Twice-Yearly Blooming of Chestnut Trees in Kyiv Linked to Leaf Miner Stress

Unusual Autumn Blossoms on Kyiv’s Chestnut Trees

According to Рубрика — Суспільство: In Kyiv, chestnut trees are experiencing an uncommon second flowering during the autumn months. This phenomenon is caused by the chestnut leaf miner, an invasive pest originally from Macedonia. The infestation leads to early leaf drop, which puts the trees under stress similar to winter dormancy. As a result, buds that normally awaken in spring are triggered prematurely, causing the trees to bloom again in the fall.

Normally, chestnut leaves remain green through September to store nutrients for the winter. However, the damage inflicted by the leaf miner causes leaves to fall early, weakening the trees and making them more susceptible to diseases. Following this leaf loss, warm and humid weather conditions encourage a second blooming cycle.

Yuriy Klymenko explains: “The plant behaves as if spring has arrived. With warm temperatures and rainfall, it starts to wake up and produce flowers.”

Combating the Chestnut Leaf Miner

Experts employ several strategies to control this damaging pest, including:

• Collecting and composting fallen infected leaves;
• Applying chemical treatments to the trees.

Applying chemicals during the growing season poses risks to public health, so an innovative approach has been developed where treatments are injected directly into the tree trunks (grafting method).

Yuriy Klymenko notes: “We inject the treatment and monitor whether cavities form over the following years, which could make the trees hazardous. This is a theoretical risk; it may not occur, but it must be observed. So far, this remains the most effective method.”

The injected treatment remains active for about two years. Treated chestnuts are found not only in the M. M. Hryshko National Botanical Garden but throughout Kyiv. This procedure is costly and requires ongoing monitoring of the trees’ health after injection. Since the chestnut tree is a cherished symbol of Kyiv, maintaining its vitality is crucial not only for the city’s ecology but also for its visual character.

This chestnut leaf miner issue highlights broader challenges posed by climate change and invasive species affecting urban ecosystems. The pest threatens both the health of the trees and the overall appearance of Kyiv’s green spaces. Developing and refining treatment techniques will be essential to preserving chestnuts as a symbol of the city and maintaining ecological balance.

In light of the challenges posed by the chestnut leaf miner, the city is also implementing a comprehensive strategy to safeguard its cherished chestnut trees. This proactive approach aims to address the vulnerabilities of these iconic trees and ensure their longevity amidst increasing environmental stressors.