The case could be made for saying Clematis 'Purpurea Plena Elegans' is an acquired taste. Not everyone loves double clematis, and this cultivar - in what has been known traditionally as the Viticella Group - bears the additional burden of being perceived as less than true to name. It is not purple, as the epithet so clearly implies. Those familiar with clematis nomenclature and botanical Latin will know the descriptor "purpurea" is a relative term, often used to suggest "more purple than" or "closest to purple" from amongst flowers or foliage usually of some other shade of deep pink or dusty red or even green.
For instance, we have Clematis recta var. purpurea, with indisputably deep purple new foliage (but most truly a lively reddish-brown or puce), or in the foxglove world Digitalis purpurea, which is purple by no one's definition (pink to rosy pink), but its color is a vast deal closer to purple than the unabashed golden perennial foxglove, Digitalis grandiflora. However, it is not my place to debate color, other than to say those selling this plant must spend a great amount of time explaining it. Color terms vary by country and language. In America, one must charitably call it deep dusty rose, or plum, or old rose violet, to have the hue understood.
The remainder of the name is easy enough. Plena is the commonly used Latin term for double, and elegans means elegant, fine, or handsome. Hmm... perhaps this last, elegans, might also be open for debate, too. The flowers of C. 'Purpurea Plena Elegans' are small compared to double large-flowered hybrids (5 cm / 2 inches or a bit more in diameter), and can appear shaggy if the outer sepals are much longer than the inner petaloid stamens, or if they twist, which the outer sepals often do. Describe all this to someone and they may wrinkle their nose. Show them a mature plant (3 to 4 meters / 9 to 12 feet tall or broad) decked in hundreds of blooms, and they'll ask where they can buy it. In this case, seeing is wanting.
C. 'Purpurea Plena Elegans', known by the affectionate shorthand "PPE", is attributed to the stable of wonderful Clematis viticella influenced cultivars of Francisque Morel. Its background is not entirely known, but it was introduced around 1900 by Morel before he retired and sent his remaining unintroduced crosses to William Robinson at Gravetye Manor in 1915 or shortly thereafter. PPE may have Clematis viticella 'Flore Pleno' (syn. 'Mary Rose') in its lineage, a reasonable assumption given their similarity in flower form, growth habit, and vigor. Although, it must be said there is some blue shading in C. viticella 'Flore Pleno', making it the more purple of the two. What parent gives PPE its rosier tint is anyone's guess.
In the garden, one may follow the dictates of traditional pruning advice and prune PPE to 10-20 cm (4 to 8 inches) in the winter, once it is fully dormant. Such treatment will produce a plethora of new shoots from the crown every year, making a bushy broad plant of good vigor, flowering in June and continuing a month at least. The flowers are always double and take some time to open. After 14 days more or less (less in hot weather), the outer sepals fall away, and the inner pompon lasts another week at least, usually more.
At the Rogerson Clematis Garden we have two specimens of PPE. One adorns a 1.4-meter (4 to 5 feet) tall wire fence and is treated as mentioned above. It flowers in late June throughout July. In early August it is again cut back to 10 cm (4 inches) tall, fertilized with an organic rose and flower food, and it reblooms on shorter stems in late September and throughout October until the first frost. In climates with a shorter growing season, this is not possible.
The second specimen was planted in the autumn of 2006, leaning into a mature Cornus florida, or pink dogwood. C. 'Purpurea Plena Elegans' now flowers madly in mid-May well into June (after the dogwood), at the very crown of the 8-meter (26 feet) tall tree. If we pruned this PPE hard every year, it would rarely make it to the top of the tree; on the contrary, we have never pruned this particular specimen. Without human interference, this PPE has assorted itself throughout the furthest reaches of the tree. It is followed into bloom by Clematis viticella, planted on the opposite side in 2006 and likewise never pruned.
PPE is also useful for flowing over and adding interest to those boring green garden lumps known as Rhododendrons. Planted at the drip line of the shrub, the clematis is pruned as soon as possible in late autumn, allowing the "rhody" ample winter light to form its flower buds. As the rhododendron comes into flower in April or May, the first telltale shoots of PPE can be seen rising hand-over-hand up the shrub's branches. Once the rhody is finished flowering and deadheaded, PPE forms a blanket of blossoms, enlivening an area otherwise blank of summer color. It could as easily do the same for mature lilacs.
C. 'Purpurea Plena Elegans' is such a paragon of virtue you will find it on the I.Cl.S. Recommended Clematis list, it has been necessary to lobby heavily for its continuance there (it does come down to personal taste and majority rule). No one denies its vigor and general durability, but the unwieldy and somewhat inaccurate name does the plant no favors, and there are always those who find the small but abundant flowers unkempt. That said, you will forever find me an undaunted defender of the definition-defying color and supreme utility of C. 'Purpurea Plena Elegans'.