"Senegalia greggii" is most common in arroyos where its roots have access to deep water. Its seeds require physical scarification in order to germinate. This effectively prevents germination unless a flash flood disturbs the area and deposits enough water to increase the likelihood that seedlings will be able to establish deep enough roots to survive the dry season. Catclaw is fully drought deciduous and will usually lack leaves for most of the year. "S. greggii" has extrafloral nectaries, a trait shared with other senegalias. A tentative connection has been made between these glands and insects that would suggest a mutualistic relationship (as found in other "Senegalia" species). Ants are known to use the glands as a source of food and water, and may provide some defense for the plant against herbivorous insects. Like other arroyo trees in family Fabaceae, "S. greggii" is frequently afflicted with Desert Mistletoe, "Phoradendron californicum". Unlike other legumes, "S. greggii" is not known to form root nodule associations with nitrogen-fixing bacteria.