Lal said:”That is a brief introduction. This is a topic to be discussed in more detail. For example, some people question the practice of “worshipping” Bo trees, stupas, or statues of the Buddha”.
About the stupa, i read something in DN16§5.11 (translation Walshe)
-“A stupa should be erected at the crossroads for the Tathagata. And whoever lays wreaths or puts sweet perfumes and colours there with a devout heart, will reap benefit and happiness for a long time”.