How to grow irises for wet or moist soil

Choosing an iris for wet or moist soil

The main species of iris that like moist soil are Iris laevigata, Iris ensata and Iris pseudacorus. They are all sold either as bare-rooted plants or potted in compost

Can refer to either home-made garden compost or seed/potting compost: • Garden compost is a soil improver made from decomposed plant waste, usually in a compost bin or heap. It is added to soil to improve its fertility, structure and water-holding capacity. Seed or potting composts are used for growing seedlings or plants in containers - a wide range of commercially produced peat-free composts are available, made from a mix of various ingredients, such as loam, composted bark, coir and sand, although you can mix your own. .

• Iris ensata needs rich, acid soil, but does not grow in standing water
• Iris laevigata prefers an acid to neutral soil
  The acidity/alkalinity of soil is measured on a pH scale, which runs from 0 to 14. Soil classed as neutral has a pH between 6.5-7.0, even though a pH below 7 is still technically acid, because the widest choice of plants grow in this range. You can easily check your soil pH with a simple testing kit, widely available in garden centres or online. Many plants thrive in neutral soil, except those than need notably acid or alkaline conditions. and can grow in pond margins
• Iris pseudacorus grows best in acid soil, but will tolerate a neutral pH
  This describes how acid or alkaline soil is, and is expressed as a number between 0 and 14. Soil with a pH of 7 is neutral, an acid soil has a lower value, and an alkaline soil has a higher one. Most plants grow best in soil that’s within a specific pH range, so it’s useful to know your soil’s pH. Testing kits are easy to use and widely available in garden centres and online. and can grow in pond margins. It is very vigorous

There are variegated

Variegated means having leaves or other plant parts with streaks, blotches or patches of different colours. Typically, these would be a combination of two colours, such as green and gold or green and white. versions of these irises, which may add an extra colour dimension and extend the interest in your garden.

It isn’t always easy to find a good selection in garden centres, so consider visiting a specialist aquatic nursery or buy online using our Find a Plant.

When to plant irises for wet or moist soil

April is the best time to plant, as their roots will have a full growing season

The period of time when an individual plant is in active growth. This will depend on the local climate and light levels, and can vary between different plants, although it is broadly from spring to autumn. to get established. However, you can plant from March to mid-November as long as you water to keep their roots moist while they establish – thankfully, if planted on the margins of a pond, this won't be needed anyway.

Where to plant

Bog gardens, the edge of a pond or a damp border, are good places to plant water irises. They all need a sunny spot and planting 50cm (20in) apart. They are hardy and will be happy in all UK climates.

How to plant

If you’re planting Iris laevigata or Iris pseudacorus into shallow water, use peat-free aquatic soil and baskets. This can help prevent the irises from becoming too invasive

Invasive plants are those that grow vigorously, spread rapidly and can out-compete other plants. Native, non-native and cultivated plants can all be invasive. , and the baskets certainly make it easier to lift and divide clumps compared to those planted in the mud at the base of a pond near the water's edge.

If you’re planting into moist borders, plant as you would any other herbaceous perennial.

• Plant Iris laevigata and Iris pseudacorus rhizomes
  Rhizomes are creeping swollen root-like structures that are actually adapted stems. Roots, stems with leaves and flowers are produced along its length. See plants such as Anemone nemorosa, bamboo, canna, border iris. level with the water surface
• Make sure that Iris ensata crowns are not submerged in water

Caring for older plants

The main job will be dividing congested clumps of irises. You can do this summer if they are taking up to much space or when flowering declines. Usually, this is done every three years or four years.

Pruning for wet or moist soil

You can cut away the spent flower stems once the flowers have faded. Remove the stem down to where it meets the foliage.

By November all the foliage and old flower stalks will die off, so all you need do is cut them off at ground level (or just above the new shoots if this task gets left to late winter).

Propagating

The easiest way to share irises with your friends is by division in summer after flowering.

• Lift the rhizomes
  Rhizomes are creeping swollen root-like structures that are actually adapted stems. Roots, stems with leaves and flowers are produced along its length. See plants such as Anemone nemorosa, bamboo, canna, border iris. (swollen root-like structures that are actually adapted stems) and shake off the soil
• Use a clean knife to cut healthy young rhizomes into short sections of about 10-15cm (4-6in)
• Try to make sure that each section has roots attached and one ‘fan’ of leaves
• Throw away any rooting pieces with holes in them, or no roots or foliage
• Trim the roots by up to one third and trim the leaves down to 15cm (6in) (naturally giving you a fan shape)
• Plant the rhizomes 3-5cm (1¼-2in) deep, in the bog garden, moist border or basket if you are planting into a pond
• Be sure the new divisions don’t dry out

You should have some flower the following year, but the performance will be even better in the second year after division.

For a more challenging project, you could try growing irises for wet or moist soil, from seed.

• Collect the seed pods when they are ripe in autumn
• When ripe, the pods will change colour to brown and start to split open. Shake the seed into a paper bag
• Soak the seed for 48 hours and sow on the surface of peat-free John Innes Seed Compost
  Seed compost is a free-draining compost formulated for germinating seed. It often contains a mix of fine materials including sterilised loam, coir, coarse sand or grit. It contains low levels of nutrients, as high levels could damage seedlings. mixed with 25% extra grit by volume. Cover the seed with a thin layer of grit
• Place the seed tray
  A seed tray is a shallow, vertical-sided, rigid plastic or wooden tray with drainage holes in the base. It contains enough compost for seeds to germinate and grow into seedings, but then they'll need transfering into pots. /pot in a cold frame
  Cold frames are glaze box-like structures made from brick or wood with a  hinged or removable, glazed, sloping lid. Useful to protect plants from cold weather over winter or acclimatise (harden off) young plants in spring and provide extra warmth for tender crops in summer. or at the base of a wall for shelter
• The seed should germinate in spring, but the seeds may not come up all at once. Don’t give up –more seed may germinate in the second year
• Seedlings
  A seedling is a young plant grown from seed. from named cultivars do not ‘come true’ and will produce a range of flower colours
• They take two years to reach flowering size

Irises for wet or moist soil don’t generally suffer from pests and diseases.