Most early references to prickly pear are neutral in their tone, or like Mary Barber's, rejoiced in its familiarity and utility. Yet as early as the 1860s, when much of the rural Cape was being transformed into sheep territory, a few white farmers claimed that they were driven from their land by prickly pear. Soon afterwards key officials and experts became increasingly concerned about opuntia. One of these was Henry Bolus, a committed amateur botanist after whom the Bolus herbarium at the University of Cape Town is named. He lived for some years in Graaff-Reinet where he studied Karoo plants and landscape. In 1874 he wrote:

Bolus was struck by the ‘sociable’ nature of prickly pear which was rare amongst indigenous Cape plants. By sociable, he meant that large numbers of the plant grew together in dense thickets, whereas many indigenous Cape plants tended to be more solitary. This intensified its impact on indigenous vegetation. Peter MacOwan, who botanised with Bolus in the eastern Cape, and later became long-serving Government Botanist in Cape Town, kept a worried eye, during the 1870s and 1880s, on major thickets near the Bruintjieshoogte pass, and also at Cookhouse.