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Garden Q&A: Rust on serviceberry trees is common with cool, wet weather

For The Baltimore Sun

My serviceberry trees produced normal fruit initially, but then developed orange-colored spikes all over the fruits. Some leaves turned yellow and rust-colored with spots. Also, there are tubular deformed protrusions on branches. I think this is rust. Red cedars are 15-20 feet away. Should these be removed since they are the alternate host of the rust disease?

The rust on serviceberry (Amelanchier) is disfiguring but will not kill the plant. It can be common in years with cool, wet weather, and we are getting a lot of reports. Yes, the rust needs to spend part of its life cycle on its alternate host such as junipers, including Eastern red cedars (Juniperus virginiana), Common juniper (J. communis) and Creeping juniper (J. horizontalis). However, removing the junipers is unlikely to halt the problem, because rust spores can travel several miles and there will undoubtedly be other junipers in your area. Rust is very weather-dependent, and you may not have a problem next year. Search “rust” on the HGIC website. No chemical control is recommended for rust on ornamental plants.

In my city rooftop garden, I have a pumpkin patch in a big raised bed. The vines are growing like crazy! I’ve had hundreds of male flowers, but only three female flowers have made pumpkins so far. The rest turn yellow, shrivel and die before they grow beyond the size of a marble. It’s so discouraging. I need your advice.

This sounds like a pollination issue. There may be a lack of bees up on the rooftops. Consider hand-pollinating the pumpkin flowers. You can do it with a soft bristle brush, but with the many male flowers you have, you can just use a male flower directly. There are good videos on hand pollination online. Search “pumpkins” on the HGIC website.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at Click “Ask Maryland’s Gardening Experts” to send questions and photos.

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