Two plants Americans call vinca
Two different plants are sold in America as vinca, and they sit in separate genera of the same family. Annual vinca is Catharanthus roseus, an evergreen, tender, erect-to-spreading perennial in the dogbane family, Apocynaceae. It was formerly classified as Vinca rosea, which is exactly where the shared name comes from. Its native range is published two ways, Madagascar and the semi-arid regions of Africa, and both versions describe the same conditions: heat, strong light, and soil that dries. The mix-up is old and official. Catharanthus roseus was once commonly called vinca even though Vinca is a separate genus, and the perennial groundcover periwinkle is still routinely confused with the bedding plant Madagascar periwinkle.
The genus Vinca is a separate group of about 12 species, and two of them became the groundcovers Americans actually plant. Vinca minor, lesser periwinkle, is native to Europe and the Caucasus and creeps flat across the soil. Vinca major, greater periwinkle, ranges from southern France to Asia Minor and forms a dense mat. Both answer to periwinkle, to vinca, and across much of the country to myrtle, so the word on the tag settles nothing at a rack of garden flowers. Where the plant is stocked settles it instead. The perennial Vinca species are also called vinca or periwinkle, and they perform best in shady areas, so they sell as groundcover in flats of rooted, trailing pieces, while the annual arrives in summer six-packs for full sun.
Which vinca is in the pot
The flower and the leaf edge settle the identification faster than the label does. Three plants come home under the word vinca, and each carries one detail the other two do not.
Does vinca come back every year
Annual vinca is a perennial that almost nobody gets to keep. It is winter hardy in zone 10 and higher and treated as an annual in colder regions, with its range listed as 10a through 11b and as 10 to 11, where it grows as a woody based perennial. In the continental United States that means south Florida, the southern tip of Texas, the low desert, and a strip of coastal California. Even inside that range the plant often lasts a single season: in Florida periwinkles are treated as annuals because they rarely thrive beyond one summer, lost to frost or to fungal disease. Everywhere colder, the first hard freeze ends it and nothing resprouts from the crown. What does return is seed. The plant may self-seed in optimum growing conditions, and the seed often self-sows around the garden the next year, which is what most gardeners are looking at when they report that their vinca came back. Potted plants can be overwintered indoors, and cuttings taken in late summer hold stock for the following spring.
The groundcover periwinkles are hardy perennials and behave like it. Vinca minor carries two published hardiness ratings, 4a through 9b and 4 to 8, so zone 4 is the agreed cold limit and only the warm end is in question; once a planting takes, the same plants thicken season after season with no replanting. Vinca major is hardy only from zone 7, listed as 7a through 9b and as 7 to 9. North of that it can still be grown in containers.
Telling vinca and impatiens apart
Light separates them before any leaf is examined. In the South, annual vinca is as important for planting in hot, full sun locations as impatiens is for shady ones, and swapping the two is the most common way both end up looking bad by July. The leaves confirm the call. Annual vinca leaves are opposite, simple, and smooth-margined, oblong to elliptic-oblong, hairless, glossy, with a pale midrib running down the center. Flower size helps too, since annual vinca flowers run 1 to 3 inches across and sit flat and open on the plant. Impatiens is not the only look-alike either: annual vinca is also confused with phlox, star jasmine, and both periwinkle species. Water is the second difference and the one that actually kills plants. Annual vinca wants soil that dries between waterings and carries moderate to high drought tolerance, which is what lets it hold a full-sun bed through a dry August.
Why vinca turns yellow and collapses
Yellow leaves that turn into wilting and collapse trace back to water more often than to anything else. Annual vinca is one of the most trouble-free bedding plants, and the diseases that do reach it are root rots, stem rots, and foliar diebacks that follow poor drainage. Frequent watering makes conditions favorable for branch blight and root rot even on moderate to dry sites, and light, frequent waterings encourage the stem rot pathogens by raising humidity right at the base of the stem. The progression is consistent: leaves yellow and scorch, growth turns poor, plants stunt, and then they wilt and die, with reduced root systems underneath and individual roots sloughing off their outer tissue to leave the inner core behind. Planting into cold ground starts the same sequence early, since vinca set out before the soil warms often develops fungus problems or root rot.
Several organisms produce that same picture, and they are hard to separate in a bed. Aerial stem blight and root rot come from Phytophthora, which puts dark brown to black lesions on stems and branches so that everything above them wilts and dies back, frequently with no root rot involved at all. Earlier on, the same disease shows as water-soaked, greasy lesions on the foliage and at the base of affected shoots, with individual shoots wilting and weakening before reddish, dark brown cankers appear on the stems. The organism goes by two names, Phytophthora nicotianae and Phytophthora parasitica, for one soil-borne problem already present in southern soils. Rhizoctonia causes a stem rot that turns plants yellow, wilts them, and collapses them, with a slower and more subtle root rot behind it. Pythium, a close relative of Phytophthora, gives similar root rot and damping off of seedlings but no branch blight.
Two further causes look like the same yellowing. Black root rot, caused by the fungus Thielaviopsis basicola, is uncommon on vinca in home plantings but arrives on infected material or in beds where more susceptible hosts such as pansies have already died, and it leaves small root systems with a salt-and-pepper appearance. High pH soils increase its severity, which is why lime goes down only if a soil test calls for it. In the desert Southwest the yellowing usually has a chemical cause. Most desert soils sit at a pH of 8.0 to 8.5, and in that range iron solubility is so reduced that plants cannot take iron up even where the soil holds plenty of it. Chelated iron in the Fe-EDDHA form stays effective in high pH soil where Fe-DTPA and Fe-EDTA do not.
Yellow leaves when the watering is already right
Once the soil moisture has been corrected and the bed still turns yellow, the cause is narrowed by looking at the pattern on the plant.
Planting annual vinca
Wait for warm soil before anything goes in the ground. Annual vinca can be planted outdoors once soil temperatures are above 60 degrees Fahrenheit, and spring soil lags weeks behind spring air, so a warm stretch of April afternoons is not the signal. It goes in later than the petunias and pansies that handle cool ground, and the delay costs nothing, because the plant does its real growing in heat. Space transplants about 12 inches apart, and no closer than 10 to 12 inches, since crowding limits air circulation between plants and favors disease. Pick the bed for drainage first. Water standing after a storm, the run-out from a downspout, or an edged bed that traps runoff will cost the planting no matter what else is done right. Do not plant vincas in the same bed year after year, because the organisms that rot them stay in the soil once a planting has failed there.
Vinca wants acid soil. The preferred range is a pH of 5.5 to 6.0, with higher pH tolerated in practice, and 5.5 is the recommended planting pH in Louisiana beds; the listed soil preference for the plant is simply acid, below 6.0. Improper pH increases disease problems with vinca, which is the reason to test a bed before liming it. Containers follow the same logic with less margin for error. Use a mix that dries between waterings and a pot with open drainage, never leave a saucer standing full underneath, and set trailing types where they can spill over an edge, clear of wet potting mix. Then mulch with pine straw, which decreases splashing of rainfall and irrigation water from the soil onto the lower stems and foliage.
When the ground is warm enough, by region
Soil temperature sets the planting day and the calendar only approximates it, so the states that grow the most vinca name the month that usually meets the threshold.
Keeping annual vinca in flower
Annual vinca keeps flowering on its own, and most of what gardeners do to help reduces the display. Spent flowers do not require deadheading to encourage more blooms, and the plant does not need pinching to maintain a tidy growth habit; removing old flowers is not necessary and will not promote new growth. Feeding is the more expensive mistake. Vincas are very light feeders that do not require fertilizing through the season, and fertilizing can reduce the number of flowers produced, so where a feed is used at all it goes on at half the recommended rate. Heat is not the enemy people expect it to be: the plant blooms even during heat stress, which is why it holds a bed through a southern August alongside geraniums and the other summer standards. A slow start is normal. In New England, annual vinca often starts slow and reaches peak flowering in July and August, so a flat that looks unimpressive in June is usually on schedule. When bloom does fall off, look at light first: leggy growth is usually a sign the plants are not getting enough sunlight.
Vinca series worth knowing apart
Series names on the tag carry real differences in height, habit, and disease resistance. The palette used to run to three colors, white, white with a red eye, and a rosy purple, and the breeding that widened it also produced the disease-resistant groups.
Periwinkle as groundcover, and where it takes over
Periwinkle is planted to cover ground that will not hold anything else, and it does that faster than most gardeners plan for. Vinca minor spreads by sending out long, trailing, rooting shoots that make new plants wherever they touch soil. Its rapid growth rate and its ability to root at the nodes let it form a dense mat over a wide area and become weedy and high maintenance in short order. Spacing sets the pace. Rooted cuttings and established plants are normally spaced 12 to 18 inches apart, with 8 inches used for quick cover of a small area and 12 to 18 inches for large ones. At a 6-inch spacing, periwinkle will completely cover an area in one year. Disease is the one thing that reliably stops a mat: a patch that browns out in sections while the rest stays green is failing, and the dead growth comes out before new runners cross it. Periwinkle is susceptible to dieback, in which plants wilt and die back to the ground from fungal disease, and vine stem canker, also called blight, can damage or kill large patches.
That vigor is why both species appear on invasive lists. Vinca minor's aggressive nature has won it a spot on many states' most unwanted lists, and both species are classified as invasive in North Carolina. Vinca major is considered invasive in Virginia, South Carolina, Georgia, Alabama, and California, and in Florida both species are rated invasion risks and are not recommended. In California it is rapidly spreading through most coastal counties, foothill woodlands, the Central Valley, and even desert areas, having escaped garden plantings and lowered species diversity in native plant communities, where it carries a Moderate invasiveness rating. Riparian zones are particularly sensitive, because fragments of the vine break off, wash downstream, and start new colonies wherever they land. The plant can escape cultivation and is considered invasive in certain areas, so local laws and recommendations are worth checking before it goes in. Containment is part of the plan wherever it goes in on purpose, and Vinca major is best used as an annual for pots, baskets, and containers, where its spread can be monitored and controlled.
Sun or shade for vinca
The two vincas want opposite light. Annual vinca needs a location with full sun for 8 or more hours a day, and eight hours of direct sun daily is the same standard applied to it in Louisiana. In New England it must be grown in full sun and well-drained soil to perform at all, and hot summer weather helps it to the best growth and flowering. A bed under a tree canopy, on the north side of a house, or in the shadow of a fence for half the afternoon will give leaves and few flowers. The groundcover is rated two ways: Vinca minor tolerates high heat and nearly full shade while preferring full sun, partial shade, or dappled sunlight with moist, well-drained soil, and it is also rated as preferring shade while still growing well in full sun, with foliage color richer green in partial shade and more flowers produced in the sun.
How much water vinca wants
Vinca wants less water than almost anything else in a summer bed. Water only when the top 1 to 2 inches of soil are dry, which in a bed with real drainage can mean skipping several days in a row of hot weather. Timing and aim matter as much as volume: keep the watering out of the late afternoon so the soil has a chance to dry before night, and put it on the soil while the foliage stays dry, which is what holds mildew off. The same restraint applies to the groundcover, which likes to be kept on the dry side and will rot at the roots if it is irrigated too frequently. A finger pushed into the soil beside the plant settles the question faster than any schedule, because a container in afternoon shade and a container in full sun dry at completely different rates.
How big vinca gets
Annual vinca is a knee-high mound at most, and the published sizes differ because the series differ. Figures for the species run 7 to 24 inches high and wide, with either a carpet-like or an upright habit, while the usual garden size is 10 to 18 inches tall with a spread of about a foot, and about 2 feet for the trailing types. Plants of 1 or 2 feet high and about the same across are standard too, with the newer spreading types wider and lower and most of them forming a dense, rounded shape, and the habit runs erect to low spreading, to 18 inches. An upright series fills a bed at knee height, a spreading series stays low and runs wide, and the series name on the tag predicts the size better than the word vinca does. The groundcovers are ankle height and are measured instead by how far they run. Vinca minor grows 3 to 6 inches high and 3 to 18 inches wide, or about 6 inches tall as a rounded figure. Vinca major grows 3 to 8 inches high and 1 to 2 feet wide, and where it is happy it mounds up to 2 feet, which is the difference a gardener feels when a mat that was supposed to stay flat starts swallowing the front of a border.
Toxicity and pet safety
Vinca is poisonous, and the listings cover cats, dogs, horses, and people. Annual vinca is rated a low-severity poison, and it appears as a problem for cats, dogs, and horses and as poisonous to humans. Consuming large quantities of the plant leads to vomiting, diarrhea, low blood pressure, hallucinations, depression, tremors, seizures, coma, and death, with vinca alkaloids as the toxic principle. The ASPCA rates it toxic to dogs, cats, and horses and gives the same clinical signs under both of the names it files the plant under. How much was eaten decides how serious it is, so a chewed leaf is a call to a veterinarian or a poison-control line, with vomiting and low blood pressure the first signs to watch for. The same chemistry made the plant famous in medicine. Compounds in Catharanthus roseus led to a breakthrough in the treatment of certain kinds of leukemia, and its extracts are used in modern medicine to treat some cancers, which is why it turns up in herb garden plantings. Those are purified pharmaceutical products dosed under supervision, and no part of the garden plant is safe to eat, to brew, or to give to an animal.
Growing more vinca
Seed is the standard route for the annual and cuttings for the groundcover. Seed is the recommended propagation strategy for annual vinca, and it germinates in 7 to 21 days at 70 to 75 degrees Fahrenheit, steady warmth that a cool spring windowsill rarely supplies without a heat mat. Cuttings work as well and root in about 3 to 4 weeks: take 4 to 6 inches off the top of a stem that carries no flowers, strip the lower leaves, and set it to root. For the groundcover, division and stem cuttings are the recommended methods, done as tip cuttings of non-flowering stems in late spring or by dividing plants at any point in the season. An established periwinkle patch supplies its own material, since every node that has rooted into the soil is already a plant.
Pests and diseases
Insects are the smallest part of vinca's trouble. The annual is reported to have no serious insect or disease problems, with stem rot, leaf spot, and aster yellows the exceptions, and slugs and snails the animals worth watching in damp weather. Browsing mammals mostly pass it by: annual vinca is resistant to deer and rabbits, and Vinca major is listed as deer resistant as well. One disease on the groundcover reaches past the garden bed. Vinca major is a known host of a bacterium that causes Pierce's disease, which is deadly to grapevines, so a mat of greater periwinkle under a backyard grape or along a vineyard edge is a genuine liability.
What goes wrong most often
Ordered by how often each complaint appears in a sample of forty-one homeowner threads on Houzz, Garden.org, Dave's Garden, GardenWeb, extension question desks, and smaller boards.
Twenty-five of the forty-one threads, far ahead of everything else. Owners describe a bed that looked healthy on Monday and flat by the weekend, and most mention watering daily through a hot spell beforehand.
Four threads, all asking how to remove an established patch. Owners report repeated smothering, solarizing, and herbicide, because roots and stem fragments keep resprouting.
Three threads, posted in a hurry after a dog or cat chewed a leaf or a flower, with the owner trying to work out how serious it is before calling anyone.
Two threads asking whether to cut a stretched plant back, both from gardeners who had placed the plants where a wall or a canopy takes part of the day.
Two threads from buyers holding a flat and asking whether it will cope with part shade, which is the question the shared name creates at the register.
One thread from an owner who treated the annual as a returning perennial and found bare soil in spring.
One thread from a shopper who swapped one for the other and wanted to know what changes about the care.
When vinca blooms
Annual vinca flowers from the arrival of real heat until frost, and the published start dates spread across two months. The published windows are May to frost and June to frost, with the peak display given as July through September, stopping only at frost. The spread is geography more than disagreement, since the plant does nothing until soil and nights have warmed, which happens weeks apart between the Gulf and the upper Midwest. Periwinkle runs on the opposite calendar. Its bloom is given as mostly March to April with a sometimes-repeat in fall, and as May to June, and the small, blue-lavender flowers show against dark green leathery foliage in spring and early summer, then intermittently through the rest of the year, with bumblebees working them. That is the shade that puts periwinkle on most lists of purple garden flowers. Vinca major flowers April to May, its blue, funnel-shaped flowers borne in abundance in early spring and sporadically through the summer.
Where the names come from
The name Vinca is older than any of the American nicknames stacked on top of it. The genus name comes from Latin meaning to bind or wind around, a reference to the long, flexible stems that were used in wreath making. The species names describe size: minor means smaller, and Vinca minor does carry the smaller leaves of the two, while major means bigger or larger. The annual's epithet points at color instead. Roseus is read as pink and as rose colored.
Four things gardeners get told about vinca
Each of these comes up in garden centers and forum threads often enough to cost people plants.
The myth: A tag that says periwinkle means the shade groundcover.
The reality: The poison-control listing for Vinca and the separate listing for Periwinkle both give the scientific name Vinca rosea, the annual's old name, so even reference material carries the confusion the shelf label creates.
The myth: Vinca loves heat, so it needs water every day in July.
The reality: Deep supplemental irrigation once, or possibly twice, a week covers it, and only when rainfall has not supplied an inch of water in the week.
The myth: A vinca planting that starts yellowing needs an insecticide.
The reality: Neither the annual nor the perennial groundcover has any significant insect pests, so a spray aimed at insects treats a problem the plant almost never has.
The myth: Modern vinca has been bred past the disease that used to kill it.
The reality: Resistance belongs to particular series. Cora and Nirvana offer increased disease resistance over the older varieties, a degree of protection that travels with those plants and not with the species, so an unlabelled flat gets none of it.
Flower photos
FAQ
Does vinca need full sun, or will it grow in shade?
It depends which vinca. Annual vinca needs full sun for 8 or more hours a day and gives foliage and few flowers anywhere darker. The groundcover periwinkles take shade, though the ratings disagree over whether they prefer it, and they carry more flowers in sun.
Is vinca an annual or a perennial?
Botanically the bedding plant is a tender perennial, and it lives as one only in zone 10 and higher; in colder regions it is treated as an annual. The periwinkle groundcovers are hardy perennials.
Will my vinca come back next year?
The annual does not resprout from its roots outside its hardy range, though its seed often self-sows around the garden the next year and looks like a return. Periwinkle genuinely comes back, hardy from zone 4a through 9b.
How do you tell vinca from impatiens?
Start with the light the spot gets. Annual vinca fills hot, full sun beds the way impatiens fills shady ones. Then check the leaf: vinca's is hairless and glossy with a pale midrib.
What does an overwatered vinca look like?
Scorched yellow leaves and stalled, stunted growth come first, then wilting and death. Lift one plant to confirm it: the root system will be reduced, and the individual roots slough their outer tissue off the inner core.
How do you save a dying vinca bed?
Cut the watering back first, because frequent watering favors branch blight and root rot even on moderate to dry sites. Pull the collapsed plants, and do not plant vinca in that bed again the following year.
Does Cora vinca come back every year?
No. Cora is the same tender species, hardy only in zone 10 and higher. What the group adds is disease resistance, rated good against phytophthora root rot, stem rot, or aerial blight, which buys a longer summer and nothing at all in winter.
Do trailing vincas bloom all summer?
Yes, on the same schedule as the upright types, with published bloom running May to frost or June to frost and the display strongest once heat sets in.
What is the best fertilizer for vinca?
Little or none. Vinca is a very light feeder, no feeding is required across the season, and a fed plant can carry fewer flowers, so anything applied goes on at half the recommended rate.
Is vinca poisonous to dogs and cats?
Yes. It is rated toxic to dogs, cats, and horses, and it is listed as poisonous to humans as well. Call a veterinarian or a poison-control line if a pet has eaten any of it.
Is periwinkle groundcover the same plant as annual vinca?
No. Annual vinca is Catharanthus roseus; the groundcovers are Vinca minor and Vinca major, two of about 12 species in a different genus. On the ground the split is light and lifespan, since the perennial Vinca species perform best in shady areas and hold the same planting for years.
Interesting tips
- The largest-flowered vinca a home gardener can raise from a seed packet is the Mega Bloom series, 8 to 10 inches high and 10 to 12 inches wide, bred to take heat and humidity and rated highly disease resistant.
- Two periwinkle cultivars are worth hunting down for color other than blue: Vinca minor '24 Carat' for the gold of its young leaves, and Vinca major 'Variegata' for violet blue flowers over its marked foliage.
- The Cora series was the first vinca bred to resist the aerial Phytophthora fungus, a disease that until then limited how much the plant could be used in Texas gardens.
Related Guides & Flowers
Pink flowers
Pink is the color vinca was named for, and this page collects the other pink garden flowers that hold a summer bed.
Bougainvillea
The other heat and drought plant for the hottest, driest corner of an American yard.
Honeysuckle
Another garden favorite with an escape problem, and the same question about where it is safe to plant.
Foxglove
A second common ornamental whose whole plant is poisonous, worth reading before a bed goes in near children or pets.