May 3, 2007
Many Dogwood Types Can Thrive in Our Area
By Roberta Stewart The Planter's Palette
If you've driven south through Illinois, Indiana, or Missouri in March, the wonder of spring flowering trees surely has refreshed your winter soul. Especially resplendent is Flowering dogwood (Cornus florida), which abounds in Zone 6, one zone south. It grows here, too, but with neither the vigor nor abundance seen in a warmer climate.
Cornus florida is a "standard bearer," against which all other dogwood trees are compared. It is beloved for many reasons - bloom, fall color, fruit and bark, as well as its strong horizontal and low- branching habit.
In northern Illinois, flowering dogwood requires protection from extremes of sun, drought, and cold. Diseases such as anthracnose can be thwarted with moist, well-drained soil amended with acid. A layer of mulch keeps roots cool and evenly moist. This is good for all dogwoods, but essential for flowering dogwood.
Leaves of flowering dogwood layer upon horizontal branches, lending deep shade when sited in sunnier locations. It prefers to be planted in shade, where it will have an airier appearance.
In late April, before leaves open, it bursts into bloom. Small flower clusters cradle within four heart-shaped bracts, forming a 3- to 4-inch bloom. The creamy-white bracts are eye-catching. Fruit develops from the blossoms, ripening to a glistening red in September or October.
As fall progresses, leaves turn red-purple, then drop to expose a coarse-textured bark that hangs like nuggets on the trunk. This bark adds to the horizontal winter appeal - a mature tree spreads broadly beyond its 25-foot height. This species is worth the extra care in siting that it requires in zone 5.
Chinese or Kousa dogwood thrives better in our area. Cornus kousa has some features in common with flowering dogwood, including four showy bracts that surround the flower.
Bracts of Kousa are pointed and, unlike the C. florida, don't appear until after leaves have unfurled, usually in early June. This can be an advantage when it comes to occasional late frosts. The 2- to 4-inch blooms sit decoratively on top of the leaves, with bracts accenting the horizontal branches from base to tip-of-tree for up to six weeks.
The profuse blooms develop into 1-inch raspberry-red fruit ripening from August to October. Fruit is edible and is attractive to birds. Fall leaf color is a beautiful deep red.
Advantages of Kousa dogwood include its tolerance of more sun and its resistance to anthracnose. This allows broader siting choices, though cultural requirements mentioned for flowering dogwood must still be adhered to for it to truly thrive. Because it can tolerate full sun, it can create shade for outdoor living areas.
Kousa dogwood is more upright, stiffly when young. With age it becomes rounded and spreading. Mosaic bark on older trunks - rich brown, tan, and gray - adds character, especially when wet or in winter. Similar to flowering dogwood, it grows 20 to 30 feet tall, though usually not broader.
A weeping Kousa cultivar, C. kousa Elizabeth Lustgarten, adds interest as a specimen planting. Its beautiful flower bracts line branches that arch out and downward. Given this habit, it generally stays smaller, growing only to 15 feet.
The greatest development comes from Rutgers University, where six hybrids were developed from flowering dogwood and Kousa dogwood. They combine the best features of each - flowering dogwood's stronger horizontal branching habit and the disease resistance of Kousa dogwood. Like their parents, these hybrids will mature to 20 feet or slightly taller.
Rutger's trees bloom earlier than the Kousa, midway between the bloom times for the parents. Because of hybridization, the flower is sterile and trees will not set fruit. This can be viewed as either desirable or a drawback. If you prefer not to attract birds, then the hybrids are for you.
Each hybrid offers variations on its parents' blooms, some with pointed bracts, others with more rounded bracts. One outstanding variation comes with hybrid Stellar Pink (Cornus x Rutgan). It has Kousa's pointed bracts, but with a distinctive soft pink color. Another, Constellation (Cornus x Rutcan), has beautifully full, rounded bracts similar to the flowering dogwood, in a soft white.
The formal names of these Rutgers Hybrids are similar and can get confused in the trade-as Rutgan and Rutcan mentioned above. Shop for trees when bracts are showing, if possible, to confirm that your tree blooms pink or white, as you wish.
Last but not least
There are two more 20-foot tree forms to consider. Their blooms lack showy bracts, but these trees abound with large clusters of flowers.
One is Cornus mas, or Corneliancherry dogwood. Of all Cornus species, it is the most durable and longest-lived for Midwest use. It tolerates heavier clay soils, withstands sun or part shade, and has cold hardiness to Wisconsin's zone 4.
It is an early-spring standout. More upright in habit, its multiple trunks extend into fine stems that bear myriad yellow flower clusters in March. The fruit ripen to a bright cherry-red in July. This fruit not only provides a snack for birds, it can be made into preserves or syrup-if you get there first. The cultivar, C. mas Golden Glory, is especially suited to the Chicago area.
Would I forget the Pagoda dogwood? Not a chance! Cornus alternifolia is renowned for its strong horizontal branching with white flower clusters sitting atop glossy leaves in June.
Don't think of dogwood strictly as a shrub or a southern tree. Many types of dogwood trees will thrive in our area. Just give them some tender loving care and enjoy their beauty - without the drive south.
- Roberta Stewart is a horticulturist and woody plant specialist at The Planter's Palette, 28W571 Roosevelt Road, Winfield, IL 60190. Call (630) 293-1040.
(c) 2007 Daily Herald; Arlington Heights, Ill.. Provided by ProQuest Information and Learning. All rights Reserved.