Trialing Diascia and Nemesia By Rick Schoellhorn

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

The University of Florida evaluations generate informationon Southern landscape performance but also information on cold tolerance andphotoperiodic responses of these crops, which are used as spring annuals in theNorth. A cultivar that does well during the University of Florida winter trialswill 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 maynot flower on schedule or if minimally heated greenhouses are being used. Thetrial was conducted online with both pictures of the plants every two weeks,and ratings sheets are available on the Internet at:

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


Before discussing the results of the trials, I’d like to goover 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 weeksthroughout the season. The horizontal axis is the weeks of 2002-2003 when weheld the trial. So as you look at the graphs for the different cultivars, theamount of weeks their ratings are above a 3 indicates their overall performanceduring the trial. The peaks and valleys in the graph indicate high points inflowering and low points in performance. The low point in mid trial is theresult of the season’s coldest weather with eight nights of temperatures below25° F. The final point (in red) at the right of the graph is the averagerating for that cultivar over the entire season; all other points indicate performanceat that date within the trial.

Some basic, overall notes on the performance of diascia andnemesia in this trial: Both crops were temperature sensitive in theirperformance, with highest ratings occurring under warmer temperatures. It isreally interesting to look at these graphs and see what early cold performancewas and then compare it to late trial performance when temperatures were risingwith Florida’s “spring” conditions. Freezing temperatures knockedflowers of both genera, but cultivars with higher ratings were those thatregenerated flowers the quickest, so the plants which did not abort buds atcold temperatures bounced back to higher ratings faster. Some plants remainednearly dormant during early trials, which gives them a flat rating. Others grewand flowered even under early winter conditions.

Both nemesia and diascia flower in cycles, which means youget blooms in flushes. Higher ratings went to cultivars with the shortestperiod of time between these “peak blooms”.

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


Diascia were more cold hardy and quicker to establish asolid mass in the trials than nemesia, making their average ratings somewhathigher. Highly rated cultivars did not burn or yellow under freezingconditions, grew enough to form a canopy between individual Á plants,and flowered either over a longer season or with consistently better floweringthan cultivars with lower ratings. All diascia cultivars survived the winterand continued in the gardens as part of the spring trials. We were hoping tosee how the plants continued to perform under spring and into summer conditionsin 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 agreat, strong orange-salmon color, consistent growth and performance, and goodfoliage color and cold tolerance.

‘Whisper Salmon Red Improved’ from Ball FloraPlant has anaverage rating of 3.6, peak bloom from week 11-13, and excellent early seasonperformance. Incredibly vigorous growth and strong red-toned flowering that areless of a true salmon; flowers held on longer stalks for a lighter appearancebut good mounding growth habit and foliage color; and excellent cold tolerance.

‘Whisper Cranberry’ from Ball FloraPlant has an averagerating 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 subtlydifferent, crisper red coloring and excellent foliage and habit.

Honorable mention.’Wink Pink’ from Ball FloraPlant with an average rating of 3.3 and ‘FlyingColors Antique Rose’ from Proven Winners with an average rating of 3.2.


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

In general, white cultivars performed the best, though blueand pink cultivars also scored highly. There were two very nice numberedentries from The Flower Fields that exhibited bicolor flowers or new colorforms, but both of these hit their peak bloom much earlier in the season thanother entries and then died almost immediately after flowering. I think theyare worthy of note for their color breakthroughs and also for the coldtolerance both cultivars exhibited in the early half of the trials. Bothentries bloomed earlier and re-bloomed faster after freezing than otherentries, their demise was when temperatures rose in the later half of thetrial.

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

‘Aromatica White’ from Ball FloraPlant had an average ratingof 3.3 with peak bloom weeks 7-15. It is a larger plant and more vigorous thanCompact Innocence. It made for a more impressive display of color, but also ledto some lodging as the season went on.

‘Safari Pink’ from Proven Winners had an average rating of3.2, peak bloom weeks 9-15, large vigorous plants really came on strong whenthe weather warmed. Safari Pink had a great clear pink color, larger moundinggrowth 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 withnemesia, there were a lot of very good blooming plants that were rated low forthe trial. In most production situations, freeze tolerance will hopefully neverbe an issue; however, for growers looking to start early in spring or get alonger fall season, this cold-tolerance information will be very helpful.

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

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

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Rick Schoellhorn

Rick Schoellhorn is extension specialist at the University of Florida, Gainesville, Fla. He can be reached by phone at (352) 392-1831 x364 or E-mail at [email protected]

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