens.
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We trialed more than 165 varieties of annuals, perennials, vegetables, and herbs in 2023. Trials were planted during the month of May, and data was collected at regular intervals between the months of June-September. Overall, the growing conditions were good throughout the season. Temperature and rainfall were average throughout the growing season. Supplemental overhead irrigation was used as needed especially in late summer when conditions became dry.
Our biggest challenge this year was a lack of labor. We cannot find interns/summer student worker. Our Master Gardener volunteers came to our aid. We even put some on payroll.
Here are a few plants that stood out to me this year:
- Bidens ‘Campfire Marshmallow’ (Proven Winners) – A vigorous performer, producing a never-ending abundance of white blooms with yellow centers. Unlike other Bidens, which struggle with the heat and humidity in our area, Campfire Marshmallow continued to produce a profusion of blossoms on densely mounded plants throughout spring, summer, and fall. They require no deadheading and only occasional watering once established. Attractive to pollinators, they spread 20 to 24 inches wide, 12 to 16 inches tall, and thrived in full sun.
- Nemesia ‘Aromance Mulberry’ and ‘Aromance Pink’ (Proven Winners) – The Aromance series is another plant that has surprised us with an uncharacteristic vigor for its genus for the second year in a row. From the time we potted up plugs in March until the killing frosts claimed them in the garden beds, this plant was a winner. They reached 10 inches tall and 18 feet wide. Despite our heat, it continued to flower with the temps in the 90’s with no deadheading or cutting back. And let’s not forget the fragrance, a lovely mix of vanilla and baby powder.
- Verbena ‘Lascar Orange Lava’ (Selecta One) – Excellent glowing orange-red flowers lay flat to the ground and spread about 12 to 16 inches; in pots it grew a bit taller at 6 to 12 inches. This verbena is eye-catching in the landscape because of its unique flower color; it bloomed reliably from spring until frost. The compact habit of this verbena made it perfect for our parking lot pots. It thrived in full sun, bloomed continuously, and growth was more compact than other verbenas making for a neat tidy look.
Other high-rated plants included:
- Petunia ‘Supertunia Hoopla Vivid Orchid’ (Proven Winners) – This picotee-patterned petunia shows off a profusion of bright purple flowers with crisp white edges. Their cheerful and bold look works well as a spiller in mixed containers and in the front of the flowerbed. They are a continuous and prolific rebloomer, attracting pollinators from planting until hard frost. They grew 4 to 8 inches in height and spread 20 to 24 inches in our flowerbed.
- Petunia ‘SweetSunshine Pink+Red Vein’ (Selecta One) – We loved this semi-trailing, double petunia in our mixed container pots. Unique pink and red veined color on flowers with a cute swirly center stood out on top of medium-green foliage. These durable, heat-tolerant plants maintained their color and form from spring until frost. Doubles typically don’t last all summer for us, but this one performed exceptionally well.
- Vinca ‘Soiree Kawaii Paprika Red’ (Suntory) – We love all the Soiree Kawaii vinca series and can’t say enough good things about them. They are like no other vincas on the market. A profusion of red micro-blooms with white centers, they continued to bloom reliably from planting in spring until frost. This new addition to the colorful Kawaii series can be used to create a showy border or mixed into containers. They enjoy full sun and well-drained soil and work well at the front of the border where they can shine. Compact but vigorous, with glossy green foliage.
- Sweet Potato Vine ‘Sweet Caroline Upside Black Coffee’ and ‘Sweet Caroline – Upside Key Lime’ (Proven Winners) – Both cultivars possess a strong climbing habit and make an impactful statement. Three plants of each cultivar were planted at the base of a 10-foot tall by 4-foot wide trellis. Black Coffee overtook the trellis faster, but the combination was beautiful with hints of Key Lime shining through. The trellis was completely covered by the end of July. For future planting the ratio of Key Lime should be greater than Black Coffee.
- Petunia ‘Supertunia Mini Vista Ultramarine’ and ‘Supertunia Mini Vista Midnight’ (Proven Winners) – We were impressed with the entire Supertunia Mini Vista series this year. We planted all of the series in the ground and they all performed well, blooming heavily from spring until frost. They thrived in full sun with occasional watering in the peak of summer and created a colorful, solid groundcover, attracting many bees and butterflies. The two types we highlighted above were especially attractive: ‘Ultramarine’ had deep purple flowers and ‘Midnight’ stood out as well with deep plum-colored blooms, that turned nearly black towards the center.
- Verbena ‘Superbena Pink Cashmere’ (Proven Winners) – The large umbels of delicate pink flowers on this verbena won our hearts, with its extreme vigor, producing loads of blooms all season without deadheading. Mounded trailing plants were attractive to bees and butterflies, provided interest all warm season. This sun-loving plant is deer resistant and disease resistant, making it an easy choice for containers and flowerbeds. It grew 12 to15 inches tall and trailed 24 to 30 inches in our trial bed.
Full trial results are available at west.tennessee.edu/ornamentals. Learn more about other field trials from 2023 here.
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Highlights From the University of Tennessee’s Summer Plant Trials
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