Bloom Where You Are Planted

Our monthly Bloom Where You Are Planted articles offer seasonal inspiration and guidance from experts about trees and plants, animals and bugs, City water quality, stormwater management, and the beautiful green space that sustains the Wissahickon watershed.

May Tree of the Month

What’s ailing our sycamores and London planetrees? I have received many questions this spring about what is causing the young leaves of sycamores and Planetrees to wither and drop prematurely. This is so prevalent on some trees that they were heavily defoliated by mid-May.

This problem is caused by a fungal disease commonly known as anthracnose. It is most common when there is a prolonged cool (average temperature below 55F) and a wet period in early spring. These conditions, where the foliage remains continuously wet,  allow the fungal spores to successfully germinate and grow on the very young, emerging leaves and branchlets. These spores are released from the old leaves and fallen twigs on the ground. A few weeks later, dead patches on the leaves appear, or whole young branches may die back. This is sometimes followed by a cluster of small branches arising from a single point called a witches broom. This disease may weaken the tree but is usually not fatal, and the tree will soon produce healthy new growth. By summer, most trees will recover. London planetrees (Platanus anthracnose)

Sycamores and London planetrees are tough, stress-tolerant trees and are among the most widely planted urban trees in the temperate world. The American sycamore (Platanus occidentalis) is native to eastern and central North America, typically growing along rivers and streams in the floodplain. It is distinguished by its dramatic white-mottled bark. The London planetree is a hybrid of the American sycamore and the oriental planetree (Platanus orientalis). It is native to Eastern Europe and the Near East, populating a similar riparian habitat.  But most important, Oriental planetree tends to be highly resistant to anthracnose. The London planetree (Platanus x acerifolia) is a hybrid of the two and usually carries the trait of anthracnose resistance.  A number of clones of London planetree have been selected for form, vigor, and disease resistance. These include ‘Columbia’ and ‘Liberty.’ ‘Bloodgood,’ and ‘Exclamation.’ When planting planetrees, be sure to plant a resistant cultivar.

All photos by Paul Meyer.

If you already have an infested tree, there is not much you can do to “cure” the problem. It will generally correct itself in a few weeks. Do what you can, however, to reduce stress and keep the tree in good vigor. If it is dry, water deeply once a week and fertilize lightly.  In the autumn, collect and remove the infected fallen leaves and branches, as they are a source of inoculum in the following spring. Some symptoms can be observed every year, but periodic cool, wet springs like this year’s lead to more severe disease outbreaks.

Discovering Chestnut Hill

Thank you for joining us on our walking tours on Saturday, April 23, with George McNeely and again on Saturday, May 6, with Rob Fleming.

Springing Into Action

The Conservancy’s many passionate volunteers provide invaluable support and services that help drive our success.

Iconic Architectural Heritage

On Saturday, May 13, George McNeely led a walking tour of the West Side of Chestnut Hill with the Institute of Classical Architecture and Art, focusing on the development of the West Side by businessman and philanthropist Henry Howard Houston and son-in-law George Woodward.

Shortly after, on Tuesday, May 16, architect and city planner Richard Bartholomew led a walking tour group from the International Women’s Club of Philadelphia. The tour highlighted the development of Wissahickon Heights, Pastorius Park, unusual twin house designs (more fraternal than identical!), and many of the community’s iconic classical and modern houses, including the Vanna Venturi House pictured above.

Chestnut Hill continues its distinctive architectural excellence today by preserving the built heritage and conserving open space. This is largely thanks to forward-thinking city planners, architects, designers, and today’s experts who work with community advocacy groups to make the Chestnut Hill community a great public destination that’s already home to a beautiful existing community.

Below are a few Iris and Allium blooms from the walking tour on May 16.

Upcoming Events

Now through May 31, enjoy some of these local community events.

• The Chestnut Hill Conservancy’s Silent Auction opened on May 22
• WeConservePA’s online The Mechanics of Land and Easement Acquisitions webinar on May 23
• Friends of the Wissahickon’s last day to register for the Wissahickon Trail Classic is on May 24
• The Friends of the Tanner House is hosting a fundraiser for Community Cultural Organizing & Heritage Preservation on May 25
• Friends of the Wissahickon’s The Wissahickon in May with Andi Wingert, Debbie Hoellein, and Jim McClory on May 26

Support Our Work

Join the Conservancy or renew your membership to access all your exclusive benefits. For less than $1 a week, anyone can join the Chestnut Hill Conservancy and help sustain the open space, history, and architecture that define this beloved community. Please also consider making a gift anytime throughout the year to support our ongoing work in the community.

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