SASKATCHEWAN PERENNIAL SOCIETY

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	But is it Hardy on the Prairies?

	As in other regions, perennials have become increasingly popular in prairie gardens. 
	Historically, the biggest question has been that of winter hardiness. Most of this area is
        located in zones 2-3, while most hardiness research is conducted in zones 4-5.

	Thanks to a recent study funded by the Perennial Plant Association and coordinated
        through the Saskatchewan Perennial Society, we now know a little more about Aster, 
	Geranium and Dianthus.

	All of these do well in full sun and are moderately drought-tolerant - qualities
        appreciated by prairie gardeners where sunny days are abundant but natural precipitation
        is often limited.

	Dianthus have both flower and foliage appeal and are widely used in herbaceous borders
        and rock gardens. Geraniums are finding homes in borders, rock gardens and as ground 
	covers. Aster extend our season into the fall if they bloom by September. Different 
	heights and colours give them a range of landscape uses, but many are susceptible to 
	powdery mildew.

	Testing sites across the prairies covered an area about 1000 kilometers east-west by 300 
	kilometers north-south, with varying soils in zones 2-3.  All were in publicly accessible 
	gardens: the Skinner Arboretum Trail, Roblin, MB (zone 3a); the Forestry Farm Park, 
	Saskatoon, SK (Zone 2b); the Calgary Zoo Gardens, Calgary, AB ( 3b - Chinook area); 
	and the Crop Diversification Centre South, Brooks, AB (zone 3 - Chinook area).

	As Erl Svendsen, project manager of the trials for the SPS, noted: "Site characteristics, 
	especially micro-climate, can play a large role in plant survival.  When testing across a 
	large region, this factor is nearly impossible to eliminate or account for.  This is 
	especially true for small trials that are evaluated for a short period."

	Still, there were a few clear winners and losers. Showing consistent winter survival were 
	Dianthus alpinus (mixed), 'Little Boy Blue' and 'Spring Beauty'; Geranium 'Biokovo', 
	'Ingwersen's Variety', 'Johnson's Blue', 'Max Frei' and 'Mrs. Kendall Clark'; and Aster 
	'Alert', 'Little Pink Beauty' and 'Purple Dome'. Poor survival rates were found with 
	Dianthus 'Doris', 'Frosty Fire', and 'Spotty', and Geranium 'Silver Shadow'. 

	Plants that performed inconsistently across the sites were Dianthus albus, 'Tiny Rubies' 
	and 'Zing Rose'; Geranium 'Biokovo', 'Mayflower', 'Patricia', 'Splish Splash' 
	and 'Wargrave Pink'; and Aster 'Alma Potshke' and 'Professor Anton von Kippenberg'

	Olivia Johns, horticulturist at the Calgary Zoo, found 'Patricia' geranium to be a prolific 
	producer of unattractive seedlings with small white blooms that quickly became a weed 
	problem while the original plants failed to over-winter. 'Patricia' is not recommended.

	Only Aster 'Purple Dome' escaped mildew infection.  Asters in Calgary (western-most 
	site) flowered earlier (August - October, depending on the cultivar) than those in Roblin 
	(eastern-most site) where buds did not show colour until mid-October.


			-prepared by Sara Williams