How to Grow: Tall Bearded Iris

Discover everything you need to know about Tall Bearded iris from Sandra Ross in conversation with expert iris growers, John Taylor, Graeme Grosvenor, Lyz Taylor (Kinspirit Iris), and David Kennedy (Highfield Garden, Little Hartley).

The Irisgenus is a complex one. It comprises approximately 270 species – all of which have six petal-like structures, called ‘tepals’. The three upper tepals are known as ‘standards’ and the three lower as ‘falls’. Bearded iris have decorative ‘beards’ at the base of each ‘fall’.

Flowering season

Tall Bearded irises flower in October and November. Repeat flowering cultivars flower again in late summer.

When to plant

Tall Bearded irises grow from a fleshy rhizome. They should be planted in autumn, as all their new root development is done in late autumn and early winter. Never transplant bearded irises in spring.

Where to plant

Bearded irises need an open position where they can feel the breeze. To flower well, bearded irises need full sun, at least six hours a day. They make great companion plants for roses as they like the same conditions.

The best soil forbearded irises

Bearded irises grow best in well-drained soil. They dislike sticky, heavy-clay soils. A good friable loam that receives moisture but is well drained is best. If the soil is heavy and needs breaking up, dig in quantities of spent mushroom compost or home-made compost. Be wary of animal manure as iris don’t like too much nitrogen. They also prefer soil to be slightly alkaline. Acid soil should be limed with dolomite.



If you are preparing a new garden bed, wait one full month after preparing the soil to allow it to properly settle. 

How to plant

Tall Bearded irises grow from a fleshy tuber-like rhizome which should be planted at ground level, not beneath the soil surface, ensuring maximum heat retention, not moisture retention. Secure each piece of rhizome in place with a bent section of wire to stabilise in the soil so roots will grow.

Feeding and watering

April and August are the optimum months to feed iris. Apply well-rotted compost and a handful of lime. Include powdered potash with the August feed to promote bigger and better blooms (a general rose fertiliser will suffice). Water regularly but not too much. Give them a good soaking then allow them to dry.

When to lift and divide

Flowering reduces when plants require division to removes pent rhizomes, which could otherwise retain moisture. Mid-to-late summer is the best time to lift and divide iris clumps, after flowering has finished, and new roots are forming. Any later and you will damage those new roots. Discard spent rhizomes, trim foliage back by one-third to reduce transpiration and trim the roots before replanting. This will mean your new divisions are settled and will get growing in time to produce flowers next spring. This process should be repeated every three years.

 

Which iris?

Iris catalogues give little information on performance or awards that an iris might have earned. The Iris Society of Australia runs trial gardens to evaluate the worth of new cultivars. The best performers in regional trial gardens are then eligible for evaluation nationally. The national program involves growing the eligible iris in a number of trial gardens around the country for three years to enable the performance of an iris to be evaluated in a range of conditions. Each year the cultivar receiving the highest average score in the national trial gardens is awarded the Australian Dykes Medal. The Dykes Medal, therefore, is the highest award for an iris given by the Iris Society of Australia. The Medal is awarded by the British Iris Society and is named in honour of William Rickatson Dykes, a famous English horticulturist. The British Iris Society also presents Dykes Medals each year to iris that have been judged the best in UK and US trials.



It could be said that Tall Bearded iris that have been awarded a Dykes Medal are the best of the best. Selecting varieties for your garden that have this pedigree could reduce the risk of disappointment. Information on Australian Dykes Medal winners can be found on the Iris Society of Australia’s website.



Here is a handful of the best, selected by expert iris hybridisers and growers, John Taylor and Graeme Grosvenor: Jayceetee; Rusty Taylor; Maries Love; Boyd; Adlemi; Scared Stiff; Johnny Blue Eyes; Dancing In Pink; Our Man Buck; Delgara; Dahdah; Market Order; New Years Kiss; For One Night; Pay The Price.