Harveya

Harveya is a genus of fleshy, holoparasitic herbs, commonly known as inkflowers, forming part of the Orobanchaceae or broomrape family, previously Scrophulariaceae. The annual and perennial plants attach underground to the roots of host plants, fully dependent on their hosts for survival.

The leaves are usually only scales, especially the lower ones. The leaves are usually opposite, the upper ones sometimes alternate and more spaced or fewer. The blades are often yellow, lacking chlorophyll and turning black when dry. The host is compelled to share its nutrients, not bear the flowering parasites offspring.

The usually large, sometimes stalked flowers grow in spikes or racemes from leaf axils with bracts and bracteoles present. The flower stems may lengthen during fruiting. The tubular, five-lobed calyx is sometimes two-lipped and glandular-hairy. The tubular corolla is slightly curved and two-lipped, also five-lobed and coloured yellow, red, pink or white.

The four stamens usually have one anther lobe sterile, the other hooked. The stamens are included or slightly exserted, the linear filaments arising from or just below the middle of the corolla tube. The ovoid, ellipsoid or obovoid ovary has two locules containing many ovules. The thread-like style is curved, as long as the corolla tube.

The fruit is a variably shaped capsule. The numerous seeds are small, and variably shaped. The inkflower seeds germinate underground, having been washed there by rainwater through the loose sandy soil of the plants habitat. Harveya plants produce huge amounts of seeds for reaching a statistical survival chance in this unlikely propagation system. 

For the new life to continue, the germination has to occur near a living root of almost any shrubby species, promptly imposed upon through a durable attachment for appropriating some of the host plant’s life-giving resources. A little like siphoning fuel from a parked car, but the link becomes durable, lifelong, being underground. 

There are about 40 Harveya species in Africa and the Mascarene Islands. About 25 are found in southern Africa, 9 in the fynbos and 7 in the Little Karoo.

The plant in picture is Harveya capensis (Leistner, (Ed.), 2000; Vlok and Schutte-Vlok, 2015; Manning, 2009).