This is the very best time of year for studying the "bottom of the wall" plant community. It occupies 5-20 cm of pavement or tarmac at the bottom of the wall and hasn't yet had a chance to be weeded or herbicided. I'll go through the species in pairs in the following tweets.

Erophila verna (Brassicaceae, left). Arabidopsis thaliana (Brassicaceae, right).

Poa annua (Poaceae, left). Sagina procumbens (Caryophyllaceae, right)

Capsella bursa-pastoris (Brassicaceae, left). Senecio vulgaris (Asteraceae, right)

Geranium robertianum (Geraniaceae, left). Soleirolia soleirolii (Urticaceae, right)

Lamium purpureum (Lamiaceae, left). Cerastium glomeratum (Caryophyllaceae, right)

Veronica arvensis (Veronicaceae, left). Epilobium ciliatum (Onagraceae, right)