Fields and livestock
In 1686 Diegem consisted almost entirely of fields: 354 of its 395 bunders were grain land, plus some meadow, woodland and 16 bunders of ponds. By 1846 the grain land had halved and there were many more fodder crops, a sign of larger herds. A livestock count of 14 April 1809 recorded among others 32 horses and 105 cows, but no sheep. In 1845 the potato blight struck; the municipality then had 80 hectares of potatoes.
Chicory
Chicory roots were already grown in the area for cheap ‘chicory coffee’, and Diegem had several chicory manufacturers. Around 1850 a head gardener at the Brussels Botanical Garden discovered that the roots, covered with a layer of soil, produced a white, tightly closed head: witloof, Belgian endive. In 1867 the farmer Lekeu brought the first field-grown witloof to the Brussels market. In Diegem cultivation grew especially between 1907 and 1910, and Diegem-Lo became known for it. For three quarters of a century witloof brought prosperity, until the airport, the interchanges and the motorways took the land. By 1977 there were only ten farms left, with 6.5 hectares of witloof and not a single horse, cow or pig.
Industry
Besides the mills and stone pits, Diegem had two mustard mills in 1671, unique around Brussels. Around 1900 there was a margarine factory, the cardboard works and an ironworks; later came the Ermens brewery, Marga's munitions factory, fur works, the Hendrix wallpaper factory (1920), a metal foundry (1925) and the Reno stove factory (1936-1937). After 1945 the airport at Melsbroek and new firms such as the Biscuiterie Royale and the Sabena car depot attracted workers. In 1961-1962 an industrial zone was marked out between the Brussels-Leuven railway, the Pachthofstraat, the Bosstraat and the Lambroekstraat; in 1970 it was extended to about 100 hectares.
In 1976, 2,616 people from 387 municipalities worked in Diegem every day; 92 per cent of those employed there came from outside. Conversely, most people from Diegem worked in Brussels or in Halle-Vilvoorde. In 1957 the village still had 35 pubs; twenty years later about ten remained.