Osteospermum Cultivar Trial 2004
In 2004, we conducted osteosper-mum/African daisy trials in our departmental greenhouses on the Columbus campus for the seventh consecutive year. We evaluated 26 entries from four source companies in the trial period from January through early May. Rooted cuttings were received from participating companies between January 2 and 16.
During the week of January 8-16, we rooted cuttings of 20 plants per cultivar, with the exception of two experimentals from Proven Á Winners. Liners were then transplanted into 41?2-inch pots. Our potting media was MetroMix 360, and the greenhouse temperature remained at 72° F day/night. On February 12, we pinched plants to 5-6 nodes. Cold vernalization initiated on February 26 with day/night temperatures of 46° F. On April 8, cold temperatures ended, and warm temperatures of 65° F days and 55° F nights were maintained through the end of the trial. On April 19 cultivars with no vernalization requirement (or minimal vernalization needs) were at peak flower. During the weeks of April 27 through May 2, a majority of cultivars were at peak flower (vernalization-requiring cultivars).
For fertilization, we used Greencare 17-5-17 at 200 ppm nitrogen, three times per week. Two disease problems arose during the trial. Pythium root rot was detected on some plants in late January. Plants were then drenched with Plant Shield (BioWorks) at the maximum rate on January 28 as a preventative measure for further problems. In mid-April, Botrytis was detected, and treatment with Heritage (Syngenta) took place on April 23. For this cultivar evaluation, no growth regulators were used. This provided a good indicator of the natural growth habit of each cultivar.
Four evaluations, using specific criteria, were made to judge the performance of each plant. The first was plant height to top of flowers (see Figure 3, left), which was measured on May 3.
During the second evaluation, the main cultivar evaluation (see Figure 1, page 66) was performed by the trials leader and trials coordinator. This evaluation was taken on April 29, when the majority of cultivars were at peak flowering.
Evaluation criteria ratings were based on a scale of 1-5: 1 = poor/not acceptable, 2 = fair, 3 = good, 4 = very good and 5 = excellent. Plants were evaluated for the following characteristics:
- flower number;
- flower quality: flower aesthetics, color, health and appearance;
- vegetative/foliage quality: plant habit, plant vigor, leaf color, health and appearance of vegetative portion of plants; and
- overall: overall rating for all plants in the grouping, taking the above aspects into consideration.
The consumer preference evaluation (see Figure 2, left) was the third evaluation. It was performed by our annuals team of Master Gardeners on April 22-27. Plants were given an overall rating of 1-5 based on personal preference.
In the fourth evaluation — flowering before cold vernalization, seen in Figure 4, right — we recorded the number of plants with flower buds and open flowers on February 2, just two weeks after transplant. The open flowers were subsequently removed. All plants in the trial were pinched 10 days later on February 12 according to the cultural schedule guidelines. The data presented in Figure 4 reflects those entries that require minimal or no vernalization treatment; however, all entries did receive the six-week prescribed vernalization period.
The top entries, those with an overall ranking of above 4.0, in the cultivar evaluation as rated by the trials leader and trials coordinator at the time of peak flower were: ‘Pinwheel Purple’, ‘Symphony Lemon’, ‘Symphony Vanilla’ and ‘Symphony Orange’. Also performing well, and all tied with a ranking of 4.0, were IN47, ‘Pinwheel White Eye’, ‘Seaside’, Exp. V77-9B-3C, ‘Symphony Cream’, ‘Iringa’ and ‘Margarita Maria’.
The top five entries (with an overall ranking of above 4.0) in the consumer evaluation were ‘Soprano Purple’, ‘Nairobi Improved’, ‘Symphony Orange’, ‘Symphony Lemon’ and ‘Iringa’. Also performing well, with a rating of 4.0, was ‘Seaside’ and Exp. V77-9B-3C. Note that both ‘Symphony Lemon’ and ‘Symphony Orange’ were top finishers in both evaluations.
Each year, we receive an increasing number of entries with little or no cold vernalization requirement. This year, the following entries had plants in bud and/or with open flower on February 2, just two weeks after transplant and 10 days before plants were pinched. At the end of the trial, these entries were all at peak bloom two weeks sooner than vernalization-requiring cultivars. Soprano series (three cultivars — White, Light Purple and Purple), Symphony series (five cultivars — Cream, Lemon, Orange, Peach and Vanilla) and experimentals IN46 and IN47.
Since no growth regulators are used in this trial, it is always interesting to observe natural plant heights. Final plant heights almost doubled from the shortest entry, ‘Cape Daisy Nasinga Cream’ (71?2 inches) to ‘Margarita Rosita’ (14 inches). Entries all finishing off below 8 inches were ‘Cape Daisy Nasinga Cream’, ‘Pinwheel White Eye’, ‘Pinwheel Purple’ and ‘Margarita Maria’.