Multiple possible sources of difficulty mentioned: root competition from grass, root competition, blocking of rainfall and sunlight by taller trees, possible inadequate watering, and browsing by deer, which are quite apt to clip willows to the quick.

Full sun and abundant soil moisture for willows generally. However, dappled willow has some very pale portions of foliage that will burn in full sun, so you have to split the difference and give it light shade.

Thank you, bboy. All of the factors most likely had some part in this saga, but the deer might be the main culprits. As the saying goes, "they were here first", and there are no indications that they plan to leave any time soon, at least not where we live. So, no more willows out there, but we still like them. Would you recommend them as container plants for our patio, or are they really best in the ground?

They are frequently available as "patio trees" or grafted on standards to resemble small, variegated pom-poms. These are quite easily grown as container specimens, but will require the same light and water conditions as bboy outlined above. They can be pruned/shaped at will to keep tidy and each pruning will result in a new flush of pink new growth.