From the perspective of geomantic omen, willow trees on ancestral graves are often considered as a bad phenomenon. Because in Feng Shui, willow represents a place with a heavy sense of suffocation. If there are many willows on the ancestral grave, it means that the gas field around the grave is turbid, which will affect the health and wealth of future generations. Therefore, in geomantic omen, it is suggested to plant flowering plants such as flowers or herbs near ancestral graves to purify the surrounding environment.
Looking at the willow trees on the ancestral graves needs to be analyzed according to the regional cultural background. In some areas, willows are also regarded as auspicious things. For example, in the south, people will regard willow as a kind of "planting trees", which means generations of reproduction, so it is considered a good thing to plant willow in these places. In addition, even the unlucky willow in Feng Shui can't be cut down or uprooted, because it will adversely affect the peace of ancestors.
In a word, willow growing on ancestral graves is just a phenomenon, which cannot be simply attributed to good luck or bad luck. We need to have a deeper understanding of the surrounding environment and cultural background, and make reasonable treatment and response according to the actual situation.
Solemnly declare: the answer is for reference only, please don't be blindly superstitious.