Iris sibirica

Tall, deciduous iris that forms large clumps up to 0.6m tall and 0.5m wide.

Through early summer Iris sibirica produce flowering stems to around 70cm tall bearing 2 to 4 flowers per stem. Flower colours range from white and cream through hues of blue to dark purple. Foliage is erect and grass-like and is usually shorter than the flowering stems at around 50cm tall.

This iris prefers acidic soil free of lime and rich in organic matter. It can grow in heavy clay soils and loves wet feet. Best planted in full sun to part shade.

During the growing season, it thrives in standing water (up to 15cm deep). However, in winter, it is intolerant of both standing water and boggy soils where it may rot. Siberian iris grows surprisingly well in garden soils as long they receive consistent moisture.

Plant when the soil is moist and warm in autumn or early spring so that a good root system develops to support vigorous new growth. Remove all perennial weeds. Incorporate bark compost or other organic material. Before planting, ensure the root ball is saturated and remove the planter pot with minimal root disturbance. Trim any broken roots and plant at the same level as in the container. Dig a hole twice the diameter of the root ball, press in and water once planted. Make sure plants are watered well until established if planting in a drier period. Plant with some general slow release fertiliser and then every spring apply an organic fertiliser (such as blood and bone) at a handful per square metre as new growth appears. Do not apply lime, as Iris sibirica prefer the soil to be more acidic.

Planting too closely leads to spindly growth, poor flowering and eventual decline. In a well-planned border, flowering plants should just touch each other to create a full effect without overcrowding. Plant approximately 60cm apart.

When planting a pond, make sure the crown is planted above water level to help prevent damage from ducks and pukeko. Cover area with wide-meshed wire netting to discourage birds. To suppress weeds and stabilise the ground, periodically apply a thick mulch of gravel.

Apply mulch annually to suppress weeds and conserve moisture. Groom plants occasionally during the summer by removing spent flower stalks and dead leaves. Apply organic fertiliser in spring at a handful per square metre or less. Too much fertiliser may result in leafy growth at the expense of flowers.

Plants may be left undisturbed for four to five years before lifting, dividing and replanting. This can be achieved by lifting the plants, putting two garden forks back-to-back through the clump and pushing apart. The resulting clumps should be immediately replanted where they are to flower. If they are left for several years without being divided, they do not perform as well. Dividing not only gives you more plants, it also rejuvenates them. Do not disturb plants if they are healthy and flowering well. Division is best done in autumn.

Birds eat the seeds.

TBC

Seed heads can be left on over winter as food for birds.