The BC2S1 and BC2S2 generations were grown in the field at Lawes, Queensland, and selected for both disease resistance and agronomic characters, while the BC2S3 and BC2S4 were glasshouse-grown and selected for stem rot resistance. The BC2S5 generation was grown in the field and selected for uniformity of plant and seed type. Holstein is an erect annual cowpea with a moderate vining tendency when grown in decreasing daylengths in south-eastern Queensland. Sowings before the summer solstice or under high rainfall and high temperature conditions can have excessive vegetative growth, prolonged flowering, and increased vining with a consequent loss of the erect habit. At crop density, plants may have up to 9 branches bearing dark green trifoliolate leaves on petioles of 120 mm average length.
Leaflets are deltoid-shaped.
When freshly opened, flowers have a yellow standard petal. Pods are borne on peduncles up to 600 mm long and are mostly in the upper canopy layer. Pods are dark green with a red upper suture when immature and a straw colour when dry. Pods range from about 120 to 200 mm long and contain 5-16 rhomboid seeds, black and white coloured, in a holstein pattern. In plant morphology and phenology it is similar to Banjo, but its resistance to stem rot disease extends its range of adaptation to soils where that disease is likely to infect crops.