The phrase “periwinkle” typically applies to Vinca major and Vinca minor. Vinca major, or big periwinkle, is winter hardy in U.S. Department of Agriculture planting zones 7 through 9. The common or lesser periwinkle, Vinca minor, might be referred to as creeping myrtle and grows in USDA zones 4 through 9. While both plants are separate species within the genus, they have a whole lot in common. Periwinkles spread quickly, providing excellent groundcover and erosion prevention. Prolific reseeding habit assures that the plant’s return in spring, even in bitter spaces which kill it back completely. You will want to prune the enthusiastic periwinkles during the growing season to keep them well in hand.
Prune periwinkles back to approximately four inches tall with clean, sharp shears in early spring to reduce the plant’s natural trend toward ranginess. Do this immediately following the final predicted frost to your area and before new growth begins. Cut back big, thick, well-established patches of Vinca with your mower set to three or four inches high.
Feed periwinkles after pruning to encourage rapid, vigorous new growth. Utilize an all-purpose balanced 10-10-10 fertilizer. Follow the packaging instructions. These plants need only one annual feeding. Do not over-fertilize them; also much plant food boosts lush foliar growth with decreased flowering in periwinkles.
Pinch or trim off flowers as they fade through summer and spring to convince the plant that it’s reproductive job is not finished. The periwinkle responds to deadheading with ongoing blooming, therefore extending the flowering season considerably and keeping the plant’s look tidy.
Trim back long or lanky stems to points of origin as they happen to keep periwinkle plants looking appealing. Cut out damaged or dead growth as needed.
Prune back runners with clean, sharp shears as they sprout wherever you want to reduce periwinkle spread throughout the growing season. These plants root easily from any stem nodes that come into touch with garden dirt. Pruning runners also promotes fullness. Pull the frozen nodes and discard or destroy them; do not toss them onto the compost heap where they are sure to take hold and prosper.
Shear periwinkles back to approximately six inches tall in late summer when the plants become overgrown or untidy. Do not prune periwinkles during the autumn or winter, as pruning produces flushes of tender new shoots that are easily damaged by cold temperatures.