Caring for Vinca
The names vinca and
periwinkle apply both to an evergreen ground cover and to an annual flower, so
it's important to know the differences between the two plants if you want
success in your garden. Vinca minor, also known as common periwinkle or
creeping myrtle, is the ground cover plant often used where grass won't grow.
Vinca roseus, the Madagascar or Rose periwinkle, is the annual plant used in
sunny flower beds and containers. Both plants are commonly found in garden
centers in the spring and summer, but they are used in the garden completely
differently.
Vinca roseus (also known botanically as Catharanthus roseus) is an African native commonly referred to in the U.S. as Madagascar periwinkle, Rose periwinkle, or just Vinca. While technically a tender perennial in USDA Zones 9 and 10, it is almost always used as an annual and replaced every year, even in those zones. It is deer-resistant and easy to grow in almost any sunny spot. It sports attractive shiny green leaves with a white rib down the middle, and large white, pink or violet flowers, often with a pink center. They make mounded plants 1 to 2 feet high and wide, and bloom reliably all summer.
Growing Annual Vinca
Annual periwinkles love the sun and tolerate
only very light shade before flowering is affected. Use them for bedding in
flower beds, in outdoor containers, or as houseplants for sunny windows. When
bedding out, space them 8 to 10 inches apart. They are not particular about
soil, and in fact do well in poor soil with low fertilization. Watering is
necessary only if plants start to droop. When used in containers, they do best
in terra cotta pots which allow for good drainage and air flow; be especially
careful not to overwater if grown in plastic pots. They are pest-free if not
overwatered. The plants are self-cleaning, so you do not have to dead-head
spent flowers, but plants can be pinched back to encourage bushiness if they
get too large. They are completely intolerant of frost, so if you want to bring
them in for the winter, be sure to move the plants indoors when night
temperatures drop down to about 50 degrees. Plants can be propagated by stem
cuttings at any time, or you can start from seed three to four months before
the last frost date for your area. Periwinkles are easily found in garden
centers in late spring.
Vinca, The Shade-Loving Ground Cover
Vinca minor, the common periwinkle or creeping
myrtle, is an evergreen vine from Europe and Asia. It is a common ground cover
in the United States and lower Canada, often used in areas where lawn grass
will not thrive, such as on banks, under trees, or in beds shaded by trees and
buildings. Its trailing stems root easily, creating a dense cover that smothers
weeds while allowing larger plants like shrubs and bulbs to grow well. The
small leaves give the plant a fine texture that blends well with larger-leaved
ground covers like ivy and pachysandra. Early spring blooms are either white or
shades of blue. It is hardy in USDA Zones 4 through 10.
Growing Ground Cover Vinca
Vinca minor grows best in shady, well-drained
soil, but once established, it tolerates a wide range of sites. Do not plant in
full sun south of USDA Zone 7. You can find vinca in garden centers in spring
and fall, usually as rooted cuttings in flats. Plant 12 inches apart, feed
lightly with an all-purpose garden fertilizer, and mulch the first summer to
keep down weeds. Water to keep moist the first summer but avoid wet soil to
prevent fungal diseases and root rot. After the first season, little care is
necessary besides fertilizing lightly in spring and watering during extended
droughts, although vinca grown in sun may require occasional watering.
Propagate by stem cuttings at any time or by division in spring. No special care
is needed in winter.
Precautions
Annual periwinkles have been used for centuries
for folk medicine, especially for treating diabetes, and are the source of
several cancer drugs. Use them with caution in gardens that are accessible to
small children.
Ground cover vincas can be exuberant growers, so
give them plenty of room to spread, and trim back if necessary to contain them.