The flowers that we grow in our gardens today can be roughly divided into 3 groups. Wild flowers (species), selected forms of species, and hybrids.
Tall bearded irises fall into the latter category, and hybrid ancestors of todays TB’s were around over 400 years ago. Their origins are for the most part unknown, as the iris lent itself well to travel in the dormant state and the so called “german” irises were not native to Germany.
Where the range of bearded iris species overlapped, natural hybrids were formed. Growing species in collections in gardens increased the likelihood of such natural hybridisation. The earliest known hybrids were the germanica types (I. germanica, I. florentina, I kochii, etc) Other early hybrids, incorrectly named as species, include I. amoena, I. neglecta, I. plicata, I. squalens. All of these were used in intentional and unintentional crossings with the species I. pallida, to produce new garden varieties.
350 years ago Carolus Clusius described 28 different I. germanica types, and discussed culture from seed for variation.In the early 19th century De Bure grew several hundred varieties. In France much work was done by Jaques and after his death Lemoine selected and marketed newer varieties.
Early garden varieties were mostly crosses between I. pallida and I. variegata. Their branching was tight and high, and flower size and substance were lacking.
Improvements came about in the late 1800’s when Michael Foster of England imported tetraploid species from the Middle East. I. trojana and I. cypriana, crossed with 19th century varieties produced plants with better branching, clearer colour and improved flower size and form. Later I. mesopotamica was used for more improvement of branching, but lacked cold hardiness.
Interest in breeding irises spread to the UK and USA. In the UK most breeding was by amateurs, and slowed during the war, because of the need for growing food.
In the USA nurseryman Farr imported hundreds of European and English varieties, and contributed greatly to the modern TB. Amateurs took up the cause, and the American Iris Society was founded in 1920.
The accidental appearance of tetraploid seedlings such as Dominion (1917) and Snow Flurry (1939) contributed greatly to improvement in flower form and substance, and allowed for a far greater variation in colours and patterns. All modern TB’s are tetraploid – that is, they carry 4 of each
chromosome, rather than 2 in the diploid state.
In the mid 20th century I. croatica was used to increase the hardiness of irises for growing in cooler, wetter areas.
Oncocyclus irises were crossed with TB’s by Mohr introducing yet another mix of genes and more varieties of colours and
patterns. Hybridising of tall bearded irises continues to be popular among amateur irisarians, and much progress is still being made in the introduction of new patterns, colour combinations and garden hardiness.