Doss,
The reason you're finding so much conflicting information on cultural techniques is because there is so much inconsistency in the behavior of irises themselves. Different cultivars within the same iris type may perform better with more or less water, more or less sunlight, or more or less fertilizer. Also, the same cultivar may perform differently using identical cultural techniques in different gardens with different soils and climates. That's why any culture recommendations you read are, at best, general guidelines - a place from which to begin each growing experiment in your own garden.
So, here are my own contributions to the "generalizations" about beardless iris gardening. Most beardless iris types prefer/require acid soil (Spurias being the exception). Most beardless irises prefer a well-drained but moisture-retentive soil high in organic matter that is kept consistently moist, esp. through bloom. Some beardless prefer their soil to dry out between natural rainfalls after bloom. Many beardless may rot if grown in wet soil that never dries out, esp. during high heat (pseudacorus is an exception - it can be grown quite happily with rhizomes submerged in water). They all should be mulched well to keep the soil around their roots and rhizomes cool and moist. In hot summer climates, beardless irises generally need some afternoon shade to protect them from searing sun. In areas with more moderate summer temps, beardless irises will benefit from full sun (foetidissima being the exception - it does best grown in dappled shade).
Hope that helps,
Laurie
