Rose-Allamanda, Climbing Oleander

Strophanthus gratus (Wallich. & Hook.) Baillon

stro-FAN-thus GRAT-tus

Apocynaceae

Explanation of name: The name Strophanthus is derived from the Greek strophos (a twisted cord or rope) and anthos (a flower), thus expressing the chief peculiarity of its appearance, the limb of the corolla being divided into five, long, tail-like segments. http://www.botanical.com/

botanical/mgmh/s/stroph96.html.  Gratus means grateful.

Natural range: Africa

Recognition:  Large-leaved twining vine with milky sap and round, showy, fragrant  rose-colored (or white) blossoms 2" in diameter. Petals 5, with fingerlike projections extending from the flower center.

Landscape uses:  Novelty. Large, aggressive, showy flowering vine in need of support.  

Internet sources:

http://www.desert-tropicals.com/Plants/Apocynaceae/Strophanthus_gratus.html

http://www.rareflora.com/strophantusgra.htm

Garden Guru artivcle on Rose Allamanda, Palm Beach Post, by George Rogers:

Although a double misnomer---not a Rose and not an Allamanda---the Rose-Allamanda is splendid now in late winter showing off its flowery glory. Surprisingly, this species is unfamiliar to many gardeners despite being a serious head-turner.  Driving along, your eye might catch a plant so blanketed in large rosy blossoms you can't see the leaves. What the heck was THAT!?  Turn around, go back and scope it out, it's Rose-Allamanda.  Nothing else looks like it.

The variable flowers combine white, lavender, and burgundy.  The fragrance resembles a rose, so perhaps the vine's name refers to the floral aroma and not to the flower color, or then again, perhaps the namer had both looks and smell in mind.  The flowers have a distinctive crinkly crown (properly called a corona) jutting from the dark centers. Think of a hand in a cup with the fingers jutting out. The large glossy leaves are in pairs and drip milky sap if broken.  The double fruits can be 15 inches long, filled with hundreds of small seeds having fluffy parachutes.  Some closely related species have escaped cultivation by means of such wind-borne seeds, but I am not aware of this problem with today's species.

Rose-Allamanda belongs to the Dogbane Family along with Allamanda, Carissa, Desert-Rose, Frangipani, Mandeville, Oleander, Rosy Periwinkle, and many other landscaping favorites generally inclined toward dry conditions.  Today's species leans the opposite way, preferring consistently moist soil, this well drained and enriched organically. Full sun or partial shade are requirements.  Cold weather is trouble. The rambunctious vines fill in thickly and extend over 20 feet long, needing a strong trellis or pergola.  Cuttings or seeds allow easy propagation.

Be careful, this plant resembles its relative Oleander by containing powerful heart toxins.  Rose- Allamanda is one of the few botanical sources of the drug ouabain (WAW-bane), which is a naturally occurring human hormone involved in regulating heart function.  The toxin has a long history as an African arrow poison and in traditional medicine, this leading to a modern role in cardiology, mostly in Europe and in research.  This is not a plant to enjoy where children or pets might nibble.  Also on the downside, remember that the flowering is seasonal; the rest of the year there's just a glossy green vine.

This species is a temporary highlight to be used carefully and sparingly as a novelty, as a splash of color, as one hit in the annual hit parade.  The various drawbacks as just described limit its uses, yet a gardener who can provide a sunny site, a supportive structure, rich constantly moist soil, and assurance of no danger to creatures and kids can have some fun with Rose-Allamanda. The show is worth some fuss.