Lack of bloom can be caused by a number of factors and usually a combination of more than one. They are a bit like people -- give them a bit of room and satisfactory conditions and they will perform well. Here is a list of some of the more common culprits:
- Planting in too much shade. They need at least 6 hours of full sun per day.
- Over feeding with animal manure or fertilizer high in Nitrogen. (We recommend a low-Nitrogen fertilizer, such as a 6-10-10 mix).
- No feeding at all. Starved Iris will not flower.
- Planting too deeply. Tops of rhizomes should be visible above the soil level. (In extremely hot areas of the country, cover tops of rhizomes with only about 1 inch of loose soil or sand to prevent sun scorching.)
- Mulching with lawn clippings or other organic matter. Don't mulch, as it acts as shade and can cause rhizomes to rot.
- Over or under watering can also cause problems. Plant Iris is well-drained soil. Water deeply once every week or two during the dry spring and summer months.
- Overcrowding: they need dividing every 3 to 5 years.