My half-acre garden has become increasingly shady over the last 35 years, and some irises have ceased flowering as a result. 35 year old bearded of all different sizes still thrive as foliage plants, and will flower the year after I do major tree pruning in their area. Siberians also require sun, but not just for the flowers. Eventually the leaves start to grow weakly. Louisianas have never flowered - too cool in summer, probably, though I have them in a sunny spot. We're zone 8 for winter, but most summers have 0 "degree days" which I think is days above 30C (?), and in the rare years that we do get such a torrid day or two, the nights will be much cooler. I. cristata and unguicularis do OK in shade from deciduous trees, as does japonica. Pacific Coast hybrids and Oregon species thrive and flower in any conditions. I am developing ones with up to nine flowers per stem, some that bloom in April and again in midsummer, and some that are small enough for a rock garden trough. It is exciting every spring to see what the new seedlings will be like. Reticulatas have to be watched assiduously or the slugs will have them disappear as soon as the buds emerge. -- Diane Whitehead Victoria, British Columbia, Canada maritime zone 8 cool mediterranean climate (dry summer, rainy winter - 68 cm annually) sandy soil