January 15, 2015
Poor summer provides great conditions at Trial Garden
Cardoon (Cynara cardunculus) was the show stopper in the trial gardens in 2014.
By Rodger Tschanz

Last summer was the summer that barely happened, or so it seemed to the many of us growing warm season plants in our gardens.  

If there was a plus side for a trial garden manager, it was that the climate last summer provided excellent conditions for testing the disease tolerance of the trial plants. Diseases such as botrytis speck on petunias and white mold on vinca and osteospermum flourished last year; cultivars that withstood that onslaught were exceptional.

This review of good performers in the garden trials will focus on those plants that did well despite difficult growing conditions of 2014.

Shade plants

As plant suppliers try to offer consumers shade garden alternatives for impatiens, the number of shade plants in the trials has increased, accordingly.  

Begonias are one plant group that can offer lots of variety of form and colour for the shade garden. Long the purview of the interior landscape and rarely planted outdoors, the Rex begonia has become more commonly available for the home gardener. The Jurassic series of Rex begonia was trialed with fair to good results, depending upon the individual colour in the series. Jurassic Green Streak, Jurassic Silver Point and Jurassic Pink Shades showed vigorous growth throughout the season, while Jurassic Watermelon was the least vigorous of the series and even appeared stunted under certain growing conditions. Based on our trials in 2014, this begonia series grew better in the soilless mix of containers, than in the mineral soil of beds.

Although the Rex begonia does bloom late in the season, the ornamental value of this plant lies chiefly in its colourful foliage. For bloom options in the begonia, we evaluated a number of wax begonias cultivars, as well as the relatively new group of Begonia boliviensis.

The wax begonia is known to tolerate both full sun and shade conditions. The ‘Big’ series with red and pink flowers and both green and bronze coloured foliage options was a great addition to the landscape. Although not new to the industry, this series was grown again in 2014 to help promote its use in the landscape. Its vigorous growth in both containers and beds make it a great choice for large areas. The flowers stood up very well to pounding rain and cool fall weather. This begonia hybrid gets its name because of its tall growth habit and large leaves.

The Santa Cruz Sunset begonia is a selection of B. boliviensis with orange flowers and small angel wing shaped leaves. This was trialed in both sun and shade and in ground beds and containers and was an excellent performer in all conditions. This plant has a semi-trailing habit that lends itself well to use in containers, as well as ground beds.

The New Guinea impatiens (NGI) is also seen as an alternative flower for shade gardens. Twice as many NGI and hybrids were trialed this year over previous years. Vigourous cultivars such as Sunpatiens, Big Bounce, and Super Sonic are some of the best for filling in shady garden areas. More seed-propagated NGI cultivars are in the marketplace now; check out the new colours available in the Florific and Divine series.

More petunia options for 2015

Petunias in general had a lot of disease pressure this past year with botrytis speck appearing on many trial entry blooms. This disease appeared as small whitish specks on the bloom, taking away from the overall bloom colour. One cultivar that has exceptional resistance to the disease, as well as pounding rain, was Whispers Star Rose. This cultivar has a trailing habit and a small flower with a pink star pattern on the petals.  

Another small-flowered cultivar with petunia characteristics is the series SuperCal. Although petunia-like in appearance, this series is actually a type of Petchoa, a cross between petunia and the calibrachoa. It has favourable characteristics of both genera. The foliage isn’t sticky, as is often the case with petunia foliage. It grows well in flowerbeds and containers, and has very good disease tolerance.

What is it about a blue petunia that attracts the attention of visitors to the trial gardens? In 2013, FlashMob Bluerific was a favourite and in 2014 it was Happytoonia Blue. In addition to having a catchy cultivar name, Happytoonia Blue grew very well in the beds and containers, despite the weather.

Some unusual plants for the garden

Cuphea is a relatively uncommon ornamental for the garden. It is easy to grow, and once established requires little maintenance. This is one genus that we haven’t tested for many years. Suddenly in 2014 we tested three cultivars. One of these cultivars, Cuphea Vermillionaire, is commonly called a firecracker plant. It’s a name that describes its small, but long, cylindrical-shaped flower that is coloured in shades of orange, yellow and red. This plant works well as filler in mixed containers and in the landscape, where conditions are hot and dry.  

The Sriracha series of the species Cuphea llavea was also trialed in 2014. In the culinary world, sriracha is a type of Southeast Asian hot sauce, while in the gardening world Sriracha is colourful, compact, and a low maintenance plant for hot, dry conditions. Unlike Vermillionaire, the Sriracha flowers are more pinwheeled in form and available in pink, rose and violet colours. This series proved very attractive to a wide range of pollinators.

In ending this article, I would like to mention a plant that was, by chance, planted into the trial garden simply to create some height in the centre of a large trial bed at the Landscape Ontario office.  

Cardoon (Cynara cardunculus) is an old fashioned Victorian vegetable that is related to the artichoke. It has large, thistle-like grey/green leaves and by the end of the growing season can be quite large; some of the plants in the trial garden reached diameters of almost two metres. I have noticed this plant is used by many municipalities in beds, where visual impact is needed; the same could be done for those landscape clients looking for something different.  Availability of finished plants may be a limitation to its use, but the fact that cardoons are easy to grow from seed may help to overcome availability issues.

The following companies helped to make the Trial Gardens a success:

Plant breeders and distributors
American Takii, AmeriSeed, Ball Horticulture, Benary, Blooms of Bressingham, Danziger, Dummen Group, Florist Holland, Floranova, Fred C. Gloeckner & Co., Goldsmith Seeds, GreenFuse Botanicals, Jelitto Seeds, Kieft Seed, PAC, Pan American Seed, Pro-Veg Seeds, Proven Winners, New Mexico State University, Sakata Seeds, Selecta North America, Syngenta, Vanhof and Blokker, and William Dam Seeds.

Growers and suppliers
Everris, Linwell Gardens, Plant Products, George Sant Greenhouses, Ed Sobkowich Greenhouses, Gro-Bark, JVK (Jack Van Klaveren Ltd.), MCP Manufacturing, Myers Industries Lawn and Garden Group, SunGro Horticulture, Windmill Landscapes.

Other organizations
All-America Selections, Association of Specialty Cutflower Growers, Guelph and Wellington County Master Gardeners, City of Guelph - Healthy Landscape Program, Ontario Ministry of Agriculture and Food, Vineland Research and Innovation Centre, Landscape Ontario and the Department of Plant Agriculture at the University of Guelph.
Rodger Tschanz, University of Guelph, manages the Trial Gardens at Landscape Ontario home office in Milton.