Soil pH for Lily bulbs
Sandy loam soil, rich in humus, with a pH of about 5.5 to 6.5 is the textbook ideal. However, most varieties can tolerate more acidity or even slightly alkaline soil and still produce good results. In general, Orientals do best if soil is amended with peat moss or other components to achieve at least slight acidity. Asiatics, Lilium martagon, L. henryi, L. regale, L. pumilum (and their hybrids) perform wonderfully in neutral to slightly alkaline soils in all climate zones. Trumpets will grow happily with slightly alkaline conditions, but need protection from severe late spring frosts if sprouts have emerged.