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Perennial Profile Blog - Isodon Effusus

10/3/2023 8:26 am



Isodon effusus aka 

Plectranthus effusus (longituba) aka Rabdosia effusus

(Long-Tubed Trumpet Spurflower) 



Quite a few of the delighted guests at Michell Thurmond's Garden Party on September 30, 2023 were intrigued by a bright green leaved perennial growing in part shade that had tight flower buds showing a tip of purple. The plant -- which botanists have changed the name too frequently -- is one of the few dependable fall blooming charmers which is not in the aster family.


Isodon effusus grows in part sun to light shade. Until it begins to flower, the plant maintains a tidy, small shrub-like shape. The flowers are borne along long panicles. As these flowers develop and open, the stems begin to arch from the weight of the multitude of lavender flowers. 


Height-wise, this gem tops out at 3' high with a similar spread, although when it blooms in Fall, the flower panicles can reach a foot or two further in all directions.  Depending on where you plant it, this arching bloom form can produce a pleasant interweaving effect with plants whose bloom time has passed or plants with blooms that blend well with lavender.


Isodon effusus is hardy in Zones 6a-8b. If the plant blooms before the hummingbirds head south, you will definitely see them feeding on the small purplish tubular flowers. Bees are very fond of it too. This plant is a gentle self sower close to the mother plant, so once planted you should have a supply to move around and share.


It's a favorite of Dr. Armitage, which is reason enough for anyone to try it! I concur and have been growing it since 2016. Even when not in bloom, the light to medium green foliage is very vibrant and noticeably attractive.


Currently known sources for the plant with too many names include Plant Delights and Far Reaches Farm. However, checking in with a garden friend who has this plant and might part with some bonus babies is also a good option.


Contributed by Liane Schleifer