Thousand Cankers Disease of Walnut Close to DE

August 14, 2012 under Cooperative Extension

TCD on black walnut – image courtesy of Karen Snover-Clift, Cornell University

Thousand Cankers Disease (TCD) of black walnut was found in central Virginia along I-95 in 2011, and later that year in Bucks County, PA. TCD is a disease of walnut trees, Juglans spp., and it has continued to spread east in the last few years, after initial finds in the Western U.S. and Tennessee. The causal fungus is carried by the very tiny walnut twig beetle. Small cankers form under the bark of the tree, and ultimately trees die. Yellowing and dieback in the tops of trees are usually the first symptoms. Native black walnuts in Delaware are at risk.

Contact the UD Plant Diagnostic Clinic for information.151 Townsend Hall, 531 South College Avenue, Newark, DE. (302) 831-1390.

Click here for a fact sheet about the disease.



Botanic Gardens tour highlights flowering magnolias

March 23, 2011 under CANR News, Events

Magnolias will be featured on the University of Delaware Botanic Gardens tour and at the annual plant sale.

When John Frett leads a guided walk of the University of Delaware Botanic Gardens on March 31, he’s hoping to point out a few early blooming magnolias. More likely, though, he’ll head to the greenhouse to show off magnolias in flower.

Non-native magnolias typically start blooming in Delaware in April while the native varieties wait until May.

With plenty of other March blooms to enjoy — winterhazel, forsythia, hellebores and some dogwoods — why the rush to spot magnolias?

The walk is a spring tradition that highlights plants available at the UD Botanic Gardens Plant Sale. Along with winterhazel, magnolias will be a featured plant of this year’s sale, which is open to the public April 29-30.

Almost everyone loves magnolias. Frett, the director of the UD Botanic Gardens, is no exception. However, he’s reluctant to single out a best-loved cultivar or species. “It’s like picking a favorite child, they’re all fabulous,” says Frett.

Magnolias vary widely. The 80 or so recognized species include trees and shrubs; deciduous plants and evergreens; cold-hardy varieties that do well in Maine and others that flourish in the tropics. About the only thing they have in common are the distinctive, tulip-shaped flowers. And most — but not all — are highly fragrant.

Under Frett’s leadership, the magnolia collection at the UD Botanic Gardens has been expanded to 100 taxa of magnolia, with some 125 magnolias in all.

“The UDBG’s fantastic collection of magnolias includes a nice variety of native and non-native species and cultivars,” says Sue Barton, Cooperative Extension’s ornamental horticulture specialist.

Magnolias are widely scattered throughout the UD gardens but large groupings can be found between Townsend and Worrilow Halls, south of Townsend, and also north of UD’s outdoor pool.

In assembling the collection, Frett looked for a progression of flowering, from the earliest species, in April, to varieties that are still going strong in June. He also included rich and unusual colors, found in the hybrid varieties. In addition to characteristic pink or white petals, magnolia blooms can be light to medium purple, deep purple that is almost red, and yellow.

Barton has one of the yellow varieties in her backyard. “I bought the ‘Elizabeth’ cultivar from the UDBG sale a number of years ago because my older daughter is named Elizabeth,” she explains. “This tree will be covered with yellow flowers in about a month.”

Despite its name, “Elizabeth” isn’t Barton’s favorite backyard magnolia. That distinction goes to the native sweetbay magnolias growing near her patio. “They’re multi-stemmed so they help enclose the patio but you can still view through them so they don’t make it claustrophobic,” she says.

Carrie Murphy, the Extension horticulture agent for New Castle County, says the sweetbay is the top pick for most Delaware gardeners. “Including me,” she adds.

“The sweetbay magnolia is by far one of my favorite plants — it has beautiful late spring and early summer blooms and is lightly fragrant.”

But what Murphy really likes about the sweetbay isn’t apparent at first glance. “I love the underside of the foliage — when the wind blows and rustles the leaves, the silver underside of the leaves becomes visible and it’s absolutely gorgeous,” she says.

Several sweetbays have been added to the Master Garden Demonstration garden at the county Extension office in Newark. At the demo garden, home gardeners often ask for recommendations for small flowering trees and sweetbay nicely fits the bill. It prefers moist soil and some shade and even works well in wet sites. But it’s also adaptable to drier conditions, says Murphy.

Three cultivars of sweetbay will be available at the plant sale: “Mardi Gras,” with a butter-yellow variegated leaf; “Perry Paige,” a new dwarf variety only five to eight feet tall; and “Green Shadow,” a selection that Frett describes as “nearly an evergreen.”

Two other native magnolias will be sold, Magnolia macrophylla “Big Leaf Magnolia,” featuring huge leaves with a tropical feel and Magnolia pyramidata “Pyramid Magnolia,” which is considered rare. Also available will be three hybrids from native species, including two that originated from a cross with the native cucumber tree.

Guided walk

March 31: An hour-and-a-half walk through the UD Botanic Gardens, focusing on plant sale selections. 4 p.m. $5. Call 302-831-2531 or email [] to register. Maximum 35 people.

UDBG plant sale

Public sale hours are 3-7 p.m., April 29; 9:30 a.m. to 4 p.m., April 30. For more information, call 302-831-2531 or go to the UDBG website.

Article by Margo McDonough
Photos by Danielle Quigley

This article can also be read online on UDaily by clicking here.


Fall Foliage on Campus is Spectacular

October 19, 2010 under CANR News, Cooperative Extension

Blue and gold aren’t the only colors at the University of Delaware. This time of year, the campus is ablaze in fall foliage. The American elms on The Green become a soft yellow, the maples at Trabant Student Center turn crimson, the serviceberry trees at the Fred Rust Ice Arena display orange leaves and the gingkos on South College Avenue become a luminous, clear yellow.

“The fall landscape is spectacular on the campus,” says Susan Barton, UD Cooperative Extension‘s specialist for ornamental horticulture. “When it comes to autumn color, I believe the campus and the entire state are every bit as beautiful as other regions I’ve traveled to during the fall foliage period.”

This week — the third week of October — tends to be the peak time for foliage in Delaware. The summer’s intense heat and drought conditions shouldn’t significantly impact the “wow factor” of the foliage, according to Barton.

“During the heat wave, some trees experienced leaf drop or brown, withered leaves and they obviously won’t be looking good this fall. But for the majority of the trees that didn’t suffer from heat it was actually mid-September to mid-October that was critical in determining the quality of the foliage now,” says Barton.

The process of leaf change gets under way at the time of the autumn equinox, she says. During the summer growing season, leaves look green due to the presence of chlorophyll, which masks the other pigment colors. With the arrival of the autumn equinox and the start of longer nights and shorter days, chlorophyll production in the leaves slows, and soon other pigments become more visible.

Sunny days and cool nights around the time of the equinox deliver the most dramatic fall color.

Purple and red pigments in the leaves need the breakdown of sugar that occurs on bright autumn days, explains Barton. Cool temperatures at night break down chlorophyll, allowing the yellows and oranges to show. However, too cool isn’t good, as an early frost kills the leaf cells and reduces the coloration process.

Too much rain in late September and early October, especially coupled with warm conditions, can make for less-than-brilliant color at foliage time. Delaware received a lot of rain in a short period earlier in the month – 7 inches was recorded in Newark on Oct. 1 – but that shouldn’t impact the foliage.

“That rain wasn’t that unusual — except for one day — it was just concentrated after a long period without rain,” says Barton. “If you counted up all the rainy days in the fall, we haven’t had that many yet.”

A variety of other factors have an impact on foliage coloration, including plant genetics and soil conditions (such as the pH and the availability of trace minerals), she says.

Barton gets to enjoy great fall color not only during her workday at UD but also at her 7-acre property, where she’s planted many natives that are known for fall color. Some of her favorites are sourwood, which turns brilliant red, and fothergilla, a shrub that has multi-colored leaves.

“Out of all the fall colors and hues, orange is my favorite,” she says. “I love orange sassafras, serviceberry and sugar maple. Even better, though, are sweet gum trees because they have orange color plus yellow and purple, all on the same tree.”

Barton has planted serviceberry behind a low retaining wall at her home and is looking forward to enjoying its bright orange display. But she’ll need to drink in the view quickly – serviceberry only stays orange for a few days before dropping its leaves.

Most native American plants are speedier than their European counterparts at transitioning from fall to winter, she says.

“In Edgar Anderson’s book Plants, Man and Life he notes that our native flora evolved for our ‘violent American climate,’” says Barton. “He describes it as ‘going into the winter condition with a bang.’”

Sounds like it’s time to get outside before the fall fireworks are over.

Article by Margo McDonough

Read this article on UDaily by clicking here.