How to Grow Bearded Iris in Australia

What You Need to Know When Growing Bearded Iris

WHEN TO PLANT – the very best time to plant bearded iris is March to mid-April, however other later planting times may result in stunted growth, little or no bloom the first year or can take a long time to get their roots established.

WHERE TO PLANT – For best growth and bloom, iris need at least half to full day sun, 100% sun is best, the more sun and frosts the better the blooms will be IN AUSTRALIA.

SOIL CONDITIONS – BEARDED IRIS need balanced, well-drained soil.  Raised beds will also help with drainage, heavy clay soils need to be amended with gypsum or coarse sand to aid drainage, SOIL should allow a loose root run if other plants grow well in your garden, iris will flourish in it.

HOW TO PLANT – cover rhizomes to about ½ “ (1 – 2cm).  Plant 15 – 20 inches apart (38cm – 45cm) apart, the soil should just cover the rhizomes.  DON’T overfeed and DON’T apply animal manure or excess nitrogen, a general balanced fertiliser is ideal in August and January (e.g) 1 teaspoon of Osmocote per plant or rose food, lightly cultivate in, DON'T cultivate deeply as the feeding roots are near the surface.

WATERING – Iris need a deep watering once a week until they are established clumps, start watering once a week again around bloom time, to get the best blooms.

REPLANTING – In general garden conditions two years on a light soil and three to four years on heavier soil.

DISEASES – Iris are fairly free from problem diseases, the most common is LEAF SPOT.  This is  a fungal disease, it lives in the soil.  When it rains or overhead sprinklers are used, the water hits the ground splashing the spores in the ground up onto the leaves which infects the leaves and causes unsightly spots, just like rose spot, the only prevention is to spray the GROUND around the iris and the iris as well, with a fungal spray, I use Mancozeb Plus, ( there are others on the market as well), when the irises are starting to grow, end of July – September, this gives a coating on the leaves and doesn’t give a chance for the leaf spot to develop, or keep it at bay. Iris love LIME, a sprinkling of lime once a year, l believe this helps with leaf spot too.

RHIZOME ROT – is another disease that can be avoided, it can occur, in the humid and hot weather, due to over watering, or over fertilisation.  A bad practice is mulching with water holding mulch, adding the mulch directly on the top of the rhizomes. The first sign is the leaves go yellow and fall down if this happens check the rhizome, if it is soft, lift the entire clump out of the ground, cut the soft part out (ROT), disinfect the rhizome, with bleach, sulphur or agricultural terramycin, then replant.

GENERAL CARE – Over time iris clumps will become crowded and bloom will suffer.  After flowering simply lift the entire clump with a garden fork.  Cut apart the new, younger “babies” from the older centre rhizome, cutting back foliage like a fan shape and replanting.  Also, the centre rhizome, although it is the largest, will not bloom a second time, so send it to the compost pile. Sometimes you will see new buds coming off the centre rhizome in this case you can replant as before but don’t expect a flower for two years.  Iris don’t like competition from weeds.  Keep your bed neat and clean to allow the sun and air to keep the rhizome dry and happy, REMEMBER – iris are VERY drought tolerant. Water in well on planting then a good deep soak once a week is enough over hot dry periods. Finally, enjoy your iris flowers.  They will produce dramatic, beautiful blooms with minimal care and outstanding blooms with just a little more, happy gardening.

FINALLY – be sure to make good labels.  The labels provided with your plants are not intended for long term garden use.