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Tom Waters

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The Fertile Families of Bearded and Aril Irises


Welcome to Telperion Oasis, Tom Waters's web site devoted to the theory and practice of hybridizing bearded and arillate irises.

Since the middle of the 20th century, iris enthusiasts have been aware of the importance of chromosome configurations in iris breeding. Some configurations have limited fertility, while others constitute "fertile families" that can be developed and refined by multigenerational breeding programs.

Right: 'Goblin Orison' (Waters, 2022) OGB-/ABD

This site focuses on the six tetraploid fertile families of bearded, aril, and arilbred irises:

The 48-chromosome bearded irises, both tall and median (TTTT)

The 44- to 46-chromosome amphidiploid arilbreds, both tall and median (AATT)

The 40-chromosome amphidiploid dwarfs and medians (PPTT)

The 40- to 44-chromosome tetraploid arils (AAAA)

The 32-chromosome dwarf species Iris pumila (PPPP)

The 36- to 38-chromosome amphidiploid aril/pumila hybrids or "arilpums" (AAPP)

(For an explanation of the four-letter notation, see Chromosomes: Concepts and Terminology.)

Within each of the groups, the irises are generally fertile with each other, allowing one to breed for generations to select for new and desirable traits. Each one of these families is a reservoir of genetic potential for the irises of the future, so it is important that each include a robust range of genetic material from as many species as possible. Although most hybridizers will continue to work with the newest garden varieties in the hopes of creating improved varieties that will win the appreciation of gardeners and judges, it is also important to expand and explore the full range and potential of each family by working with lesser-used species and different approaches to combining them.

I sometimes joke that my hybridizing goal is to "make everything smaller" - arilbred medians, arilbred dwarfs, diminutive tetraploid medians, and the daintiest MDBs possible. It has often been the "little ones" in each family that have been bypassed by conventional hybridizing programs, and whose potential has been left largely untapped.

I have a video presentation that gives an overview of my hybridizing work in the six fertile families.

I hope your enjoy this website and find it interesting and informative. I welcome correspondence on all the topics presented here.


I'm afraid I have not been updating this site regularly, thanks to being very busy as president of the recently revitalized Dwarf Iris Society. Look for more updates here during the 2023 bloom season.




Tom Waters

September 2010

updated April 2023

Unless otherwise noted, all text and illustrations copyright Tom Waters and all photographs copyright Tom or Karen Waters. Please do not reproduce without permission.