Tilburg stands on sand, and the trees show it. The city is ringed by pine plantations laid down to fix drifting sand — De Kaaistoep, the Oude Warande, the woods towards Goirle and Loon op Zand. Pine produces enormous quantities of pollen in spring, visible as yellow dust on cars and puddles, but it is a weak allergen: many people blame the pines while the birches standing among them are the real cause.
Those birches are certainly there, because on poor sandy ground birch is the first tree to come up. The Oude Warande and the Leijpark add old beech and oak, and along the Leij there is alder and willow in the wetter stretches. The second season is agricultural: the Kempen around Tilburg is farmland, grass and cereals, which makes late May to mid-July the heaviest period of the year. Tilburg lies far enough from the coast to gain little from the maritime dilution that the Randstad regularly receives.