By Judy Hominick
f we can’t kill it in Texas, no one can," says Jimmy Turner, director of horticulture research at the Dallas Arboretum, during the annual Plant Trials Field Day held at the arboretum this past June. Every year, the arboretum grows and evaluates plants in the trial gardens to showcase plants that have stood the test of our drastic Texas climate. The arboretum also works in cooperation with Texas A&M University on trials for the Texas Superstar, EarthKind Roses, North Texas Winner’s Circle and CEMAP (Coordinated Marketing and Assistance Program).
This year, the Field Day was entitled "Trial by Flower" or as Turner likes to say, "Texas tried and true or fried and through." As Turner pointed out and as most gardeners already know, Texas is hotter, windier, drier and sunnier than nearly anywhere else in the United States!
Since our seasons vary so much from year to year, plants are evaluated over several years and the winning plant selections have proved they are tough enough to not only survive but to flourish in Texas landscapes. Many of the plant varieties tested in the trial gardens are new to the horticulture trade, so the trials provide vital information to commercial plant producers and, ultimately, to home gardeners.
Home gardeners will be glad to hear the arboretum prepares their garden beds using a method most home gardeners can follow.
"We amend the soil with compost, shredded bark mulch and expanded shale," says Turner. "This is what we recommend to home gardeners with heavy black clay soils."
One of the goals of the trials is to find plants that will do well under low maintenance conditions. The arboretum uses a standard granular high nitrogen fertilizer at the initial time of planting and does not use liquid feed or repeated fertilization during the growing season. Since winning plants must also be resistant or tolerant of insect pests and disease, insecticides and fungicides are not used to treat plants in the Trial Garden.
Finally, plants are watered only as needed with an overhead sprinkler system just like the ones used by home gardeners.
COOL SEASON TRIALS 2006
The cool season trials covered hundreds of pansies, violas, dianthus and snapdragons as well as other "pansy partners" that will work for fall/winter gardens. Plants are rated in a number of categories that included many factors – length of bloom, vigor of plant, quality and color of flowers and how the plant fared after freezes or hard rains.
Though most gardeners will go for the pansies that sport the biggest blooms, Turner prefers the medium sized pansies with his favorite being the ones from the Nature series. The flowers come in seven different colors or color combinations and the blooms stand just above the compact foliage. The plants were quick to recover and re-bloom after freezes. At the arboretum, these durable plants grew nearly a foot tall and were full of blooms all season.
For medium sized blooms, the Pansy Springtime series performed well in the last two years of testing with consistent high scores and lots of flowers that come in a wide spectrum of colors.
The Mariposa series proved to be another solid performer with huge 2-inch to 2.5-inch blooms with lots of great colors like rosy sunset and peach shades. It was pointed out, though, that the Colossus series still sported larger blooms at the arboretum.
For a pansy that shows up well from a distance, the ‘Panola Violet Picotee’ with its medium sized flowers had great color and earned winning marks.
A pansy that Turner promotes and hopes will be grown more is the ‘Purple Rain’ and the purple and white ‘Frosty Rain’ pansies. Both are vigorous growers and will work great in the landscape, containers or hanging baskets.
For the biggest impact as far as flower coverage and length of bloom, the Arboretum found violas to be the winners.
"The viola ‘Gemini’ series is still one of my favorites and is a heavy, heavy bloomer," reports Turner.
This is a vigorous plant less than a foot tall with bicolor flowers that are either a cheerful purple and white or purple and yellow color.
Perfect for containers, Turner recommends viola ‘Amber Angel Kiss’ for an extremely compact, cold tolerant plant that blooms in 33 unique colors ranging from yellow/orange to maroon.
For the best pure orange viola and lots of blooms, try the ‘Penny Orange’ viola. The ‘Penny Red with blotch’ will give you deep red bronze flowers that work well in combination plantings.
Pansies and violas are not the only plants gardeners can turn to for color in the fall and winter months and the Arboretum evaluated a number of "pansy partners" gardeners can utilize.
For some great mixed color blooms in late spring for a shady garden, try planting Aquilegia ‘Origami: series’ in the fall.
"They will be dead by June but will stop traffic when in bloom," says Turner.
Though Aquilegia, often known as columbine, is a perennial, this variety should be considered an annual here in Texas.
For the sunny or part shady fall garden, Dianthus is a good choice and over the last two years, the arboretum trialed two main species – the Dianthus barbatus types with tighter flowers and taller stems and the shorter Dianthus chinensis types with open flower heads. Both are considered short lived perennials or biennials and are used as annuals in Texas gardens. Overall, the arboretum found that the chinensis types outperformed the barbatus types. They bloomed for a longer period of time, had better overall quality and grew back and bloomed better after being cutback.
The best scoring Dianthus historically was the pink and white Dianthus ‘Ideal Select’ for its great flowering and habit. Also getting high marks was the Dianthus superbus ‘Kawara Mix,’ which grew 3 feet tall in the garden and gave 6 to 8 weeks of lacey, scented blooms with no staking needed. If you want flowers that bloom to form a "meatball" of flowers, the Dianthus ‘Amazon’ would be a good choice. This bloomer is best planted in the fall and makes a good cut flower.
For something a bit different, the arboretum had good luck with the fragrant Erysimum ‘Citrona Orange’ in a sunny location for blooming throughout the winter. Linaria ‘Enchantment,’ another sunny annual with fall and spring flowering, also passed the test. The flowers are magenta with a golden yellow and white center and do well in containers.
"This one has been through 19 degrees and the flowers burned off, but foliage remained good," reports Turner. "Two weeks later, it was in bloom again."
For a snapdragon with non-typical flowers, try Snapdragon ‘Bells’ with its compact habit and a growing height of 10 inches. The open butterfly type pink flowers bloomed for several weeks. Snapdragon ‘Montego Orange’ had very rich, deep bloom colors on plants that grew 8 to 10 inches with a multi-branching habit.
For summer flowers, the arboretum tested 1,440 total varieties of annuals, perennials, foliage plants and some tempting "Best un-new-usual" plants. Fortunately, the winners were numerous.
Though usually skeptical of ageratum, Turner admits he likes the Ageratum ‘Artist’ a lot. Other ageratums in the trials scored higher, but this series lived the longest. Flowers come in blue and purple and a rose color.
Angelonia ‘Serena’ series was a winner on several lists – it was one of the top 10 best annuals and was named a 2005 North Texas Winners Circle Award.
"This was one of the absolutely best Angelonia and did not need staking," says Turner of this compact, heavy flowering annual with lavender pink, purple or white flowers.
Gardeners have often found Celosia to be one of those plants that die shortly after it is planted, but Celosia ‘Fresh Look’ made it to the 2005 North Texas Winners Circle. It also got a nod from Turner who confessed he used to hate this plant. With red, yellow, orange and gold flowers, this Celosia bloomed continuously at the arboretum and withstood the heat.
To complement the other sun loving plants in your garden, Euphorbia ‘Diamond Frost’ would be a good addition with its fine textured foliage and white flowers that withstood heat and humidity with no problem.
"Euphorbia is perhaps one of the most underused plants," says Turner. "Think of it as ‘Baby’s Breath’ for the south."
Named the best new introduction in 2005 and a 2005 North Texas Winners Circle was Helenium amarum ‘Dakota Gold.’ This Texas native is one tough plant that is deer and animal proof and forms mounds of gold flowers all summer long. Also known as sneezeweed or bitterweed, this plant has thread-like aromatic foliage and is so tough, it can be found growing in the cracks of highways.
Impatiens is always a favorite for shade gardens and more testing will be done next year at the Arboretum. Turner did comment on a new favorite he found this year in the ‘Trailing Spellbound’ series, which comes in multiple colors. This plant has trailing horizontal branches which makes this long blooming annual perfect for hanging baskets.
Petunia ‘Tidal Wave Silver’ remains the number one scoring petunia with silvery blooms with purple center. This petunia gets big – up to three feet across – and lasts through the heat better than any variety and is cold tolerant, too.
If you need an unusual annual for the shade that will have both flowers and great foliage, try Porphyrocoma ‘Maracas’ Brazilian Fireworks. This tropical has variegated foliage with bicolor pink and purple flowers.
"The flowers are awesome, but the foliage makes it a worthy garden addition alone," reports Turner. "The darker the shade, the better the plant grows."
Salvia lovers might want to try Salvia ‘Mystic Spires Blue’ as Turner cannot say enough about this plant.
"This is my best new introduction for 2006," says Turner. "Best blue saliva I’ve tested."
‘Mystic Spires Blue’ is basically a dwarf form of Indigo Spires and only reaches 12 to 14 inches in height. Turner suggests it be used as an annual or perennial.
For a fast growing shade plant to compliment impatiens, Alternanthera ‘Party Time’ was chosen as a 2005 Winner of North Texas Winners Circle Award. This Alternanthera colors up more in the summer and can ramble to 10 inches. For an Alternanthera that will grow in sun (or shade), consider ‘Red Runner,’ which Turner says is like a smaller ‘Purple Knight.’ It reseeds and will grow anywhere – from dry garden spots to a bog.
Need something really big and bold with dark burgundy foliage all summer long that does not fade? Try Hibiscus acetosella ‘Maple Sugar’ – a plant that Turner calls "a beast." It grows to 5 feet and can be pruned if it gets too large. A heat lover that thrives in full sun, ‘Maple Sugar’ flowers more than the typical species.
Another flame proof plant for the sun is the Pepper ‘Black Pearl’ with its attractive deep purple, nearly black foliage that grows to 3 feet. ‘Black Pearl’ was named to the 2005 North Texas Winners Circle and gets its name from the fruit that eventually turns black. This pepper definitely comes with a warning from Turner.
"They are edible, but will melt your tongue right out of your mouth!"
Calling it "absolutely the best shade plant for Texas," Turner recommends Asarum splendens – Chinese Wild Ginger. The evergreen deep green foliage is splashed with silver and thrives (and reseeds) in dry shade where it makes a great groundcover.
A perennial that loves the heat and will add a different element and color to the garden is a blue love grass – Eragrostis elliottii ‘Wind Dancer.’
"This is a great, open plant," reports Turner. "The hotter it gets, the bluer it gets."
This drought tolerant fine textured grass grows to 4 feet and looks great in big containers.
For the gardener looking for a Monarda that won’t succumb to mildew, the trial garden has found one that is mildew resistant – Monarda bartletti x fistulosa ‘Peter’s Purple.’ Turner says it is the best monarda he has ever grown and though it grows to 6 feet tall, it does not fall over. ‘Peter’s Purple’ has a long blooming season with vibrant purple flowers and color bracts for three to four months.
BEST UN-NEW-USUAL PLANTS
If the gardener wants to grow something that his gardening friends do not have – and who doesn’t – check out some of the unusual plants trialed at the Arboretum.
If you thought you saw what looked like a different colored Mimosa at the nursery, you were not mistaken. Albizia julibrissin ‘Summer Chocolate’ is a Mimosa with the same usual hot pink flowers but whose foliage is a pretty burgundy color. It is still considered a short-lived tree with a lifespan of about 15 years but is pretty enough to consider for a sunny spot.
If you have always wanted the tropical look of a banana tree, Banana ‘Bordelon’ is a big plant that actually blooms – though the fruit will not ripen before fall. A fast grower, the burgundy tinted leaves will not tatter as bad as other varieties and will return the following spring.
Begonia withlacoochee is a tropical shade plant with burgundy and gray/green foliage and continuous white flowers. Perfect as a container plant where one plant can grow to 3 to 4 feet of trailing foliage and blooms.
If it you want something different than Caladiums for the shade, Turner recommends Syngonium ‘Neon Tetra’ as a better choice. With pinkish leaves, the color continues to get better all summer and, best of all, will not crater in the heat.
For a truly striking plant for dry or moist shade, try the quick growing Stromanthe sanguinea ‘TrioStar.’
"If you want something bright and showy in the shade, use this," says Turner.
The plant is quick growing, with tropical leaves that are a vivid red on the undersides while the top of the leaf has white and green variegation.
Gardeners are welcome to visit the Dallas Arboretum Trial Gardens to see the plants firsthand. According to Turner, most other trial gardens in the country are not open to the public.
"Most trial gardens are run by private seed and plant breeding companies or universities and don’t allow access to the general public. This is one of the few trial gardens that can be easily accessed by homeowners, horticulturists, landscapers and commercial growers alike. The Dallas Arboretum also does not charge the breeders to trial their product, allowing us to be a non-biased trial site."
For inspiration and to see trial summary information and color pictures of all the plants mentioned here plus many more, visit www.dallasplanttrials.org