My husband assigned to me the responsibility of watering all the plants in our home garden. This was no light task, since we always had more plants in pots than we had plants in the ground, and in the heat of summer, many of the potted plants had to be watered at least once, if not twice, every day. I usually kept up on the watering (or told him that I had). But there was one gangly odd-ball plant that kept getting pushed to the back and frankly, it often got watered only when I noticed that it was wilting (rather badly). It had a name I didn’t recognize — Rabdosia longituba — and an overall appearance that was, well, nothing remarkable.
Needless to say, as a dutiful spouse I tried to remember to keep the plant watered. When it still hadn’t flowered by the end of the summer last year, I started to think the plant had it in for me. Maybe it wouldn’t flower at all, since I’d neglected it so? By our anniversary the end of September, I became convinced that it was only by sheer luck that I wasn’t divorced over the plant’s failure to bloom. There it sat, rather pathetic, a mound of green leaves that were, thankfully, still not totally crisp from lack of moisture.
Then one day in October, I noticed a large spray of simply beautiful blue flowers in the potted plant area on the driveway. Had he brought home yet another potted plant for me to water when I wasn’t looking? No. It was the Rabdosia longituba, also called trumpet spurflower. The flowers, held on tall stems that rose at least a foot above the plant, were a pale blue-purple, each one shaped like a little trumpet. The overall effect was open and airy, a wonderful filler flower for bold splashes of orange and yellow in the autumn border.
Rabdosia longituba is a member of the salvia family (in a previous botanical life, it was called Plectranthus longitubus). Growing wild along the edge of woodlands in Japan, it is best suited for part sun or light shade. Gene Bush and JoAn Riley of Munchkin Nursery in DePauw, Ind., reports that it is very sensitive to frost, so if you’ve got an early cold spell coming on when it’s about to flower in late fall, make sure to give it overnight cover. Munchkin also suggests that the plant be pruned back in July to force side branching, so that the tall wands of flowers don’t flop over.
Trumpet spurflower is hardy in Zones 6 to 8. There is a cultivar called ‘Momokaze’ with pink flowers and another called ‘Tube Socks’ with white flowers. The latter was found, introduced and named by Barry Yinger.
Common Name: Trumpet spurflower
Botanical Name: Rabdosia longituba
Color: Purple-blue flowers on tall stems with green foliage
Size: Grows about 36 inches tall in a clump 24 inches wide
Exposure: Part sun to light shade
When to Plant: Spring to fall
How to Plant: Crown at soil depth
Soil: Regular garden soil
Watering: Moist, well-drained soil
When to Prune: Trim back spent foliage and deadhead after flowering
When to Fertilize: Standard fertilizer once a month during summer
In Your Landscape: Ideal for part shade in the fall border or woodland garden, or in an autumn container in light shade
(From Indiana Gardening Magazine Volume I Issue V. Photos courtesy of Sue Speichert.)