Jacob van Reenen, son of Jacob van Reenen and his wife Maria C. Persoon, was the fourth in a succession of men with that name, the first being his great-grandfather, who arrived at the Cape from the Netherlands in 1722. The younger Jacob became a prominent farmer on Ganzekraal, a farm on the west coast some 50 km north of Cape Town, where his father had settled in 1798. On 16 October 1808 he Married Sophia M.J. van Schoor, with whom he had one son and one daughter. He has been credited with founding the Dutch Reformed Church at Darling (Heese, 1986-2005).
In November 1831 Van Reenen became a foundation member of the Cape of Good Hope Agricultural Society and was elected a member of its first committee. He was not re-elected in January 1833, because he lived too far from town to regularly attend meetings; however, he served on the committee again from about 1837 to about 1855. In March 1837 he was one of the wool judges for the society and at its show in September 1850 won the largest prize (£10) for entering the best thoroughbred colt. However, his most significant contribution to agriculture was probably his invention of a machine for cutting grain on the land, which was to be submitted for inspection at the society's show on 23 September 1847 in Cape Town. Unfortunately no further mention is made of this machine in the South African Commercial Advertiser's report on the show. During the previous month he had acted as a judge in a ploughing contest arranged by the Caledon Agricultural Society.
Jacob van Reenen, presumably him, wrote a paper on "Early discoveries of gold", dated February 1854. The paper does not appear to have been published, but was included in the T.R. Jones* collection of papers and manuscripts on the geology of South Africa.