The Iris genus has a huge range of over 300 species and thousands of cultivars but for the water or bog gardener to make life simpler these can be narrowed down to two broad categories which are appropriate for our needs. It is important to differentiate these as bog irises will not survive in the pond whereas water irises are best in the pond but will also grow in a bog garden that is reliably moist throughout the year.
The first group comprises the true water irises. These grow best with water over their crown all year around and include Iris pseudacorus (yellow flag), Iris versicolor (blue flag), Iris laevigata (rabbit ear iris), Iris viginica (southern blue flag), Iris fulva (red flag or copper iris) and Iris prismatica (cube-seed iris). Some of these are referred to as a type of “flag” as they marked the shallow area in a stream where travellers could safely cross.
The second group are the bog irises, which grow best in wet or damp soils and will tolerate drier conditions for part of the year. They can also grow in shallow water but will not survive in the pond all year round so would have to be moved out of the pond to a drier spot in the winter months -not very practical! Amongst others, these include Iris ensata (Japanese iris) and Iris sibirica (the Siberian irises).
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