Posts tagged invasive

Your questions: tree talk

Readers have trees on their minds this month.

Dale, who lives in southeastern Wisconsin, submitted the following question: I have a beautiful Walnut tree but it has been sprouting branches near its
bottom and just does not look right.  Can I prune them now ? If so what angle? And should I put something on the exposed ends? Some of the branches are approx. an inch in diameter. I surely don’t want to harm my tree!

Teresa submitted the following: I am in need of help to get rid of the seedlings from my pear tree. I need to know when and how to manage them as I have a flowerbed under my tree. I did not put these in but inherited them from the previous owner. They are a nightmare to deal with. Thank you for your help.

If you have advice for Dale or Teresa, leave a comment below.

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Five Master Gardens

    Darrell and Joanne Hennessey turned a former cow pasture into a breathtaking landscape. Their home in Marion is one of five on the Linn County Master Gardeners Garden Walk, set for 10 a.m. to 3 p.m. Saturday, June 13, 2009. The walk was canceled last year due to the flood.        Darrell said the couple battled hip-high weeds and grass when they built their home nearly 20 years ago. Invasive multiflora rose had to be cut out constantly. “It was kind of an uphill battle for awhile,” he said. They still battle deer, with 5-foot-tall plastic snow fence used to protect dwarf conifer and arborvitae in the winter. Soaker hoses are barely visible inside the beds and tags mark most of the plants, so identification is easy.

   The acreage is the kind of place where you could spend hours looking at the various flower beds that Darrell has constructed. He’s been spending four to eight hours daily getting ready for Saturday’s garden walk. If you get the chance, check out the Hennessey gardens and others on the tour.    I wish we could have visited all five of the gardens. They all sound marvelous.  More info and photos are in the Sunday, June 7, issue of The Gazette, and online at:

      I didn’t get to stay nearly as long as I would have liked, but here is some of what I saw last week when I visited the Hennessey gardens:   






Several of the conifers at the Hennessey gardens/ Cindy Hadish photo

Several of the conifers at the Hennessey gardens/ Cindy Hadish photos





Darrell Hennessey takes a break from edging his garden beds to point out a feature of one of his dwarf conifers

Darrell Hennessey takes a break from edging his garden beds to point out a feature of one of his dwarf conifers

Hosta bed and trees at the Hennesseys' Marion acreage

Hosta bed and trees at the Hennesseys' Marion acreage

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Invasive species alert!

Callery pear photo by New Invaders Watch List
Callery pear photo by New Invaders Watch List


 Cedar Rapids City Arborist Daniel Gibbons wants residents to be aware of an invasive species that could become a problem soon in Iowa. The ornamental Callery pear is a popular urban landscape tree, valued for its white flowers.  But Gibbons, who served as horticulturist in Columbia, Mo., and has held his Cedar Rapids post since January, warned that as the trees age, hybridizing starts. The wild seedlings, which produce thorns and have weak branches, can grow in the sun, shade, or anywhere and overtake prairies and other native areas. Birds that eat the berries spread the seeds.

    While Gibbons has not heard of the wild version growing in this area yet, he noted that education is important. “In order for it not to happen, the word needs to get out,” he said. “Education may save us.”

      Here is more on this invasive species, from the Cedar Rapids Public Works Department:

 The introduction of exotic plant and tree species for the purpose of aesthetic gardens or utilitarian roles has been practiced within the fields of horticulture and forestry since ancient times.  Our tendency to become dissatisfied with native flora all too often cultivates a desire to expand our landscape pallet to non-native varieties and cultivars.  Such new specimens can produce vivid floral or textural displays, offering an arboretum or landscape renewed appeal. 

 Unfortunately, the cost of promoting newly discovered species that are out of place in our native ecosystem is rarely known until years after introduction.  Much of the time there are minimal impacts to the native ecosystem from well contained non-native landscapes.  Occasionally however, a plant or tree can escape and pose enormous consequences to native plant communities.

 Pyrus calleryana, is one such exotic species that has “escaped”.  Ornamental (Callery) pear trees have been prized for their tidy form and magnificent spring display of snow white flowers.  Although now known to be weak-wooded and prone to storm damage, Callery pear cultivars such as ‘Redspire’, ‘Bradford’, ‘Capital’, ‘Cleveland Select’ and others are foundational to many landscapes because of their sure establishment and nearly pest free acclaim.

 Although earlier thought to be sterile and unable to reproduce, wild hybrids are now sprouting up across the country where landscape pear plantings have matured.  These new pear hybrids are not only thorny, but also have retained the weak branching structure of the parent cultivars.  Hybrids from nursery produced trees are also extremely vigorous, and seem to tolerate numerous site conditions, eventually producing a thorn-filled stand of trees too thick for native regeneration. This spread may prove to be one of the most serious problems to date for land managers and home owners alike.

 Within our neighboring state of Missouri, Columbia Park Natural Resource Supervisor Brett O’Brien successfully partnered with the Missouri Department of Conservation and the Missouri Community Forestry Council to form an educational program called, “Stop the Spread!”  In 2002, the Columbia Parks Department began noticing wild pear trees growing in a natural area.  Within 6 years, thorny hybrid pear trees are now abundant and increasing within Columbia utility right-of-ways, natural areas, and even well-maintained park landscapes.

 According to an article by Theresa Culley and Nicole Hardiman in Bioscience (December 2007 / Vol. 57 No. 11), Callery pear cultivars are now listed by 6 eastern states as invasive, with more to come.  Culley/Hardiman note that pear hybrids spread rapidly within restored prairie wetlands and are capable of producing “impenetrable” thorny thickets.

 As ornamental pear populations increase from landscape plantings within our region, the danger for cross-pollination and the production of wild pear hybrids will increase.  The importance of developing awareness to this problem and reduction of market demand for ornamental pear trees is critical.  Homeowners, developers, nursery growers, and municipal forestry departments share the responsibility to promote the use of alternative species as substitutes for the Callery pear.  Without such cooperation, Central Iowa could soon face the costly and ecologically devastating effects of hybrid pear colonization now being realized elsewhere.

 Pictures are available at under City News.  Click on the Invasive Species Alert link to view the PDF file.








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