Link to Flora of China description P. elongata has been shown to be related to other species within Section Crystallophlomis based on DNA but morphologically is similar to P. gambeliana and P. rotundifolia. All three may create flowering scapes with double umbels in robust plants. These umbels may not be conspicuous until the plant is in fruit. P. elongata has dimorphic leaves, with bases attenuate in var elongata or with bases cordate in var barnardoana. It may be distinguished from other yellow flowered species in the same range by the presence of farina on the underside of the leaves especially when young and the long capsules.