Ceanothus greggii looks similar to Ceanothus fendleri in that it is a shrub with small leaves. The branches on Ceanothus greggii are opposite, while those on Ceanothus fendleri are mostly alternate. The leaves of Ceanothus fendleri are conspicuously three veined from the base, while those of Ceanothus greggi are reticulately veined. The leaves of Ceanothus greggii are pubescent below along the midvein and in tufts. Also, the branches of Ceanothus greggii are not armed like those on Ceanothus fendleri. Ceanothus greggii prefers dry slopes in lower to middle elevations, while Ceanothus fendleri is found higher at middle elevations. Finally, Ceanothus greggii blooms in the early spring, while Ceanothus fendleri blooms in mid-summer.