It has long been suggested that phylogenetic divergence between parental species determines the likelihood of their producing a successful polyploid, with closely related parents less likely to form a successful polyploid than more divergent parents. This suggestion has been based partly on observation of patterns of polyploid ancestry and partly by extrapolation from analyses of the processes that give rise to polyploids. Here we present a new survey of the patterns of the divergence between the parents of polyploids, based on node-based and clade-based analyses of phylogenetic trees. We also use the topology of the phylogenetic trees to inform a null expectation of the distance between parental species, assuming random crossing between all species pairs in a genus. We used molecular phylogenies now available for eight plant genera containing multiple polyploids whose parentage has been investigated: Tragopogon, Persicaria, Brassica, Leucaena, Spartina, Spiranthes, Nicotiana, and Glycine. We found that the phylogenetic distance between progenitors of polyploids did not differ significantly from the null expectation. In contrast, the distance between parents of diploid hybrids (both stable and unstable) in these genera were lower than would be expected with random crossing. We discuss how these findings may fit with recent progress, through genetic and genomic studies, in understanding the processes involved in polyploidization.