This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Known only from its distribution to-day in the North Temperate Zone, Pennywort is found in Europe from France southwards, W. Asia, the mountains of N. and Tropical Africa. It is found in Great Britain throughout the Peninsula province, and in the Channel province except in N. Hants, in Kent; in S. Wales except Radnor; N. Wales; in the Trent province only in Leicester and Derby; in S. Lancs, S.W. and N.W. Yorks, the whole of the Lakes; in Scotland in Kirkcudbright, Ayr, Renfrew, Argyle, Clyde Islands, Cantire, Mid Ebudes, especially on the west coast. It ascends to 1000 ft. in Wales. It is native in Ireland.
Moist, dripping, flat-surfaced, perpendicular walls, intersected by numerous crannies and fissures, are the special habitat of Navelwort, which is a shade-loving rock plant, found wherever Orpine, Stone Crops, Goldenrod, Wall Lettuce, and many ferns, such as Wall Spleen-wort and others, grow.
Pennywort has much the same habit as Grass of Parnassus, but the stems are more numerous and prostrate at the base, while the flowers, too, are in a raceme. The stems are succulent, stout, rounded. The leaves are thick, shield-like, the leaf-stalk being central below the leaf, which is hollow (hence the first Greek name and the second Latin name), scalloped at the margin, smooth, fleshy, and shiny. All the leaves are stalked, and chiefly radical. From the round, flat nature of the leaves they are known as pennies, hence the English name.
The bracts are simple, towering gracefully above the characteristic leaves. The greenish-yellow drooping flowers are arranged in a simple raceme, alternate. The flower-stalks are very short. The corolla is cylindrical. The seeds are contained in follicles.
Pennywort reaches a height of 6 in. to 1 ft. or more. The flowers are in bloom in June and July. The plant is a perennial plant, which may be propagated by cuttings.
The green flowers are not attractive to beetles, and though large and bell-shaped they grow in situations where insects are not likely to reach them readily, and from the adnate stamens, which are included in the corolla, and the many short ovules, the plant is more liable to be self- than cross-pollinated. Thrips visits but does not pollinate the flowers. The anthers ripen first.