's-Hertogenbosch stands on the river clay where the Dommel and the Aa meet, and it is one of the wettest urban settings in the country. The Bossche Broek, De Moerputten and the Vughtse Gement press right up against the city: low-lying, boggy meadows and marshland. That is grassland, and it makes the grass season from May to mid-July the heaviest part of the year for anyone living here.
The same wet ground carries the woodland that belongs to it: alder carr and willow beds along the stream valleys of the Dommel and the Aa. Alder is the earliest flowering tree in the Netherlands and starts in January in mild weather, so the season opens here sooner than the average national report suggests. South of the city, towards Vught and the Loonse en Drunense Duinen, the soil turns to sand and the birches appear, peaking from late March to early May. Early alder, birch on the sand and a great deal of grass on the clay together give 's-Hertogenbosch a season that begins early and does not really ease until mid-July.