Recent research shows that plants, including trees, can emit ultrasonic sounds when stressed, such as during dehydration or damage. These high frequency clicks, caused by cavitation in their vascular system, are inaudible to Hardiness Zones Explained: What the Numbers Mean and How to Find Your Growing Zone GoBuyPlants Neem Oil Fact Sheet Is this a Red Anderson? Same plant different lighting on the photos : r RareHouseplants