American Linden street trees lose popularity due to sticky aphid issue

While it’s hard to see it under all the sticky debris, I’m holding my flip-flop sandal and examining it after walking under an American Linden tree.  I learned a lot about linden aphids from Chamber of Commerce employee Darlene Larsen after walking on a sidewalk near the Chamber building.

Darlene Larsen, a Renton resident who cheerfully assists visitors at the Renton Chamber of Commerce, has brought a sticky situation to the city’s attention.  She recently responded to a request for input on the landscaping plan for the Rainier Avenue reconstruction.  Her input:  please do not plant American Linden street trees.

Ms. Larsen knows what she’s talking about.  She has kept a washtub handy at the Renton Chamber of Commerce this summer to help visitors clean their shoes if they walked through the sticky mess on the sidewalk on the north side of the Chamber building.  Some heritage-size American Linden trees shade the sidewalk and street parking along this section of South 4th Street, and these stately, dark green trees were historically ideal street trees.  Regrettably, the invasive linden aphid has recently been attacking these trees,  and while the trees are hearty enough to survive the attack, the aphids produce a very sticky byproduct that gets all over sidewalks, cars, signs, hydrants, and shoes.  The sticky substance is called aphid honeydew, and it clings like syrup to everything it touches.

Ms. Larsen kindly goes out of her way to help visitors clean the aphid honeydew off their shoes

When the city asked that public comments be sent to the Rainier Construction team regarding the Rainier Ave landscape plan, Ms. Larsen noticed the draft plan appeared to potentially include Linden trees.  So she made an input today (September 13), that included the following recommendation:

“From our experience with city trees at the chamber, I would like to highly recommend you not plant these anywhere in Renton.  These trees, while visually beautiful are a continual maintenance horror, and public nuisance. For 3 months of the year, everything that lies under them is subject to a layer of sticky ‘dew’ from aphid droppings. This dew, and the ‘pre-dropping leaves’ create a horrible mess on roofs, landscape, cars, the sidewalks and when people are walking by, it builds up on their shoes. The only way to remove it is by soaking in water. This also becomes a hazard to people that try to walk in the street to avoid the area, or completely cross the street to walk on the other side to avoid the areas. ”

She goes on to explain that the costs of cleaning the aphid honeydew off of sidewalks on a regular basis is a significant burden for businesses and nonprofits like the Chamber, and she would like to spare others from this burden.

A leaf blower won’t work to gather the summer fallen leaves under a Linden tree during aphid attack. The dripping honeydew aheres the leaves to the sidewalk until a pressure washer can be employed. (This and other photos in this article were shot on July 17, 2023,  by Randy Corman)

Aphid honeydew covers the trees lower leaves, and the sticky leaves catch fallen upper leaves

This car’s tires show evidence of rolling through the linden aphid honeydew. Cars parking under the tree for any length of time need a bath.

This American Linden trees in front of the Chamber of Commerce are part of an official Renton Tree Tour, and everyone would like to stop the aphid attack on them. Unfortunately there are not any practical ways to do so without using chemicals that endanger beneficial species like honey bees which are highly attracted to these trees.

Even under attack by aphids, Linden trees are impressive for their heavy foliage and large size.  This also makes them difficult to treat chemically even if safe chemicals could be found.