Using Species in MDB Breeding, Part 2: Iris aphylla x Iris pumila

 by Tom Waters

This is the second of three posts on my experimenting with various species in breeding miniature dwarf bearded (MDB) irises. Here’s a quick recap: Most MDBs today are small selections created when breeding standard dwarf bearded (SDB) irises. I think there is value in creating a line of true-breeding MDBs: fertile plants that are MDB-sized and consistently produce MDB-sized offspring. Ideally, such a line would be compatible with SDBs (and MDBs from SDB breeding), so one could use all the wonderfully developed modern MDB and SDB cultivars.

Certain dwarf species and combinations of species are compatible with SDBs in terms of their chromosome configuration. One such species is Iris lutescens, and in part 1 I described my work with this species to date. In this post, I look at hybrids from I. aphylla x I. pumila and their usefulness in MDB breeding.

I. aphylla crossed with I. pumila produces fertile hybrids having a chromosome configuration that is compatible with SDBs. The MDB ‘Velvet Toy’ (Dunbar, 1972) is an early example of such a hybrid. We might also include Ben Hager’s MDBs from his aphylla-derived MTBs crossed with I. pumila as another variation on this basic type, although the MTBs have tall bearded and border bearded ancestry as well as I. aphylla.

S006-01
 I. aphylla x I. pumila

My own aphylla x pumila seedling, S006-01, is an interesting little plant. The flowers are purple and not particularly distinctive, but the plant is quite small, at around five inches in height. It also has a unique branching pattern. It has basal branching inherited from I. aphylla. The branch and the main stem are of equal height, and each is topped with a double-budded socket. The four buds open successively, so there is only one flower open at a time. This seems to me a very desirable trait to introduce into MDBs, but so far none of its seedlings have inherited it.

I have bloomed a number of seedlings from SDB ‘Eye of theTiger’ (Black, 2008) X S006-01. They were a carnival of different colors and patterns, but unfortunately, none had the daintiness I was looking for. This spring, seven years after I made the cross, a straggler bloomed that seems genuinely small and MDB-sized. I will keep an eye on it in coming seasons.

S028-44
Eye of the Tiger X S006-01

Realizing that I probably should be crossing this seedling with small MDBs rather than SDBs, I used ‘Dollop of Cream’ (Black, 2006) and ‘Icon’ (Keppel, 2008) for the next round.

The ‘Dollop of Cream’ seedlings had fairly nice form, some blue, some white. They bloomed near the boundary of the MDB and SDB classes, but I am hoping they may settle out on the smaller side when grown in normal garden conditions. I kept a blue one with small flowers to evaluate further.

Seedlings from 'Dollop of Cream' X S006-01

The ‘Icon’ seedlings are more exciting color-wise, in various shades of orchid with deeply saturated spot patterns and dark blue beards. I describe the color as “juicy”. Sadly, they produced hardly any pollen, and I couldn’t really test them as pod parents because they bloom earlier than anything else except the pure I. pumilas. I did get a scant 8 seeds from sib-crossing two of them, so we shall see. Again, height is rather marginal, near the boundary between MDBs and SDBs. I’m keeping them all in hopes that they may produce more pollen in the future.

Icon X S006-01

I do believe my I. aphylla x I. pumila seedling has the potential to bring me toward my goal of a line of true-breeding MDBs. I have seeds from it crossed with ‘Self Evident’ (Hager, 1997) and ‘Miniseries’ (Keppel, 2011).  And it will also be interesting to take this one more generation further and see what emerges.