| Cornus florida | |
|---|---|
 | |
| Flowering dogwood in Spring | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Cornales |
| Family: | Cornaceae |
| Genus: | Cornus |
| Subgenus: | Cornussubg. Cynoxylon |
| Species: | C. florida |
| Binomial name | |
| Cornus florida | |
 | |
| Natural range ofCornus florida | |
| Synonyms[3] | |
| |
Cornus florida, theflowering dogwood, is aspecies offlowering tree in the familyCornaceae native to easternNorth America and northernMexico. An endemic population once spanned from southernmost coastalMaine south to northernFlorida and west to theMississippi River.[4] The tree is commonly planted as an ornamental in residential and public areas because of its showybracts and interesting bark structure.
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Flowering dogwood is a smalldeciduoustree growing to 10 m (33 ft) high, often wider than it is tall when mature, with a trunk diameter of up to 30 cm (1 ft). A 10-year-old tree will stand about 5 m (16 ft) tall. Theleaves are opposite, simple, ovate, 6–13 cm (2.4–5.1 in) long and 4–6 cm (1.6–2.4 in) broad, with an apparently entire margin (actually very finely toothed, under a lens); they turn a rich red-brown in fall.
Flowering dogwood attains its greatest size and growth potential in the Upper South, sometimes up to 40 feet in height. At the northern end of its range, heights of 30–33 feet are more typical. Hot, humid summer weather is necessary for new growth to harden off in the fall.
The maximum lifespan ofC. florida is about 80 years.[5]
Theflowers are individually small, inconspicuous, and hermaphroditic, with four, greenish-yellow petals (not bracts) 4 mm (0.16 in) long. Around 20 flowers are produced in a dense, rounded,umbel-shapedinflorescence, 1–2 cm (0.39–0.79 in) in diameter. This centralflower head is surrounded by four conspicuous large white, pink or red bracts (not petals), each bract 3 cm (1.2 in) long and 2.5 cm (0.98 in) broad, rounded, and often with a distinct notch at the apex.
When in the wild they can typically be found at the forest edge and frequently on dry ridges. While most of the wild trees have white bracts, some selectedcultivars of this tree also have pink bracts, some even almost a true red. They typically flower in early April in the southern part of their range, to late April or early May in northern and high altitude areas. The similarKousa dogwood (Cornus kousa), native toAsia, flowers about a month later.
Thefruit is a cluster of two to ten separatedrupes, (fused inCornus kousa), each 10–15 mm (0.39–0.59 in) long and about 8 mm (0.31 in) wide, which ripen in the late summer and the early fall to a bright red, or occasionally yellow with a rosy blush. They are an important food source for dozens of species ofbirds, which then distribute theseeds. They are also a larval host plant for several moth varieties, includingEudeilinia herminiata, thedogwood thyatirid moth,Antispila cornifoliella, thestinging rose moth, thegrand arches moth,[6] the pecan bark borer,[7] thedogwood borer,[8] therosaceous leaf roller, thediamondback epinotia moth,spring azures,[9]cecropia moths,[9] and theIo moth. While not poisonous to humans, the fruit is extremely sour and unpleasant-tasting.[citation needed] Flowering dogwood is monoecious, meaning the tree has both male and female flowers, and all trees will produce fruit.
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The flowering dogwood is usually included in the dogwood genusCornus asCornus florida L., although it is sometimes treated in a separate genus asBenthamidia florida (L.) Spach. Less common names forC. florida includeAmerican dogwood,Florida dogwood,Indian arrowwood,Cornelian tree,white cornel,white dogwood,false box, andfalse boxwood.
Twosubspecies are generally recognized:
| Image | Scientific name | Distribution |
|---|---|---|
.jpg) | Cornus florida subsp.florida | Eastern and south-centralUnited States. |
 | Cornus florida subsp.urbiniana (Rose) Rickett | NortheasternMexico (Nuevo León,Veracruz). |
Dogwood anthracnose caused by the fungiDiscula destructiva has caused severe mortality of dogwoods.[10] In regions where dogwood anthracnose is a problem, homeowners and public land managers are encouraged to know the symptoms and inspect trees frequently. The selection of healthy, disease-free planting stock is essential and transplanting trees from the forest, particularly from mountain forests, should be avoided.[11] Species ofPhytophthora causeroot rot.[12]
Flowering dogwood does besthorticulturally in moist,acidic soil in a site with some afternoon shade, but good morning sun. It does not do well when exposed to intense heat sources such as adjacent parking lots or air conditioning compressors. It also has a lowsalinity tolerance. Thehardiness zone is 5–9 and the preferred pH is between 6.0 and 7.0.[13] In urban and suburban settings, care should be taken not to inflict mower damage on the trunk or roots, as this increases the tree's susceptibility to disease and pest pressure.[13]: 98–100 The common flowering dogwood has been placed on the endangered species list in Ontario.[14][15][16] Sites should be selected for reasonably well-drained, fertile soils; full sun is recommended in high-hazard areas (such as stream or pond banks). New plantings should be mulched to a depth of 5 to 10 cm (2 to 4 in), avoiding the stem. Dead wood and leaves should be pruned and completely removed and destroyed yearly. Plants should be watered weekly during droughts, with watering done in the morning, avoiding wetting the foliage. Registeredfungicides can be applied when necessary, according to manufacturers instructions and advice of localExtension Service.[17]
Flowering dogwood is grown widely throughout thetemperate world.
Cornus florida is easily propagated by seeds, which are sown in the fall into prepared rows ofsawdust or sand, and emerge in the spring.Germination rates for good clean seed should be near 100% if seed dormancy is first overcome by coldstratification treatments for 90 to 120 days at 4 °C (39 °F).[13]: 100–102 [20] Flowering dogwood demonstratesgametophyticself-incompatibility, meaning that the plants cannot self-fertilize. This is important for breeding programs as it means that it is not necessary toemasculate (remove theanthers from)C. florida flowers before making controlledcross-pollinations. These pollinations should be repeated every other day, as the flowers must becross-pollinated within one or two days of opening forpollinations to be effective.[21]
Softwoodcuttings taken in late spring or early summer from new growth can be rooted under mist if treated with 8,000 to 10,000 ppmindole-3-butyric acid (IBA). In cold climates, potted cuttings must be kept in heated cold frames orpolyhouses the following winter to maintain temperatures between 0 and 7 °C (32 and 45 °F). Although rooting success can be as high as 50–85%, this technique is not commonly used by commercial growers. Rather, selected cultivars are generally propagated byT-budding in late summer or by whipgrafting in the greenhouse in winter onto seedling rootstock.[20][13]: 102
Micropropagation of flowering dogwood is now used in breeding programs aiming to incorporate resistance to dogwood anthracnose and powdery mildew into horticulturally and economically important cultivars.Nodal (axillary bud) sections are established in a culture of Woody Plant Medium (WPM) amended with 4.4 μmol/L 6-Benzyladenine (BA) to promote shoot growth.[22] Rooting of up to 83% can be obtained when 5–7 week-old microshoots are then transferred to WPM amended with 4.9 μmol/L IBA.[23]
Native Americans used the bark and roots in a remedy formalaria; a red dye was also extracted from the roots.[24] The species has been used in the production of inks,scarlet dyes, and as aquinine substitute. The hard, dense wood has been used for products such asgolf club heads,mallets, wooden rake teeth, tool handles, jeweler's boxes and butcher's blocks.[25][13]: 100 It was used to treat dogs withmange, which may be how it got its name.[26] The red berries are not edible, despite some rumors otherwise.[27]
In 1915, 40 dogwood saplings were donated by the U.S. toJapan in the 1912–1915 exchange of flowers betweenTokyo andWashington, D.C. While thecherry blossom trees survived the ensuing sour relations of these two countries and are the main feature of theNational Cherry Blossom Festival, all dogwood trees in Tokyo died except the one that had been planted in an agriculture high school. In 2012, the U.S. sent 3,000 dogwood saplings toJapan to commemorate the 100th anniversary of the Washington, D.C., cherry trees given as a gift to the U.S. by Japan in 1912.[28][29]
Cornus florida is thestate tree and flower ofVirginia,[30] the state tree ofMissouri, andstate flower ofNorth Carolina.[31][26]
