February 15, 2009
By Rodger Tschanz
University of Guelph Trial Garden manager

The summer of 2008 saw the expansion of the trialing relationship between the University of Guelph and Landscape Ontario. Over 6,000 square feet of trialing space at the Landscape Ontario site in Milton was planted with annuals and perennials for evaluation of their potential in the landscape. These same plants were also trialed at the University of Guelph Trial Gardens. Growing the plants in two locations allows testing under two different sets of growing and cultural conditions, giving a much better picture of how these plants perform in southern Ontario.

Visitors to the gardens were asked to vote on their favourites. Top results from the voting by horticulturists at the open house days in August 20 and 21, 2008 were as follows:
1) Rudbeckia ‘TigerEye Gold’
2) Zinnia ‘Zahara Scarlet’
3) Lantana ‘Landmark Sunrise Rose’
4) Sedum ‘Angelina’
5) Zinnia ‘Magellan’ series

1) Rudbeckia ‘TigerEye Gold’ generated a lot of interest in every trial I attended in 2008. This F1 hybrid is propagated by seed and has very consistent growth habit, giving an even and predictable look to a mass landscape planting. In the combined LO/Guelph Trials, we planted out relatively small plants (i.e. the equivalent of an 806 garden pack) in mid-June and had a full bloom presentation by mid-July. The plants bloomed non-stop and were abundant until frost damaged the flowerbuds in early October. Our observations this year suggest that this rudbeckia is resistant to powdery mildew. The literature suggests that ‘TigerEye Gold’ should be treated as an annual. We left the plants in the trial beds for the 2008/2009 winter to observe this for ourselves. Until you hear differently, it can’t be assumed they are winter hardy. When using small plants (as we did this year) in the landscape, try planting with spacing of eight inches for fast fill-in. With larger plants (i.e., four inches) you can space at 12 inches. This plant will spread to at least 16 inches during the growing season and reached heights (in full sun) of approximately 18 inches. Consider planting in combination with a purple spike-like plant such as Salvia ‘Mystic Spires Blue’; the gold and purple complement each other very well.

2) The two zinnia series that were the most popular in 2008 were ‘Magellan’ and ‘Zahara.’ The petals stood up well to the exceptional rainfall we experienced last summer. Both of these series tolerated disease pressure well into September. The ‘Zahara’ zinnias are selections of the Zinnia marylandica and closely resemble ‘Profusion’ zinnias, in terms of flower form (daisy-like), size and disease resistance. The garden height and spread of the ‘Zahara’ series is 12 to 18 inches; plant spacing of 10 to 12 inches is adequate for a fast fill-in. Scarlet seemed the most popular colour chosen by visitors to the garden, but ‘Zahara’ cultivars of white, coral rose and yellow are also available.

The ‘Magellan’ zinnias are selections of Zinnia elegans and display the large and showy flowers of the “traditional” zinnia. ‘Magellan’ is available in eight colours that range from ivory to yellow and to orange to cherry; all plants within the series had a similar growth habit and bloom performance and the favourites chosen by visitors depended upon individual colour preferences. The garden height of this cultivar is 12 to14 inches; a spacing of eight to ten inches for 806 sized plants is adequate to achieve a quick canopy fill-in.

3) The 2008 Guelph trial had ten lantana entries. This tropical shrub is used as an annual in landscape beds and containers. Some cultivars are trained to form standards to provide some height to a container or bed. Lantana is very tolerant of heat and its colours range from white to yellow to orange to purple. Many lantana cultivars have flower clusters that change colour as the individual flowers age. In the case of this year’s favourite, ‘Landmark Sunrise Rose,’ the florets open yellow and then turn orange and pink as they age. The lantana bloomed constantly throughout the summer up until frost. The lantana in the 2008 trials varied in vigour and grew to heights of anywhere from 15 to 20 inches. Although the flowers of ‘Sunrise Rose’ were extremely showy, it was the least vigorous of the ‘Landmark’ series. The plants for the 2008 trial were grown in four inch pots and planted out at a spacing of 12 inches. ‘Sunrise Rose’ should have been spaced at ten inches to fill in faster than it did.

4) New for the 2008 trials was a selection of sedums that were planted out in the non-irrigated trial bed. This year turned out to be a poor one to test drought tolerance of landscape plants. As consequence, it resulted in testing the rain tolerance of some species of succulents. One that stood out as exceptional for the visitors to the trial garden was ‘Angelina,’ a selection of the species Sedum rupestre. During the warm part of the summer, this plant, with its small needle-like foliage, was yellow-green in colour. As fall temperatures arrived, the foliage turned a brilliant yellow-orange. According to the literature, ‘Angelina’ should be hardy to USDA Zone 3. The plants for this trial were propagated in the greenhouse and finished in four inch pots. They were planted in the garden with 12-inch spacing. This spacing was a little too generous to allow for a quick, first season canopy fill-in; six to eight inches would have been better. Overall height of the plant in the trials was three to six inches.
For more information about these cultivars and the landscape trials go to www.plant.uoguelph.ca/trialgarden, or contact Rodger Tschanz at 519-824-4120, ext. 52788, or by email at rtschanz@uoguelph.ca