The lower leaf surface of Senecio maritimus is finely hairy, causing it to be paler than the upper one. The midrib is dark here, the lateral veins pale and clearer to see than on the upper surface.

The more numerous, smaller leaves display the conventional toothing pattern of the species (Manning, 2007; Manning and Goldblatt, 1996; Bond and Goldblatt, 1984; iNaturalist).