Final answer:
Undesirable characteristics of hay can include the infusion of harmful plants like sandbur, the presence of weeds such as dyer's woad disrupting intended land use, and hay-storage problems akin to those caused by weeping willow roots in drainage systems. Additionally, microorganisms like Rhizobium might be negative in nitrogen-rich environments.
Step-by-step explanation:
Some undesirable characteristics of hay may mirror issues similar to those presented by various plants and organisms in agriculture and ecology. For instance, hay that is infested with sandbur could pose a threat to animals due to its sharp fruits, which are not only painful to step on but may also stick to fur and clothing, much like how sandbur is a nuisance on beaches.
Another issue is the presence of weeds like dyer's woad, which, despite its historical use as a dye, is classified as an agricultural weed when it disrupts the management of land for other purposes. In addition, plants like weeping willow trees, although ornamental, have root systems that can potentially clog drainage systems, which could be analogous to problems in stored hay that may harbor plants whose roots cause similar issues. Lastly, microorganisms such as the nitrogen-fixing bacterium Rhizobium might be undesirable in hay if they lead to decreased plant growth in environments where nitrogen is already plentiful. This reflects the complexity of agricultural ecosystems where organisms can have both positive and negative impacts.