Posts tagged oak wilt

California Dreamin’ – tree style

The following is by James Romer, Extension Horticulturist at Iowa State University:

   This time of the year gives many gardeners an empty feeling. It is hard to keep warm and dry when temperatures dip below zero and it snows every other day. It is reminiscent of those classic song lyrics — “All the leaves are brown and the sky is gray … California dreamin’ ….” Anyway, this is a great time of the year to do some planning and pruning.

   The late dormant period (February to early April) is an excellent time to prune deciduous trees. The absence of foliage at this time of year gives the home gardener a clear view of the tree and allows him/her to select and remove appropriate branches.              

   Proper pruning improves the appearance, maintains the health and prolongs the life of trees. Improper pruning destroys their natural beauty, weakens them and may lead to their premature death.

   It is essential to make proper cuts when pruning trees. Do not make flush cuts. Flush cuts are cuts made as close as possible to the trunk or main branch. Flush cuts produce large wounds, destroy the tree’s natural mechanisms that promote healing and slow the “healing” process.

    When pruning trees, make the final cut just beyond the branch collar and branch bark ridge. The branch collar is the swollen area at the base of the branch. The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk. Pruning just beyond the branch collar and branch bark ridge retains the tree’s natural defense mechanisms and promotes the healing process. When a branch is pruned properly, a slightly raised area remains on the trunk or main branch. However, do not leave stubs.

   Do not apply wound dressings to pruning cuts. The application of wound dressings or paints doesn’t stop decay and may actually inhibit or delay the healing of wounds.

   There is one exception with not applying paint to oak trees. Oak wilt is a fungal disease that is lethal to many oaks. Oak wilt infections occur most commonly in spring and early summer and are spread from infected trees to healthy trees by sap-feeding beetles. To reduce the risk of the spread of oak wilt, don’t prune oaks from April 1 to July 1. If oak trees must be pruned between April 1 and July 1, for example, to correct storm damage, immediately apply a latex paint to all cut surfaces to avoid attracting sap-feeding beetles to the wounds.

   Use the three-cut procedure when cutting large branches to prevent extensive bark damage. Make the first cut about one to two feet from the main branch or trunk. Cut upward and go about halfway through the branch. Make the second cut a few inches beyond the first. Cut downward completely through the branch. Make the final cut just beyond the branch collar.

   Some trees, such as maple, birch and elm, bleed heavily when pruned in late winter or early spring. However, the heavy bleeding doesn’t harm the trees. (The trees won’t bleed to death.) Eventually the flow of sap will slow and stop. Heavy bleeding of susceptible trees can be avoided by pruning in late June or early July.

   The pruning of deciduous trees by the home gardener should be limited to small trees and the removal of smaller branches that can be reached from the ground in medium to large trees. Branches high up in large trees and those near utility lines should be left to professional arborists. Professional arborists should have the proper training and equipment to safely perform the job.

    If that’s not enough to do, another enjoyable winter activity is to leaf through garden catalogs. Many contain colorful plant photographs. Some carry specific merchandise, such as seeds, perennials, roses or fruits. Others carry a wide variety of products.

    Also, visit a bookstore or public library and browse through some of their gardening books. Excellent reference books for home gardeners include “Manual of Woody Landscape Plants” by Michael Dirr; “Continuous Bloom” by Pam Duthie; “Herbaceous Perennial Plants” by Allan Armitage, and many others.    

    Remember also that your Iowa State University Extension county office has numerous publications on gardening in Iowa. Most of these publications also are available from the ISU Extension Online Store at www.extension.iastate.edu/store.

So get busy planning, pruning and dreaming about plants for this spring.

 

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November need-to-know

Linn County Master Gardener, Susan Long, prepared the following Q & A’s that are frequently asked of Hortline volunteers in November.

                Q:  Can I plant potted mums in my garden now for blooms next year?

                A:  Even though potted garden mums may be deemed “hardy”, they don’t over-winter well in Iowa.  The repeated freezing and thawing may heave the plants out of the ground causing damage or death.  The best protection is to not cut back any of the plant and mulch heavily with clean straw, pine needles, or evergreen branches after several hard freezes (mid to late November).  Leaves tend to mat down and don’t serve as adequate protection.  Spring is a better time to plant mums as they have the summer to establish themselves.

 

                Q:  Is it OK to prune oak trees now?

                A:  Winter (December through February) is the best time to prune oak trees in Iowa.  Pruning oak trees in winter greatly reduces the risk of an oak wilt infection.  Oak wilt is a fungal disease that is lethal to many Oaks.  It can be spread from infected trees to healthy trees by sap-feeding beetles.  Oak wilt infections occur most commonly in spring and early summer.  Pruning oak trees in winter greatly reduces the risk of an oak wilt infection as the beetles and fungal mats are not present at that time of the year.

 

                Q:  How do I get my Christmas cactus to bloom at Christmas?

                A:  Day length and temperature control the flowering of a Christmas cactus. Temperatures shouldn’t be above 70’ in the daytime with nighttime temperatures of 60-65’.   Provide your plants with bright day light, not artificial light, until mid-October.  Move the plant to an unused location after mid-October, giving your plant 14 to 16 hours of continuous darkness each day for at least 3 weeks.  Keep the soil conditions dry, watering every 7-10 days.  They don’t like to be moved, however, once buds set the plant can be moved to another location.  Your plant should start to bloom at Christmas.

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Oak Wilt Alert

The following is from Master Gardener Gene Frye about the revised “no prune” period for Iowa oak trees: 

  ISU Extension Foresters have just expanded the recommended “no-prune” period for Iowa oak trees to extend from March 1 through October 31 in order to minimize the chances of contracting the oak wilt disease.  The previous recommendation for not pruning was from mid-March through August.

 Oak wilt, a fungus disease, is fatal to all oaks in the red oak family within one year of the onset of the first symptoms, but white oaks may live for several years, and some even recover from the disease, but with substantial damage. 

 The main method of contracting oak wilt is through pruning or other wounds made during the growing season, with the resulting sap attracting certain insects carrying the oak wilt fungus on their bodies.  These insects bore into the wound carrying the fungus spores with them. 

 The other method of spreading oak wilt is through root grafts of nearby oaks of the same species.  Root grafts allow trees to exchange body fluids, so to speak.  Since the roots of most trees extend out to about the height of the tree, trees nearer than about one hundred feet of an infected tree of the same species can also acquire the disease.  Red oaks will not root graft with white oaks. 

If oaks must be pruned during the no-prune period, for example to manage storm damage, the pruning wounds should immediately be covered with a mixture of an outside white latex paint diluted one-to-one with water.  This is one of the few circumstances in which Extension Foresters recommend use of wound dressings.

 The first symptoms of oak wilt are a general drying and falling of leaves, usually during June or July.  In the case of red oaks, the whole tree is usually affected, but on white oaks, only individual branches show symptoms the first year of infection, followed the next years by more branches being affected.

  Positive diagnosis of oak wilt requires a laboratory test, but a reasonably reliable diagnosis can be made by finding longitudinal brown streaks just underneath the bark on affected branches.  Unfortunately, there are several other ailments that can appear to be oak wilt. Oak wilt usually appears in clumps, and is not nearly as devastating as chestnut blight or Dutch elm disease.  Infestations can usually be contained by application of good management practices. 

For more detailed information on oak wilt, see Extension publication SUL 15, “Oak Wilt—Identification and Management,” which is available at County Extension Offices for $1.00 or can be downloaded free of charge on the Internet at:  www.extension.iastate.edu/store  

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