General Culture:
Winter hardy to USDA Zone 8 (perhaps Zone 7 with protection and mulch) where it is best grown in medium to wet soils in full sun to part shade. Best flowering is in full sun. This is a versatile plant that tolerates an extremely wide range of growing conditions. It thrives as a marginal water plant and in boggy soils, but also does surprisingly well in average garden soils as long as moisture is consistent. Plants tolerate high heat and humidity. New plants may be rooted from stem cuttings. ‘Purple Showers’ will not come true from seed, but will self-seed in the garden, with new plants more closely resembling the species. It should be noted that species plants have naturalized in the southeastern U. S., and are currently listed as a Category I invasive species by the Florida Exotic Pest Plant Council. Invasiveness is clearly not a problem in St. Louis where plants may be grown as annuals, with stem cuttings overwintered indoors if desired.
Noteworthy Characteristics:
‘Purple Showers’ is a vigorous, upright Mexican petunia (also called Mexican blue bell) that typically grows in a clump to 3-4’ tall. Tubular, petunia-like flowers (1.5”) bloom freely from the leaf axils from late spring to frost on greenish-purple stems clad with linear, willowy, sword-shaped, green leaves. Flowers last only one day, but plants often produce an impressive non-stop succession of bloom. Genus name honors Jean de la Ruelle (1474-1537), French herbalist. Due to some unresolved taxonomic and nomenclature issues, confusion currently exists as to the correct specific epithet for this Ruellia. R. brittoniana is currently the most commonly used name in the horticulture trade, but additional candidates for correct name include R. caerulea, R. malacosperma and R. tweediana.
Problems:
No serious insect or disease problems. Plants may spread by self-seeding where it is winter hardy.
Uses:
For USDA Zones 8-10, grow in bog gardens, as pond marginal and in beds and borders. Grow as a flowering annual in the St. Louis area. Excellent free-blooming plant in large containers.
© Missouri Botanical
Garden, 2001-2009
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