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Gardening Answers Knowledgebase

Search Results for ' Cornus florida'

PAL Questions: 3 - Garden Tools:

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Keywords: Cornus kousa, Cornus florida, Powdery mildew diseases, Trees--Diseases and pests

PAL Question:

Where can I find information about dogwood hybrids, especially crosses between Cornus kousa and C. florida? Won't these trees be more resistant to the mildew affecting many dogwoods?

View Answer:

In addition to powdery mildew, many dogwoods can suffer with anthracnose. In his book Dirr's Hardy Trees and Shrubs (Timber Press, 1997), Michael Dirr mentions Rutgers Hybrids (which are a cross of the kousa and florida species of Cornus). These trees were developed at Rutgers University by Elwin Orton, and are resistant to dogwood anthracnose. here is an article about these cultivars, written by Orton. This article from North Carolina State University Extension discusses powdery mildew resistance. Scroll to the second table at the end which charts cultivars and their resistance or susceptibility to powdery mildew.

Oregon State University provides information about each of the six hybrids of C. florida x C. kousa. Two of the trees on this list are resistant to powdery mildew.

Clemson University Extension offers further information about the insects and diseases affecting dogwoods.

Season All Season
Date 2008-01-17
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Keywords: Cornus florida, Cornus nuttallii, Cornus

PAL Question:

I have a 22-year-old Eddie's White Wonder Dogwood. It bloomed the first three springs after planting and then stopped blooming until this spring.

It is planted at the edge of a woodland, facing south. It received summer water the first few years, but not since then, because Sunset Western Garden Book advised re: Cornus nuttallii, part of Eddie's cross: "Give infrequent summer water."

I did water it more last summer, as it was so hot and dry in our area. And it finally bloomed!

My question--Do you think that the bloom this spring was the result of more water during the summer, or did the tree have to reach a certain age to start blooming each spring?

View Answer:

There are several reasons that Dogwoods fail to flower. Flowering dogwood does need regular water, according to Sunsetís 2001 edition. Other possibilities might be the age of the tree, and extreme temperatures, such as cold, which may kill the buds.

I would suggest continuing to water and see if it flowers again next season.

There is some discussion about dogwoods failing to flower on the forum of University of British Columbia Botanical Garden. Possible reasons include the age of the tree (not applicable in your case), excessive use of fertilizer, cold damage to buds, lack of sun, and more.

The book 1000 Gardening Questions & Answers (The New York Times) has a section entitled, "Why Won't It Bloom." Reasons that dogwood may not flower are similar to those described above:

    1. Overfertilizing - creates excessive foliage
    2. Excessive Shade - need at least 4 to 5 hours a day and more sun means more flowers
    3. Frosts or droughts - at the wrong time (Dogwoods need lots of moisture and we have had several years of drought)
    4. Pruning - removing the flower buds unintentionally

Season All Season
Date 2008-01-24
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Keywords: Cornus florida, Trees--Diseases and pests, Master gardeners

PAL Question:

I have a couple of dogwood trees, both are about 40 years old. In the front yard is a pink dogwood approx 25 ft tall and in the backyard a white one, approx 50 ft tall. Each year in the spring for the past few years the leaves have been browning and falling off the white one. Now the pink one is beginning to develop the same symptoms. Is there anything I can do?

View Answer:

Thank you for your question about Dogwoods. There are several possible causes of leaf drop in Dogwoods. Below, please find referral information for the Master Gardeners and two websites that contain information about pests and diseases of Dogwoods and methods used to control them.

To know for sure what is causing leaf drop in your trees, you may wish to consider bringing a bagged sample of the leaves to the Master Gardeners Diagnostic Clinic here at the Center for Urban Horticulture or another of the many Clinic locations. For Clinic locations and hours in your area, please go to the King County Cooperative Extension website and scroll down to the Seattle Clinics section. Here is the web address: http://king.wsu.edu/gardening/PlantClinics.html.

The University of Maryland Cooperative Extension Integrated Pest Management Series on Dogwoods offers an extensive list of pests and diseases that prey on Dogwoods. Go to http://plantdiagnostics.umd.edu/index.cfm and search for "Dogwood." The page includes pictures as well.

You mentioned that the leaves of your trees turn brown and then drop. These symptoms are commonly found when Dogwoods have been attacked by Anthracnose. The Washington State University Cooperative Extensionís "Dogwood Anthracnose" page may be of use in helping you determine whether your trees have this disease.

Hopefully, this information will get you started. If you would like more information or have any other questions, please be sure and let us know.

I hope that your trees recover!

Season Spring
Date 2008-01-31
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June 24 2013 12:55:25