2020 trial garden results from Colorado State, Smith Gardens and more

Check out more trial results from around the United States.

November 21, 2020

To see the new varieties published in the December issue of Greenhouse Management, click here.

Colorado State University

Trial garden manager: Dr. Jim Klett


Best Overall Performance, Annual – Dahlia ‘Lubega Dark Velvet’ from Benary+


This was a ‘showstopper’ due to the strong contrast between the dark purple/velvet foliage and beautiful bicolor blooms. Plants were extremely attractive with the dark foliage coloring and uniform compact growth habit.  The prolific flowers were held high above the plants to create maximum show. Blooms had single petals which attracted many bees.


Best Heat-tolerant Annual - Lantana ‘Hot Blooded Red’ from Syngenta


Vibrant flowers had at least 3 different colors that ranged from deep red to tangerine. Plants had a beautiful and uniform growth habit with abundant flowers on top of plant producing a lot of flower power.


Best Pollinator-friendly Annual - Salvia ‘Mystic Spires’ from Ball FloraPlant

Dependable flowering and great growth habit made this a winner both in 2020 and in previous years. Vigorous plants were stately and upright with abundant dark purple flowers. Foliage was clean and glossy. This was another bee friendly plant that was often buzzing with excitement with pollinators.


Best Drought-tolerant Annual - Vinca (ground) ‘Virtuosa Lavender’ from Sakata


Plants were vigorous and produced abundant large, soft lavender flowers that had a white eye for added interest. The compact and uniform plants did well in the ground but would probably also look great in a container.


Best Overall Performance and Best Pollinator, Perennial

Millenium Ornamental Onion from Eason Horticulture Resources and Stonehouse Nursery

(Allium hybrid)

This was a definite “showstopper” plant that was described as having an “insane” amount of blooms.  Flowers were a nice shade of pink and were a favorite of many bees and butterflies.  The flowers combined well with a nice compact plant with clean foliage and very uniform growth habit. 

Best Heat-tolerant Perennial – Bandwidth Maiden Grass from Darwin Perennials

(Miscanthus sinensis)


This is a good selection for smaller gardens and landscapes as the plant maintains a nice uniform habit that is only 3-4’ in height.  Plants did not bloom but foliage is attractive with yellow stripes running across the blade.  The variegated foliage did not revert and was impressive all three seasons. 

Best Drought-tolerant Perennial – GRANITA Orange Ice Plant from Plant Select®


Bright, iridescent orange flowers blanket the plant creating an impressive show of flower power.  Large flowers bloom over a long period.  Plants make a very attractive ground cover as the beautiful green foliage forms a nice dense mat that hugs the ground.  Vigor is excellent and makes a good spreader.

Smith Gardens

Trial garden manager: Melissa Maguire

Best overall performance

Annual - Petunia Bee’s Knees (Ball Floraplant)

This Petunia really is the “bee’s knees” – its large flowers boast the brightest, most saturated yellow we’ve seen on a Petunia, only slightly fading toward the edges. The plant also has deep green foliage and a strong, sturdy habit that holds up well in the landscape and also performs well in baskets and containers. A favorite all around this year!

Perennial – Echinacea Sunseekers Double Rainbow (Flamingo Holland)

If we could sum this plant up in one word: amazing! This new Echinacea variety performed fantastic for us in the garden this summer. We loved the double flowers that opened a salmon-pink color then changed as they matured, giving different shades of color on a single plant.

Best drought-tolerant

Annual – Portulaca Mega Pazzaz series (Danziger)

Portulaca can handle drought with the best of them, but what made this series stand out from the rest was that the flowers were open even on cloudy days! This is a big deal for us in the Pacific Northwest and definitely got our attention. Here we picture Mega Pazzaz Dark Pink in a patio combo with large bright flowers open on an overcast day

Perennial – Sedum Mojave Jewels Ruby (Pacific Plug & Liner)

Sedums are a great choice for drought-tolerance and we especially loved this series from PP&L. The Ruby color was our favorite, with deep purple/blue foliage that gets absolutely covered in deep red flowers later in summer.

Best pollinator-friendly:

Annual - Cuphea Hummingbird’s Lunch (Dummen Orange)

Aptly named, Cuphea Hummingbird’s Lunch is a pollinator magnet. Hummingbirds were dining all summer on these baskets, which held up under heat and drought and looked great all year.

Perennial – Agastache Poquito series (Terra Nova Nurseries)

Bees love Agastache and the Poquitos are no exception. Terra Nova created a basket concept with their Poquito line and we were loving them this year in the garden. Plants were well-branched, easy to care for, and bees were all over the continuous flush of flower

Best heat-tolerant:

Annual – Lobularia Yolo Vanilla Pink (Dummen Orange)

Our area is not a great test for heat tolerance, but we had a standout Lobularia in the garden that looked fantastic all summer – Yolo Vanilla Pink. Perfectly mounded plants covered in flowers continued to look great as temperatures climbed in the summer. A beautiful, unique color of Alyssum.

Perennial – Lavandula stoechas ‘Primavera’ (Darwin Perennials)

The new Primavera Spanish lavender from Darwin was a knockout in the garden, with huge dark purple flags on a nice compact mounded habit. The flowers kept coming all summer with no deadheading. A winner!

University of Minnesota’s top-10 varieties

Trial garden manager: Steve Poppe

Angelonia Aria Blue performed exceptionally well in both a container and in our garden landscape. Excellent uniform habit with good overall growth. Slightly larger plant, good flower stem strength and more flowers than the other 12 Angelonia cultivars we trialed in 2020. Height = 12‐16” Spread = 10‐12” Bloom Time = Late Spring to Late Summer Exposure = Full Sun

Begonia Dreams Garden Macarouge flowered relentlessly all summer long with numerous eye‐ catching single, scarlet‐red blooms with a yellow center plus clean dark green foliage. Excellent performance in our shady garden with minimal maintenance. Does best if grown in a container. Height = Up to 14” Spread = Up to 10”

Bracteantha Granvia Gold is a strawflower that had large bright yellow flowers and a center that turns orange as the flower ages. Trialed in a large block planter and exposed to very warm temperatures. These vigorous growing plants were resistant to mildew, a common disease found in earlier strawflower cultivars. Can be grown as a cut flower for fresh or dried displays. Height = 18‐30” Spread = 18‐24” Bloom Time = Spring to Fall Exposure = Full Sun

Gomphrena Truffula Pink is the most outstanding feature of this cultivar was how early it flowered as compared to other gomphrena varieties we have trialed in the past. Had a well‐balanced habit that showed off numerous hot‐pink flowers that covered the plant. Truffula® Pink is a tough and durable plant that is easy to care for and requires no deadheading. Attracts many bees and butterflies. Can be used for cut and dried flowers. Height = 22‐28” Spread = 22‐26” Bloom Time = Late Spring to Fall Exposure = Full Sun

Marigold erecta Big Top Yellow is a very easy to grow marigold that has abundant fully double yellow blooms all summer long. Big Top™ Yellow is a vigorous cultivar with no disease issues and is well‐suited to challenging weather conditions. Occasional deadheading the old flowers will keep new buds coming, and you'll get even more color. This marigold is perfect for the gardener looking for an easy‐to‐grow annual from seed. Height = up to 30” Spread = 16‐24” Bloom Time = Spring to Fall Exposure = Full Sun

Petunia Amore Queen of Hearts is a unique bicolor petunia with red and yellow striped petals that displays five red hearts on each 2 1/2” blossom. Queen of Hearts has a semi‐trailing habit that grew exceptionally well and was smothered in eye‐catching flowers in our 2020 garden bed. Height = 8‐12” Spread = 12‐24” Bloom Time = Spring to Fall Exposure = Full Sun

Petunia SuperCal Rose is a unique blend of petunia and calibrachoa that maintained bright vibrant flowers with no fading. This petunia had exceptional performance in both a hanging basket and in the display garden beds. Performed well all season, had numerous blooms, and bounced right back after a rain. No deadheading needed. Height = 14‐24” Spread = 14‐32”Bloom Time = Spring to Fall Exposure = Full Sun

Scaevola Surdiva Blue Violet withstood our summer heat and provided continuous color throughout the season. The semi‐trailing habit is easy to grow and maintain in a hanging basket. Besides the outstanding blue violet flower color, the foliage remained bright green throughout the entire summer. Height = 6‐10” Spread = 18‐24” Bloom Time = Mid‐Spring to Fall Exposure = Partial Sun, Full Shade

Vinca Valiant Orchid had superior garden performance in 2020. Its most outstanding feature was the uniformity of all the plants in our garden bed. The showy lavender star‐shaped flower blossoms with a white eye created a striking look in our full sun garden location. Its glossy leaves remain dark green in color all season long. Vincas will do well if you can provide plenty of sun, heat and drier conditions. Height = 14‐20” Spread = 10‐12” Bloom Time = Spring to Fall Exposure = Full Sun

Zinnia Double Zahara Yellow Improved features fully double, large bright yellow flowers with a very compact bushy plant. The flowers sit atop the clean green foliage and made a bold statement in our garden beds in 2020. For optimum performance, plant zinnias in a well–drained garden soil and occasional deadhead to improve appearance. Height = 16‐20” Spread = 16‐20” Bloom Time = Spring to Fall Exposure = Full Sun