Long Crosses - or - Welcome to my TET Talk

 I have been struggling to figure out how to begin this. What is a long cross? Who cares about weird inter-species cross breeding of irises? Why do I care? And what does this have to do with a TET talk? 

Five years ago, when we restarted the garden, I stumbled onto the local rock garden group (NARGS is the national org)... and folks quickly pointed me in the direction of the annual seed exchange. It didnt take five minutes on the SeedEx page before I was lost like a kid in a candy store. I mean, read through the list! It's exhaustive! And someone collected those seeds and donated them to the SeedEx. 

Seeds are magical. Every bit of hope and wonder are encapsulated in every single seed. When those seeds have even the tiniest pedigree, there's a story. The seeds came from somewhere. Someone grew them, collected them in the wild, shared them from a family member's garden... on and on. There's a story.  I was hooked.

The first year I ordered seeds from NARGS, it was primarily perennials that I thought might do well being winter-sown. Seeds like poppies, columbine, digitalis, and lupines. Seeds that I now think of as being fantastic 'starter seeds' or 'gateway seeds'. They are easy to start, easy to grow, easy to transplant and they produce copious seeds so you can share your seeds with others. It's a gateway drug.

Before long, I had found out about the SIGNA iris seed exchange. Starting a new garden means needing lots of plants... and being short on money and long on patience, I figured growing irises from seed would be fun. In the first year of seedlings, I learned a ton. The second year was akin to jumping from kindergarten to middle school. Some plants definitely wanted my lunch money. Here we are a few years along and it feels like I took a wrong turn in college. What would life have been like if I had discovered how magical plants are, thirty-five years ago? No time like the present! There is so much to learn. I mean sure... you stick a seed into dirt, stand back and watch, right? Well... kind of. But that's just a tiny bit of the story.

Much like if you tell someone you like to knit, they will immediately tell you their favorite yarn, favorite yarn store and suggest you try their favorite pattern... and two minutes later you're fast friends... if you tell someone you save seeds, something similar happens. It is a strange fellowship. I feel like I should have t-shirts made up. "Got Pollen" written across the back. It is true though. Once you start planting seeds, it is a quick step and a jump to crossing varieties. Maybe you start with tomatoes or peppers, or maybe you start with zinnias and cosmos. It takes a tiny effort to bring that pollen to another flower and POOF! You're a bee. Next spring, you're amazing!

One of the things I quickly learned is that there not only is a secret handshake among seed-savers, but there is a secret code. Each family of plants has its secret code that means something mystical. Peruse any seed catalog in the winter months and you'll see: F1 hybrid.

from: https://img.freepik.com/premium-photo/f1-racer-driving-formula-car-fuel-car-professional-racing-competition-wallpaper-background_917506-133242.jpg 

This is NOT the F1 hybrid I am talking about.

I am talking about those tomatoes like: Celebrity F1, Big Beef F1, Sungold F1 (cherry), Sakura F1, Mountain Magic F1, Early Girl F1, Better Boy F1, Supersweet 100 F1 (notice the F1 in the name?). Okay, I will admit it... I had no clue what the heck "F1" meant thirty years ago when I first opened a seed catalog. All I knew was that the seeds were more expensive and usually fewer in a packet. 

"‘F1’ means ‘first filial generation’, and indicates the first generation produced from the parental cross."- from https://hub.suttons.co.uk. F1 were first generation seeds... meaning that they had hybrid vigor... and in many cases they had stronger resistance against viruses and other pathogens. Oftentimes they were sterile (although, I learned through experimentation, those seeds saved from F1 hybrids were now something completely different). Tomatoes, peppers, squash and the like, attract so many pollinators that unless you are growing a field of only one variety, you are doomed to having varieties cross-pollinate. Could be a good cross, might be a dud. 

Genetics is weird stuff. I dont profess to understand genetics well enough to teach it. I can barely get it into my head sideways, with a not-so-gentle push. 

Turns out that F1 hybrids aren't that special... unless you are selling seeds on a commercial level. If you want seed stability, you want far more generational stability. That leads to F2, F3 and so on. None of this was particularly relevant until I became interested in hybridizing irises (and some other stuff I wont delve into today). 

What's a hybrid iris? 

Most folks who grow irises are familiar with tall bearded irises. On my first visit to my local iris club, I found that nearly everyone grew tall bearded (TB) irises. They talked about them as though they were a species. Nope. They are a complex hybrid of many species. 

From chatGPT: Genetic studies confirm that modern TB irises are overwhelmingly derived from I. pallida × I. variegata, with additional introgression from the tall Near Eastern species (mesopotamica, trojana, cypriana, kashmiriana).

Why is this important to know? 

There's the science, the history, the cultural knowledge, and the curiosity (and more!) in knowing about where these irises come from. 

I grow primarily beard-less irises like Siberian irises, iris ensata (also called Japanese irises), iris laevigata, iris pseudata, iris lactea, and a whole host of other hybrids and species irises. Which leads to the question: how do you know if it is a species iris or a hybrid? For most gardeners, buying their irises from garden centers, nurseries and the like, you'll be finding hybrids. Named varieties, created by, you guessed it: hybridizers!

Take for example Siberian irises. Not from Siberia. In fact, iris sibirica (and iris sanguinea) are found in pockets all over "Europe (including France, Italy, Switzerland, Austria, Czech Republic, Slovakia, Germany, Hungary, Poland, Romania, Bulgaria, Former Yugoslavia, Belarus, Estonia, Latvia, Lithuania, Moldova, Ukraine and northern Turkey) and Central Asia (including Armenia, Azerbaijan and Siberia)." -https://en.wikipedia.org/wiki/Iris_sibirica   

As a hybrid group, Siberian irises are very cold-tolerant, easy to grow, and relatively care-free.  What is interesting to me is that it took combining iris sibirica and iris sanguinea both in the wild and through hybridizers, to create the earliest Siberian irises that were grown in gardens in Europe. It is incredible to me that this was happening as far back as the Middle Ages! 

Siberian iris 'Shaker's Prayer' (Carol Warner)

Siberian irises have two distinct groups based on chromosome count. The 28 chromosome group is comprised of iris sibirica, iris sanguinea and iris typhifolia. The 40 chromosome group is a whole other kettle of fish to be saved for another day's writing. 

Why all this preamble? Well, once I started growing Siberian irises in my garden, I was smitten. I loved the range of colors and forms! And when the blooming season was done, there was a very graceful grass-like plant remaining behind that needed no tending to. What more could you ask for in a flowering perennial?  This led me to ordering a few plants online. They arrived and again, I was met with abbreviations that didnt make sense immediately. 

The new abbreviation was (Tet).  Thankfully smart phones in the garden are a thing. Tet was short for tetraploid.... which is another way of saying that the iris has 2x more chromosomes than diploid varieties. 2n=28 (diploid) vs 2n=56 (tetraploid). At first, I couldn't figure out why that was meaningful. It wasn't until the second year of growing these tet Siberian irises that I saw what gave them their appeal. They had thicker stems, more substantial flowers, slightly richer coloration, and generally seemed a bit more pumped up. It took a bit of reading to come to the understanding that in doubling those chromosomes, everything sort of doubled within the plant. In the best circumstances, it made flowers that were spectacular (see some of Currier McEwen's or Dean Cole's Siberian irises!).

What I didn't know was that diploid and tetraploid Siberian irises don't cross-pollinate readily. When the crosses do take, they most often result in sterile offspring with a 2n=42 and are triploid. What this meant in my garden was that if I wanted to play Who's Your Pollen Daddy? with Siberian irises, I had to separate the diploid varieties from the tetraploid varieties for the purposes of crossing.  This meant moving a fairly decent number of plants around the garden and into the hybridizing beds I was beginning to build. 

Fast forward a few years and I am finding new reasons to mess about with tetraploid Siberian irises. From some of my reading, I have found that "long crosses" are possible... meaning that you can create a cross-species pollination, with some species and the seeds can produce new hybrids. Yay. In many cases, they are sterile because of the mis-match in chromosomes between the species. Where it gets a little wild is when you introduce tetraploidy. If the chromosomes are doubled, sometimes the number of chromosomes available in the cross are more closely aligned, and the cross will take. 

I have not proven this in any way yet, so from a practical perspective, this is all new to me. What it means in the garden is that my tetraploid irises are going to get a workout this coming spring! I hope to create a long-cross program using plants that seem to be willing to cross with just about any other iris. One of these irises is iris versicolor (also known as Blue Flag). I have in mind some very interesting crosses planned, but I will save that for another post. 

 

Both images above are iris versicolor, which comes in a huge array of colors and forms.