Well-suited to Houston’s climate and usually disease-free, Louisiana Iris bloom during March and April. Irises need a half-day of sun. Plant rhizomes immediately, placing them just below surface in a bed level with a lawn, or in a low spot. Fertilize one or twice a year, flooding the bed in January before blooming. Water sufficiently in summer to maintain active growth. Mulch in summer to prevent sunburn. If properly watered and fed, they may be left alone for years.