It's largely a waste of water. The purpose of the yellowing foliage is to feed the bulb for next season; I don't recommend trying to delay that natural process. And lilies don't like overwatering - the bulbs could rot.

Thanks so much! I never knew you could just let them go. so should I water them at all during the summer?

Jen

The lily bulbs themselves pretty much contain what they need to put up stalks and blooms without a lot of fussing and human intervention. If your soil drains and nothing is sitting in water, natural rainfall or periodic supplemental watering is fine. Lily bulbs just don't like "wet feet".

I know your question was about lilies, but you can hide the yellowing foliage behind other plants which stay quite clean looking late into the season. What I do is try to keep plants/perennials with the same water requirements in the same area (called hydro-zoning) - several varieties of Oriental and Asiatic lilies, true tiger lilies, balloon flowers (platycodon), sedums of all types, daylilies, tall bearded iris, Siberian iris, and nepeta all do well in drier conditions. Some other low water perennials are purple coneflowers, baby's breath, delphiniums, poppies, salvia, coral bells (heuchera), liatris, dianthus, and peonies.

Low water annuals for borders or fill-ins would be petunias, forget-me-nots, ageratum, alyssum, lisianthus, hybrid verbena, cleome. There really are so many more perennials and annuals that will do well when left on the dry side.

I have everything mentioned above except delphiniums and cleome - we had very little consistent, meaningful rain this summer and I don't do a lot of supplemental watering. Despite it all, my gardens did quite well.

I'm sure others may have different opinions on different plants and their particular requirements - as we all have different soils, micro-climates, sun exposures, etc. , but we'd all pretty much agree that lilies will be fine without a lot of extra watering.