Daylilies (Hemerocallis spp.) are hardy garden perennials with flowers that open for a single day. They tolerate a wide range of soils, according to the American Hemerocallis Society.
In gardening, alkalinity refers to a pH of above 7 in garden soils, indicating basic rather than acidic conditions. Daylilies prefer slightly acidic soils with a pH of 6 to 6.5, advises the Clemson University Extension.
Although daylilies can adapt to most soils, the All-American Daylily
Selection Council gives the example from their research of the cultivar, Ming Toy, which rots in alkaline soils when temperatures are warm.
Worry about soil pH only if your daylilies aren’t doing well, recommends the American Hemerocallis Society. Test your soil before adding sulfur to reduce alkalinity. Another way to decrease soil pH for daylilies is to till in compost or other organic matter, according to the Colorado State University Extension.
The color intensity of some daylily varieties changes with soil alkalinity and acidity, according to Washington State University Kitsap County Extension’s Peg Tillery.