Excavator: ground. Females excavate their nesting burrows in sandy soil. In Devon, G.M. Spooner (pers. comm.) and Hertfordshire, R. Uffen (pers. comm.) observed specimens in holes in wood, but these were probably sheltering rather than nesting, although, in mainland Europe the species is reported to nest in such locations (Banaszak & Romasenko [as M. argentata], 1998; Peeters, Raemakers & Smit, 1999). In Denmark and the Netherlands, the species may nest in very concentrated aggregations (Holm & Skou, 1972; Lefeber, 1983), but this behaviour is not commonly noted in Britain. On Hayling Island, Hampshire, for example, the species is usually extremely plentiful and may be the dominant bee there in late June and July, but its nest entrances seem to occur in loose aggregations.Two nests were also located there which were excavated in sand which had accumulated as low mounds at the base of grass tussocks.
Praz (2017) reports that generally, Megachile leachella nests primarily in burrows dug by the bee in sandy soil and uses leaf discs to build its brood cells
Generally cells are constructed from leaf sections cut from various plants, including Clematis vitalba, Parthenocissus, Laburnum, Robinia, Rosa canina, Hippophae rhamnoides, Ulmus, Alnus, Salix, Syringa, Oenothera and Solanum dulcamara (Smith, 1876; Nielsen, 1902; Crèvecoeur, 1952; Grandi, 1961; plus records supplied by G.M. Spooner, and pers. obs.). F. Smith (1876) frequently found cells built from the yellow petals of Lotus corniculatus. The nest architecture has been described by Grandi (1961), who also describes and figures the mature larva. Holm & Skou (1972) also figure the cocoon; they discovered that the innermost cells of a nest invariably produce females, whereas males emerge from those nearest to the nest entrance.