Why Does My London Planetree Drop It’s Leaves In The Summer?

69747689.I2pKj23U Why Does My London Planetree Drop It’s Leaves In The Summer?

Photo Courtesy of: Hubert J. Steed

London Planetrees are the descendents of both European Sycamores and American Planetrees. They look much like Sycamores, with similar leaves, and showy peeling bark in brown, silver, and green hues.  London Planetrees are commonly planted as street trees currently due to their hearty disposition and disease resistance to anthracnose and some pests.  Ideally they should be planted in areas with plenty of moisture, but in many cases the roadside and “construction grade soil” that they are planted in can cause the tree problems initially, and lead to defoliation in the warm months.

Why is my London Planetree losing leaves?

London Planetrees are very tough, and they can put up with smog, reflected heat, and other common city environmental conditions, and as a result they’ve become very popular in dry and tiny street side beds and newly completed housing areas.  In the summer months many of these trees begin to defoliate gradually until there may be only a tiny handful of leaves left on the trees. The trees begin to look dead or even infected with the anthracnose disease that also causes rapid leaf loss. Anthracnose can occasionally effect Planetrees, but the disease is a cooler weather problem that most often occurs in spring, and tapers off naturally in the heat of the summer.

What happens with London Planetrees in warmer weather is most often a natural defoliation process that the tree goes through when it is undergoing heat stress.   London Plane’s are one of several types of trees that actually intentionally put out more leaves in the spring than they are “planning” on keeping.  They double the number of leaves they put out the spring to capitalize on the moist, cool, and sunny conditions.  Once the hot and dry weather of summer hits London Planetrees they will slowly dry and drop leaves to save themselves energy, and to have less to support.  This is a kind of lesser hibernation scenario, and the trees will often put out new leaves again in the fall before dropping them again for the winter.

Can I fix this problem?

Additional deep root watering can help your tree retain more leaves, so watering your tree more can help, but may not stop the defoliation process. The defoliation is also dependent on the type of soil around the tree, which in many newly constructed areas is very poor due to the practice of removing topsoil for retail sale prior to building completion.  My experience has been that there is a reduction in the amount of leaves lost by an individual tree after the tree has had a number of years to really build up a good root base – in some places this has taken 10 years before the tree seems to be able to provide for more leaves through the summer.

If you have a London Plaintree that appeared healthy in the spring and early summer that then slowly dropped most of its leaves, examine the tree for pests firstly, and then secondly check for healthy leaf tissue.  Brown or black spots can mean that there is a fungus or a disease, but simple color loss, browning and falling is most often due to simple heat stress.  In the case of heat stress you tree will make a natural recovery, and regain its foliage at a later time.

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  1. Carl says:

    Dear Amy,

    Thank you; this advice is perfect for my use in dealing with a client.
    I knew the answer but to find it elsewhere and written so well has really helped – thank you.

    Imon Site Ltd,

  2. Gary says:

    I planted a London Planetree a few weeks ago and found that my highly alkaline and clay-like soil was retaining a lot of moisture. The ground around the tree was constantly moist, so out of fear of overwatering, I continually checked the moisture and didn’t water it due to the seemingly high moisture. After about two weeks, the leaves started turning yellow. I feared that it was still too moist. After about three weeks, nearly all the leaves had fallen off. The ground around the tree is still moist, but I discovered that the root ball itself was actually quite dry. Now there are no leaves on the tree and I am doing a soak every other day to try and recover the tree. I hope that the leaves only fell off so it could better “focus” on establishing a root system. I’m very worried about it at this point. Your article gives me some hope that it’s ok. Scratching the bark still reveals very green and live tissue, so I hope it recovers. Any advice would be welcome!!

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