Trialing Diascia and Nemesia

The following report of diascia and nemesia trials conducted at the University of Florida trial gardens in Gainesville, Fla., was conducted in the winter of 2002. Gainesville is in USDA Zone 8b and is part of an ongoing research program to evaluate new crops for their potential as winter flowering crops. While Southern and Sunbelt producers can use this information to boost winter sales and extend fall-season sales, Northern growers might wonder how this type of trailing affects their use of product, and the answer is two-fold.

The University of Florida evaluations generate information on Southern landscape performance but also information on cold tolerance and photoperiodic responses of these crops, which are used as spring annuals in the North. A cultivar that does well during the University of Florida winter trials will likely also make for a good bet in early spring production in the North, offering Northern growers some options for early production when many crops may not flower on schedule or if minimally heated greenhouses are being used. The trial was conducted online with both pictures of the plants every two weeks, and ratings sheets are available on the Internet at: http://hort.ifas.ufl.edu/floriculture/wintertrials2002/index.htm.

The plant ratings were those taken every two weeks, so average ratings will be lower as these plants flower; cyclically they cannot always be a perfect five. The ratings are 0 = plant is dead; 1 = plant is growing poorly with little vigorous growth and little or no flowering; 2 = plant is growing and flowering, but not performing well enough to merit use; 3 = plant is growing and flowering enough to be considered of use in winter production; a rating of 3 is the cutoff point for acceptable performance; 4 = good growth and flowering with enough impact to be considered a strong candidate; and 5 = plant is at peak performance with exceptional flowering and vigorous growth. When averaged over the entire season, any average rating much below a 2.5 means the plant did not have a long enough season to be of use in winter plantings under winter conditions similar to those experienced in 2002.

Graphs

Before discussing the results of the trials, I'd like to go over the graphs that begin on the right, presented for the different cultivars. The vertical portion of the graph is the quality rating taken every two weeks throughout the season. The horizontal axis is the weeks of 2002-2003 when we held the trial. So as you look at the graphs for the different cultivars, the amount of weeks their ratings are above a 3 indicates their overall performance during the trial. The peaks and valleys in the graph indicate high points in flowering and low points in performance. The low point in mid trial is the result of the season's coldest weather with eight nights of temperatures below 25° F. The final point (in red) at the right of the graph is the average rating for that cultivar over the entire season; all other points indicate performance at that date within the trial.

Some basic, overall notes on the performance of diascia and nemesia in this trial: Both crops were temperature sensitive in their performance, with highest ratings occurring under warmer temperatures. It is really interesting to look at these graphs and see what early cold performance was and then compare it to late trial performance when temperatures were rising with Florida's "spring" conditions. Freezing temperatures knocked flowers of both genera, but cultivars with higher ratings were those that regenerated flowers the quickest, so the plants which did not abort buds at cold temperatures bounced back to higher ratings faster. Some plants remained nearly dormant during early trials, which gives them a flat rating. Others grew and flowered even under early winter conditions.

Both nemesia and diascia flower in cycles, which means you get blooms in flushes. Higher ratings went to cultivars with the shortest period of time between these "peak blooms".

In general, response to cold temperatures was seen in the form of bud abortion, flower drop, leaf yellowing, leaf purpling and time of recovery. Response to warmer temperatures included increased growth and flowering, and also, for some nemesia, peak bloom and death. Almost all cultivars reached a rating of 4 at some point in the trial, but the key is how long do they hold those higher ratings? A plant with a longer bloom cycle also has a longer sales window and, most likely, a better consumer rating when it reaches the consumer. A final note on liner quality, entries which came in late, small or with shipping damage definitely suffered in the trial, as they did not perform well in early season and so have lower average ratings.

Diascia

Diascia were more cold hardy and quicker to establish a solid mass in the trials than nemesia, making their average ratings somewhat higher. Highly rated cultivars did not burn or yellow under freezing conditions, grew enough to form a canopy between individual Á plants, and flowered either over a longer season or with consistently better flowering than cultivars with lower ratings. All diascia cultivars survived the winter and continued in the gardens as part of the spring trials. We were hoping to see how the plants continued to perform under spring and into summer conditions in Florida.

Best of Class. 'Flying Colors Coral' diascia from Proven Winners had an average rating of 3.6, peak bloom from week 9-15, and acceptable early season performance. It has a great, strong orange-salmon color, consistent growth and performance, and good foliage color and cold tolerance.

'Whisper Salmon Red Improved' from Ball FloraPlant has an average rating of 3.6, peak bloom from week 11-13, and excellent early season performance. Incredibly vigorous growth and strong red-toned flowering that are less of a true salmon; flowers held on longer stalks for a lighter appearance but good mounding growth habit and foliage color; and excellent cold tolerance.

'Whisper Cranberry' from Ball FloraPlant has an average rating of 3.6, peak bloom week 7-15 and excellent early season performance. Cranberry has the same great vigor as Salmon Red Improved with a subtly different, crisper red coloring and excellent foliage and habit.

Honorable mention. 'Wink Pink' from Ball FloraPlant with an average rating of 3.3 and 'Flying Colors Antique Rose' from Proven Winners with an average rating of 3.2.

Nemesia

Nemesia suffered under early winter conditions and intense cold. As a result, most of their early season ratings were low, and all cultivars performed better in the latter half of the trial. This indicates that their potential for winter use under temperatures similar to those in Gainesville this year would be limited. Also, flowering was much more affected by freezing temperatures, and bud abortion was more common in nemesia than in diascia. Highly rated cultivars did not die, burn or yellow under freezing conditions, had good green growth and maximized flowering weeks 7-15 for 2003. Not all cultivars had 100-percent survival in the cold, which lowered their overall rating. 

In general, white cultivars performed the best, though blue and pink cultivars also scored highly. There were two very nice numbered entries from The Flower Fields that exhibited bicolor flowers or new color forms, but both of these hit their peak bloom much earlier in the season than other entries and then died almost immediately after flowering. I think they are worthy of note for their color breakthroughs and also for the cold tolerance both cultivars exhibited in the early half of the trials. Both entries bloomed earlier and re-bloomed faster after freezing than other entries, their demise was when temperatures rose in the later half of the trial.

Best of Class. 'Compact Inno-cence' from Proven Winners had an average rating of 3.0, peak bloom weeks 7-15, great compact habit, some yellowing under early conditions, but extremely uniformity and quick re-bloom after cold or recycle into flower between peak blooms. White blooms covered plants with little lodging and long-lasting color.

'Aromatica White' from Ball FloraPlant had an average rating of 3.3 with peak bloom weeks 7-15. It is a larger plant and more vigorous than Compact Innocence. It made for a more impressive display of color, but also led to some lodging as the season went on. 

'Safari Pink' from Proven Winners had an average rating of 3.2, peak bloom weeks 9-15, large vigorous plants really came on strong when the weather warmed. Safari Pink had a great clear pink color, larger mounding growth habit and was very impressive in late season.

Honorable Mention. 'Blue Bird' from Proven Winners had an average rating of 2.9.

Because of higher mortality under freezing temperatures with nemesia, there were a lot of very good blooming plants that were rated low for the trial. In most production situations, freeze tolerance will hopefully never be an issue; however, for growers looking to start early in spring or get a longer fall season, this cold-tolerance information will be very helpful.

Also, note where ratings are higher in both the early and later portions of the trial; it indicates a free flowering nature in the plant, so a good candidate for early spring plantings where photoperiod may be shorter.

In 2003, winter trials will include verbena, calibrachoa, trailing petunias, dianthus and other focus crops, and all trials will in the Web-based format of the 2002 winter trials. You can find these trials at www.hort.ifas.ufl.edu as well as spring trials for 2002 and 2003.