What is the ruling on using ornaments that are in the shape of a cross, which are said to be originally plant-based, and is the Christians' belief that God created the cross in trees linked to what Umar (may Allah be pleased with him) did with the tree that the polytheists venerated?

Not everything that has an intersection or three leaves is considered a cross with its associated ruling. One must ascertain that the object is indeed a cross and that it was placed as a revered cross by Christians. If this is confirmed, then the cross must be removed, and clothing bearing it should be avoided. A Muslim must distance himself from the symbols of non-Muslims, except for those not intended as a revered cross or a symbol, such as mathematical signs. It is incorrect to link the flowers that Christians believe symbolize the cross with the tree of Bay'at al-Ridwan (Pledge of Allegiance of Ridwan) which 'Umar ordered to be cut, due to the difference in reasons and quantities.