Ivy classification - the Pierot system
Numerous ivy cultivars
Une classification des lierres s’avère nécessaire car le lierre a cette capacité merveilleuse de faire ce que l’on appelle des “mutations”. C’est-à-dire de faire apparaître des formes ou des couleurs nouvelles. Souvent il s’agit d’une simple tige qui n’est pas comme les autres. Il suffit alors de la bouturer et de la multiplier. Parfois, il s’agit d’une forme nouvelle découverte dans la nature. Ainsi naissent spontanément de nouvelles variétés de lierre que nous pouvons sélectionner et multiplier.
Il en résulte de très nombreux cultivars. Sans doute entre 1000 et 2000. Leur nombre est difficile à établir, car tous les cultivars proposés par les pépiniéristes du monde entier ne sont pas nécessairement référencés. Par ailleurs, il existe de nombreux cultivars qui portent des noms différents, mais qui sont en réalité les mêmes. Le livre (malheureusement épuisé) publié par la Royal Horticultural Society, “Hedera The Complete Guide” de Hugh McAllister et Rosalyn Marshall, liste plus de 2000 cultivars, synonymes compris.
A classification of ivy: the Pierot system
To help you find your way among all these ivy varieties, a classification system has been created by Suzanne Warner Pierot, founder and first president of the AmericanIvy Society. This system is based mainly on leaf shape. It has the advantage of being simple and straightforward to read. However, since nature is often more complicated than our simplistic human classifications, the same cultivar may be classified in several categories.
The Pierot system consists of 9 categories:
- Adult ivies - All ivies that have progressed from their juvenile climbing stage to the ultimate shrub stage with flower and fruit production.
- Bird's foot ivies : these are ivies whose leaves are composed of very narrow, deep lobes, like bird's feet.
- Curly ivies: refers to ivies whose leaves are not flat, but wavy, curly, folded or hemmed.
- Fan ivies - Fan ivy: ivy with broad, fan-shaped leaves.
- Heart-shaped ivies - Lierres en forme de cœur: ivy with a heart-shaped leaf base.
- Ivy-ivies - Type ivy: refers to all ivies that have retained the typical shape of common ivy, flat leaves with 3 to 7 lobes.
- Miniature-ivies - Miniature ivies: ivies with small leaves, usually less than 2.5 cm long.
- Oddities - Curiosities : ivy whose leaves take on original, unusual shapes.
- Variegates ivies - variegated ivies: Ivies whose leaves are tinted with multiple colors.
As you can see, this ivy classification system is highly accessible, even to the uninitiated. That's what has made it so successful. Created in the early 1970s, it is still very much in use today.
But as you might guess, ivy can be variegated and curly, or miniature and bird's-foot. In these cases, it's best to indicate the major classification and complete with the secondary classification(s).
Pittsburgh ivy
Among all the mutations that ivy has offered us, there is one that has been particularly successful. It's a mutation selected by Paul Randolph in Pennsylvania. It is unique in that it is highly branched, generating stems emerging from each leaf axil, unlike many other ivies, which form long stems with very few branches. This particular ivy was named 'Pittsburgh'.
Ce cultivar a une autre particularité très intéressante, c’est qu’il a une forte tendance à muter, à former ce que les botanistes appellent des “sports” (c’est-à-dire des mutations). Il en est résulté quantité de nouveaux cultivars dérivant de ‘Pittsburgh’, au point que l’on peut en faire une dixième catégories de classification des lierres. Ce sont des lierres qui ont le plus souvent un port buissonnant et dense.
