Most can fend for themselves, but some, such as acacias and Texas oaks, owing to the relative weight and density of their leaves and the weakness of their trunks, require a helping hand from man.
正常的樹，樹根約與樹冠同寬，很自然地就能站得穩；只有少數如橡皮樹、黃槐，因葉子厚、重、樹幹不夠粗大，根系先天無法長得和樹冠一樣好，得靠人力略為修剪。為什麼我們的路樹會「頭重腳輕」？