Core Viewpoint - The article discusses the delayed color change of autumn leaves in Beijing, attributed to unfavorable weather conditions and plant diseases, with a notable improvement observed by the end of October [1][5][6]. Group 1: Weather Conditions - The optimal conditions for leaf color change include low temperatures and strong sunlight, which were lacking earlier in the season due to high temperatures and prolonged rainy weather [6][7]. - As of October 31, the weather began to clear, providing favorable conditions for the leaves to change color [6][10]. Group 2: Leaf Color Change Timing - The best viewing period for red leaves in Beijing is projected to be from late October to mid-November, with a one-week delay in color change compared to previous years [5][10]. - The peak viewing period for the iconic Fragrant Hills is from October 25 to November 15, with an expected 80% color change in certain tree species [5][10]. Group 3: Plant Health Issues - Observations indicate that some yellow leaves appear unhealthy, potentially due to two main diseases: powdery mildew and wilt disease, which affect the health and color of the leaves [9][10]. - The wilt disease is caused by a soil-borne fungus that has persisted in the soil for years, affecting the newly planted trees in Beijing [9][10]. Group 4: Diversity of Autumn Foliage - The article highlights that autumn foliage in Beijing is not limited to red leaves; various colors such as yellow, brown, and purple are also present, showcasing a rich diversity of plant species [10][12]. - Parks like the Olympic Forest Park and others feature a variety of colorful leaves, including ginkgo and white wax trees, contributing to the vibrant autumn scenery [12][13].

Group 1 - The core point of the article highlights the delayed blooming of osmanthus flowers in regions like Shanghai and Zhejiang due to higher than usual temperatures this year, with blooms occurring over 20 days later than last year [3][7][10] - In Shanghai's Qingpu District, the first signs of osmanthus flowers are noted, with a subtle fragrance in the air, indicating the beginning of the blooming season [1] - In Hangzhou, the osmanthus flowers have just started to bloom, with most still in bud form, but conditions are expected to improve for a fuller bloom in the coming weeks [4][7] Group 2 - The article discusses the sensitivity of osmanthus flowers to temperature and humidity, noting that they typically require temperatures below 24°C to bloom effectively [8] - In Hefei, osmanthus flowers are experiencing a second bloom due to a recent drop in temperature, which has allowed previously interrupted blooms to resume [11][13] - The article also mentions the optimal viewing periods for other natural phenomena, such as the autumn foliage in Hebei and the golden poplar trees in Ningxia, indicating a broader seasonal trend in nature [14][19]