When fertilizing around a tree, the guidelines suggest not to exceed what multiple of the canopy diameter?

The correct choice reflects the established guidelines for fertilizing around trees, which suggest that the application area of fertilizer should not exceed one and a half to two times the diameter of the tree's canopy. This is important for several reasons.

First, applying fertilizer beyond this range can lead to wasted resources as the nutrients may not reach the root zone effectively. Tree roots generally extend outwards to about the same width as the canopy, and excess application can also contribute to potential nutrient runoff or leaching, which may harm the surrounding environment and lead to pollution.

Additionally, proper fertilization practices help ensure that the tree receives sufficient nutrients without the risk of over-fertilization, which could damage the tree and the surrounding soil. By following this guideline, growers and landscapers can promote healthy tree growth while minimizing negative environmental impacts.