The most important special cultivation in Hertfordshire is undoubtedly watercress, which is very extensively grown in the river-valleys over a broad belt of country extending from the Welwyn district, through the parishes of Harpenden, Wheathampstead and Redbourn, and thence to Amersham and Rickmansworth, as well as to the Vale of Aylesbury in Buckinghamshire; this district being reported to be the best in England for this particular crop. The cress is grown in beds cut through the low-ground from one bend of the river to another, so that a constant, but regulated stream of water is continually flowing through. The seed is sown in special beds, and the young cress carefully planted out in regular rows in the mud of the permanent beds during the autumn. Much care has to be exercised in tending and weeding the crop, from which two prolonged cuttings are obtained annually; the spring cutting being, however, much larger and better than the autumn one.

After cutting, the watercress is tied up in bundles and packed in flat, oblong, osier hampers, or baskets; of which, during the spring season, huge stacks may be seen at the local railway stations awaiting despatch, either to the metropolis, or to the great manufacturing towns of the Midlands. For ordinary purposes the land on which watercress is grown is almost valueless; but the watercress beds yield a big rental. To furnish material for the aforesaid watercress hampers, as well as for basket-work generally, osiers are cultivated in some of the river-valleys, as in the Lea a mile or so above Wheathampstead, where there are extensive beds.

Next in importance to the cultivation of watercress in the Harpenden-Redbourn district is that of lavender at Hitchin, where numerous fields on a spur of the chalk range near Windmill Hill are devoted to the growth of this fragrant plant. In late summer or early autumn the terminal spikes of blossom are nipped from their long stems, and garnered for the sake of their contained oil, which is distilled into lavender-water in Hitchin itself. Lavender-water has been produced at Hitchin for a period of fully eighty years. The growing of lavender as an industry is extremely restricted in England.