At this time of year you may observe two interesting fungal colonisers through lawns. These gain a foothold during dank and humid conditions where they often colonise poorly drained lawns with a sward of disputable quality. More frequently occurring where tree cover is also reducing light to the area.
Yellow Club Fungi, Clavulinopsis helvola: mini pillars of fungi sprouting above closely mown turf. These are an attractive yellow colour making it easily recognisable.
Dog Lichen, Peltigera canina; a fast colonising, grey, ear shaped lichen that responds to cultural control.
When dry it will shrivel to a crisp yet absorbing water as the weather changes.
Neither the fungi or the lichen are a problem in a poor quality lawn and by definition to improve the quality of the turf good drainage and light quality are essential. Doing this will then reduce the diversity of fungi and lichen found through lawns.