Flowering Dogwood (Cornus florida)

Flowering Dogwood

Flowering dogwood (Cornus florida) is a small North American tree renowned for its wide canopy and plentiful spring blooms. Individual white or pink “flower” is actually a flower head that contains four oval bracts and a cluster of tiny yellow true flowers. Because of its decorative canopy, prolific spring blooming, and attractive red autumn leaves and berries, it is the most popular native tree in US gardens.

I. Appearance and Characteristics 

The flowering dogwood is usually included in the dogwood genus Cornus as Cornus florida L., although it is sometimes treated in a separate genus as Benthamidia florida (L.) Spach. Less common names for C. florida include American dogwood, Florida dogwood, Indian arrowwood, Cornelian tree, white cornel, white dogwood, false box, and false boxwood.

Cornus florida is a species of flowering tree in the family Cornaceae native to eastern North America and northern Mexico. An endemic population once spanned from southernmost coastal Maine south to northern Florida and west to the Mississippi River. The tree is commonly planted as an ornamental in residential and public areas because of its showy branches and interesting bark structure.

Flowering dogwood is a small deciduous tree 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. The leaves 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 of C. florida is about 80 years.

The flowers are individually small, inconspicuous, and a hermaphrodite, with four, greenish-yellow petals (not bracts) 4 mm (0.16 in) long. Around 20 flowers are produced in a dense, rounded, umbel-shaped inflorescence, or flower-head, 1–2 cm (0.39–0.79 in) in diameter. The flower-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 selected cultivars 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 similar Kousa dogwood (Cornus kousa), native to Asia, flowers about a month later.

The fruit is a cluster of two to ten separate drupes, (fused in Cornus 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 of birds, which then distribute the seeds. They are also a larval host plant for several moth varieties, including Eudeilinia herminiata, the dogwood thyatirid moth, Antispila cornifoliella, the stinging rose moth, the grand arches moth, the pecan bark borer, the dogwood borer, the rosaceous leaf roller, the diamondback epinotia moth, spring azures, cecropia moths, and the Io moth. While not poisonous to humans, the fruit is extremely sour and unpleasant-tasting. Flowering dogwood is monoecious, meaning the tree has both male and female flowers, and all trees will produce fruit.

II. How to Grow and Care

Sunlight and Temperature

Flowering dogwood prefers full sun and can grow in a slightly shaded environment. It needs 4-6 hours of sunlight per day; if it does not get enough sun, the plant will grow poorly, the branches will become lighter in color, and the number of flowers and fruit will be fewer.

Flowering dogwood is widely distributed in temperate and subtropical regions and prefers cool, moist environments. It is cold hardy, tolerating temperatures as low as -20 ℃, but fears heat. Flowering dogwood is drought-tolerant and requires little water. However, it is necessary to ensure a basic water supply in hot summers.

Watering

Water flowering dogwood 1-2 times a week. In hot summer or sunny conditions, appropriately increase the watering frequency. When the plant is dormant in winter, it absorbs water at a reduced rate, so you will need to reduce the amount of watering. When watering, be careful not to spray water on the leaves, as too much water on the leaves can cause pests and diseases.

Soil

Flowering dogwood is very adaptable, but prefers nutrient-rich, well-drained soil. If the soil is poorly drained, improve it by mixing in some sand. It grows best in neutral or slightly acidic soil with a suitable pH of 5.5-6.6.

Fertilizing

Flowering dogwood does not require much fertilizer. Too much fertilization can lead to excessive growth and weaker resistance. If the soil is poor, add a decomposing organic fertilizer in spring. If you want the tree to bloom and flourish, add some potassium fertilizer. Do not apply fertilizer in the first year of planting, because it may damage the newly grown root system. You can apply fertilizer after one year of growth.

Planting Instructions

You can transplant flowering dogwood from a pot into a garden anytime throughout the year. If you plan to transplant a seedling with bare roots, do it at the end of fall or early spring to avoid the frost. When transplanting, the planting hole should be wide enough to allow room for the roots to grow. plant at a depth of two-thirds of the soil ball, so the covered soil is slightly above the ground, which helps drainage. Water the soil well to keep it moist after planting. You can also cover the soil surface with mulch to reduce water evaporation and keep the soil cool.

Pruning

Flowering dogwood does not require much pruning. You need only to cut off dead, injured branches and any parts infected with pests and disease. Prune flowering dogwood in late fall and winter. If you prune it in spring or summer, the plant is in its growing season and the wounds will shed a lot of sap; in late fall and winter, flowering dogwood enters dormancy and will not do that.

Propagation

Cornus florida is easily propagated by seeds, which are sown in the fall into prepared rows of sawdust or sand, and emerge in the spring. Germination rates for good clean seed should be near 100% if seed dormancy is first overcome by cold stratification treatments for 90 to 120 days at 4 °C (39 °F). Flowering dogwood demonstrates gametophytic self-incompatibility, meaning that the plants can’t self-fertilize. This is important for breeding programs as it means that it is not necessary to emasculate (remove the anthers from) C. florida flowers before making controlled cross-pollinations. These pollinations should be repeated every other day, as the flowers must be cross-pollinated within one or two days of opening for pollinations to be effective.

Softwood cuttings taken in late spring or early summer from new growth can be rooted under mist if treated with 8,000 to 10,000 ppm indole-3-butyric acid (IBA). In cold climates, potted cuttings must be kept in heated cold frames or polyhouses 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 by T-budding in late summer or by whip grafting in the greenhouse in winter onto seedling rootstock.

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. 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.

III. Uses and Benefits 

  • Ornamental uses

Flowering dogwood is considered one of the, if not the, most popular flowering trees in North America. The lovely spring flowers, summer fruit, fall foliage, and elegant winter branches give it year-long beauty. Many gardeners plant flowering dogwood in groups, along borders, or as a specimen piece in cottage or prairie/meadow gardens, as its size and beauty make it very versatile. Potential companion plants are numerous and include hostas, astilbes, and azaleas.

  • Medicinal uses

Native Americans used the bark and roots in a remedy for malaria; a red dye was also extracted from the roots. The species has been used in the production of inks, scarlet dyes, and as a quinine substitute. The hard, dense wood has been used for products such as golf club heads, mallets, wooden rake teeth, tool handles, jeweler’s boxes and butcher’s blocks. Cornus florida is the state tree and flower of Virginia, the state tree of Missouri, and state flower of North Carolina. It was used to treat dogs with mange, which may be how it got its name. The red berries are not edible, despite some rumors otherwise.

In 1915, 40 dogwood saplings were donated by the U.S. to Japan in the 1912-15 exchange of flowers between Tokyo and Washington, D.C. While the cherry blossom trees survived the ensuing sour relations of these two countries and are the main feature of the National Cherry Blossom Festival, all dogwood trees in Tokyo died except the one that had been planted in an agriculture high school. In 2012, the United States sent 3,000 dogwood saplings to Japan to commemorate the 100th anniversary of the Washington, D.C., cherry trees given as a gift to the U.S. by Japan in 1912.

Flowering Dogwood (Cornus florida) Details

Common name Flowering Dogwood
Botanical name Cornus florida
Plant type Native Plant
Hardiness zone 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Growth rate Medium
Harvest time Fall
Height 15 ft. 0 in. - 25 ft. 0 in.
Width 15 ft. 0 in. - 25 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Clay
Flower color Gold/Yellow
Leaf color Green