University of Florida Field Trials

October 10, 2002 - 09:25

Warm climate performance of vegetative annuals.

Let's face it, climates are different in Florida, Michigan
and Colorado, which can generate some very different results from trial
gardens. What succeeds in high heat and humidity may not succeed under cool
nights with low relative humidity, and vice versa. So patronize your local
trials gardens and make a point of learning their results; it's the best any
grower can do if they are concerned about local performance.

Compiled ratings from trial gardens around the United States
can, however, be a great "Big Picture" source. But remember that a
northern garden's recommendations may only be good for spring or even winter
performance in the South. On the other hand, a summer rating in Florida will
indicate to northern growers that a plant has an extended season where summers
are hot.

The spring field trials at the University of Florida this
year contained 180 cultivars of vegetative annuals, both those more common to
southern production and also several focus areas. Focus crops for these trials
were: seed-produced spreading petunias, vinca major (periwinkle),
"perennial" verbena, vegetative torenia, helichrysum, cuphea species,
porter weed, calibrachoa, plectranthus, vegetative catharanthus (vinca) and
vegetative coleus. (Information about helichrysum and vinca major can be found
in the August issue of GPN.) The trials extended from April 15 when plantings
began to August 7 when crops that were past landscape value were removed. We
still have about 70 cultivars in the gardens as of September 10 that are going
strong, but more about that later.

The goal of these trials is to promote plants that are
tolerant of extreme high heat and humidity, conditions common across the
southeast sunbelt from Florida to West Texas. Obviously, the season here begins
very early in the year and, for some plants, ends a lot earlier as well. The
results of these trials can be used to help growers refine their late-season
selections where heat and humidity have the biggest impact on crop quality.

Trial Essentials

How we set up our trials. normal'> Three 120- x 8-foot trial beds were installed in a full sun and
turfgrass area with established bermuda and bahia grass. The area had not been
worked previously and was amended with mushroom compost at 1 yd3/100 ft2. Soil
pH ranged from 5.2-6.6. Amending the soil brought the pH up to 6.0-6.8.

Twelve plants of each cultivar were grown from liner to
4-inch pot in our greenhouses. These plants were planted on 1-foot spacings,
and received nine grams of Osmocote slow-release 18-6-12 fertilizer (3-month
formulation) incorporated into each planting hole. Beds were mulched between
plants with Cypress mulch at an average depth of 4 1/2 inches. Beds were
irrigated using commercial drip tape and watered twice each week. Throughout
the season, no other fertilizer, fungicide or pesticide was applied.

What we measure. We
keep track of first flower date, peak flower date, the time it takes to form a
canopy over the test plot, vigor and visual quality (0 = dead, 1 = poor, 2 =
fair, 3 = OK, 4 = good color and display, 5 = excellent, of superior quality).
It can be roughly stated that any plant with a 2 or lower rating is not
considered worth the effort needed to plant it. But remember, these are field
trials, not greenhouse or container trials; performance under the two can be
very different. The biggest factor affecting outdoor performance in Florida is
rain. Our rains are usually in the afternoon and completely wet the foliage as
the sun is setting, a recipe for disease.

How we report our findings. normal'> Our trials are online at; just click on the
"new" button and select spring trials. The focus crops are all
photographed every other week, allowing you to virtually watch the plants grow
throughout the trial.

Trial summary. This
was a dry spring and early summer in Gainesville, which really extended the
season for a lot of the cool, dry preference crops. When our rains began in
June, the differences became very obvious in terms of what can take heat and
humidity and what can't. Even so, there were a lot of surprises with crops that
held on and looked good long past the onset of rainy weather. Even now, almost
a month after the trials are completed, Helichrysum petiolare still looks
pretty good, which no one expected.

Seed-produced trailing petunias

This type of petunia grows more popular each year, and every
one of the trialed cultivars had a period of weeks where it rated a perfect 5.
So there were no losers in the group. All began to deteriorate around week 26
when the rains kicked in.

Wave Purple (Pan
American Seed) received the highest average rating for the season (trial ended
week 26). The Wave series is definitely the most heat-tolerant and
long-flowering. Good colors and a low spreading habit. All cultivars clung
tightly to the ground and persisted longest into the heat.

Ramblin' Lilac Glow
(Goldsmith Seed) was the earliest-flowering in the landscape. This variety had
a more mounding habit, with good-sized flowers and a quick growth to cover the
trial plot. This growth habit caused it some problems later in the season with
lodging, but all in all it was a good early-season performer.


Yeah, yeah I know I talk too much about these plants, but we
had 22 releases in the trial this year, and there were some interesting
results. Really; there were.

Plectranthus madagascariensis normal'>, also called P. coleoides 'variegatus' and P. iboza 'coleoides'),
whatever; they are all the same plant (EuroAmerican, HMA and my mother's
garden) and all were basically the same in their performance, which was solid
with great uniformity and foliage color through the season. These plants are
still holding strong.

Plectranthus 'Nicoletta' normal'> (Ball FloraPlant) has silvery foliage similar to P. argentatus but a
much better growth habit, disease-free foliage and a lot of vigor. We really
never saw much flowering on this species, but it has been a great
humidity-tolerant, gray foliage accent and is still growing strong.

Plectranthus ecklonii
(San Felasco Nursery, Silverhill Seed) are really beginning to bloom as we move
into September. Plants are from 3-4 feet tall and masses of lavender and pink
flowers add another foot to plant height. A Silverwood Seed selection from
South Africa, 'Medleywood' is only budding up now but should be blooming in
another week.

In general, the species we grew from South Africa have not
been commercially acceptable for foliage or flowering, but there is some nice
material there.

Novelty crops

Novelty crops, specialty annuals, component plants, call
them what you will, but this is some of the most interesting plant material
around. It is important to keep track of the commodity crops, but for growers
and retailers, this is the material to fill in profit gaps, personalize your
product mix and create a strong niche. The plants in this category offer a lot
of variety, as well as heat and drought tolerance.

Allamanda schottii -- Dwarf Allamanda style='font-weight:normal'> (Hatchett Creek Farms). Allamanda is known in the
South for its drought tolerance and non-stop summer flowering, but most forms
are gangly and semi-vining. Still blooming in September, these plants have
never gotten more than three feet tall and are covered with bright yellow
4-inch flowers. Great form, but slow starting when conditions are cool.

Bulbine caulescens -- Yellow Bulbine style='font-weight:normal'> (Yucca Do Nursery). A little-known relative of
aloe, this was a really strong performer, with flowers from planting date
through; well; it was still going in September. Needs a hot, sunny, dry
location. This one is larger than the orange, which is also hard to find but very
much worth the effort.

Cleome species -- Linda Armstrong style='font-weight:normal'> (EuroAmerican Propagators). Fantastic color. This
plant was in bloom from liner through late July with pale Á lilac-pink
flowers atop purpleish foliage. Much smaller in stature than seed-produced

Hemigraphis coloratus (Boynton Botanicals). A relative of
the old houseplant called "Waffle Plant," this species is a foliage
color form with purple, burgundy foliage, frosted with silver. It has held up
and grown well in full afternoon sun for the entire season. Much the same
effect and color range as ajuga foliage, but much better in the heat and sun.

Nolana species -- Blue Eyes normal'>(Bodger Botanicals). Not a particularly easy plant to make look good in
a container, but in the field this was a beautiful, petunia-like flower with
striking blue blooms and a very vigorous growth habit. Lasted as well or better
than petunias (finished in week 26), and offered something different in flower
color and foliage texture. Very strong.

Otacanthus caerulus -- Brazilian Snapdragon style='font-weight:normal'> (Bodger Botanicals). Killer, intense sky blue
flowers on an irregularly shaped plant, this was strong and colorful in the
early season; it shuts down in the heat of the Southern summer, but is already
picking up again for a fall flush. Tender perennial in the South, with good
performance. Hey, Jim Barrett likes this plant, and he thinks all component
plants are weeds!

Salvia leucantha 'Santa Barbara' style='font-weight:normal'> (EuroAmerican Propagators). This one received a
relatively low rating but is an excellent plant. The problem is that in Florida
"perennial" salvias flower early and then rest until fall brings
cooler nights. So as I write this, this salvia is in full bloom with lavender
masses of flowers covering a 4 1/2-foot mass of gray foliage. As with all the
perennial salvias, the secret in the South is knowing when their season is so
you can produce them on schedule.

Stemodia tomentosa
(RobRick Nursery). Stemodia is a little-known crop with a lot of potential for
the landscape. Similar to 'Blue Daze' in its gray foliage, this non-flowering
(OK, it does flower, but they are so small and pale, the effect is
non-flowering) accent plant is heat- and drought-tolerant, spreading and pretty
much trouble-free. Also makes a good component plant in mixed containers. Consistent
high evaluations for foliage quality and impact.

Tecoma stans
(RobRick Nursery). Also sold as esperanza or Texas star, this relative of cape
honeysuckle has been in bloom since May, is free-branching, has large clusters
of 3-inch tubular yellow flowers and shows no insect or disease problems. Very
strong, drought-tolerant and easy for growers and landscapers.


This group is still growing, and we will be doing an even
larger production trial in spring 2003. Since calibrachoas have a lot of new
genetics, there is a lot of variability in the group. We ended this trial on
week 30 when it became obvious the plants were not going to re-bloom. Every
entry in the trial had at least two good weeks of high ratings, but only early
in the season.

Million Bells Cherry Pink normal'> (EuroAmerican Propagators) was the top performer this year. This
cultivar just kept blooming longer, repeated stronger and had more color impact
than the rest of the trialed cultivars.

Spring Fling Yellow
(HMA) and
Million Bells Terra Cotta
(EuroAmerican Propagators) were earliest to flower in the field. Peak flowering
was less easily determined, as varieties flushed, then re-bloomed at a later
date. This is part of the reason the Million Bells Cherry Pink stood out so

Milky Blue Calibrachoa
(Twyford Laboratories) is an entirely different form of calibrachoa, with
extremely small leaves and flowers about three-fouths of an inch in diameter.
While this plant was very vigorous, it did not have the color impact of some of
the larger-flowered forms. Still, put on a good display.


We trialed a selection of vegetative-type and seed-produced
(USDA Iowa) varieties and really enjoyed watching this diverse group of plants
perform over the season. Seed types in general had too few flowers for
commercial purposes, but there were some strong plants nonetheless. The
vegetative types clearly outperformed on a season-long basis.

Cuphea ignea
(Hatchett Creek Farms). This form of Cuphea ignea was in bloom at planting and
is still stopping visitors to the gardens. One-inch orange blooms on a 4- to
5-foot plant. Uniform, continuous flowering, very nice.

Some of the more interesting species trialed from USDA that
did well and are in some cases coming back strong in fall include: C. glutinosa,
C. procumbens, C. racemosa, C. schumanii and C. varia.

Vegetative Torenia

I don't think anyone is surprised at the success of this
crop. It is continually in flower, makes a great basket, and even a novice
grower can enjoy success with it. What surprised me was the fact that they also
do extremely well in full sun in the landscape, but they are not
drought-tolerant so keep the water coming for best growth. Every torenia entry
on our gardens has held a perfect 5 rating for most of the season, and they are
still doing great. The blue forms are all excellent, but there was little
commercial difference between them.

Amethyst Wave
(EuroAmerican Propagators, Suntory/Jackson & Perkins). Definitely the most
vigorous of the colors available -- strong, consistent, continuous flowering.
Received the highest ratings of the group. Good size blooms and good foliage

Pink Moon (HMA).
I've been hoping this color would get out and Pink Moon is a good variety.
Extremely large flowers, moderately vigorous. We have a sport of Summer Wave
Blue that we call 'Milton Mauve' that is also in the gardens, but the flowers
are smaller and the growth more vigorous. Hopefully we'll be able to get both
traits into the pink color in the future. A great addition to the crop.


All entries had 2-3 weeks of strong ratings, but their
season of flower is really January or February this far south, so a lot of the
earliest varieties were at peak flower when planted. There is a lot of
variability, but four varieties were still surviving and blooming in the
gardens here in September; they aren't pretty, but they are surviving. The
trial ended on week 26 for most cultivars.

Rainbow Carpet Rose
(Bodger Botanicals). This variety has been in bloom all summer and is still in
bloom. A good semi-upright habit, a strong color that doesn't fade in the heat
and the ability to have powdery mildew but continue flowering. Very strong.

Aztec Pink Magic
(Ball FloraPlant). Another fantastic performer for the early season, this was
hands down the most vigorous verbena in the trial, and peak flowering was a
solid mass of pale pink flowers. Medium-textured foliage, good disease
resistance. This was a very good cultivar.

Tapiens Blue Violet
(EuroAmerican). Also good, long-flowering, but foliage tended to yellow a bit
and flowers faded in the heat. Still, it put on a long and attractive show.

Escapade Red
(Goldsmith Plants). This variety was still flowering heavily in September. The
foliage looked horrible, but the vigor was certainly there.

Napoleon & Sparkler series normal'> (Bodger Botanicals). These honorable mention verbena were so early
that they were past peak flowering by the time we got them into the ground, so
their ratings are very low. They are also unlikely to repeat bloom with any
vigor. So here are some to keep very cool and start very early, not good in a
Southern spring production scenario.

About The Author

Rick Schoellhorn is assistant professor of floriculture at the University of Florida, Gainesville, Fla. He can be reached by phone at (352) 392-1831 or E-mail at

Leave A Comment

  • Web page addresses and e-mail addresses turn into links automatically.
  • Allowed HTML tags: <a> <em> <strong> <cite> <code> <ul> <ol> <li> <dl> <dt> <dd>
  • Lines and paragraphs break automatically.

More information about formatting options

By submitting this form, you accept the Mollom privacy policy.