petiole 5-20 mm long20mm is over 3/4 of an inch.
Periwinkles are popular ornamental groundcovers [10,37,68]. Their establishment in North America is largely due to their escape from cultivation [29,42,50,51,55,92,97,100,103,107]. Common periwinkle is easily propagated by cuttings [66]. Common periwinkle was planted for erosion control near Washington, DC [37]. Periwinkles are valued medicinal herbs (reviews by [7,81]), and common periwinkle is considered an aphrodisiac (review by [81]).
Swayback said:
I'm just unsure how insidious vinca can be, hopefully it's nothing like wintercreeper!
Damn that stuff! And the lazy know nothing landscapers that have riddled the countryside with it...
Periwinkles are "fairly deep-rooted" (review by [79]). Common periwinkle plants in western Montana exhibited fibrous roots ranging from 1 to 3 inches (3-8 cm) long [96]. Further descriptions of roots were unavailable as of 2009.