Hybridizing Spuria Irises by Dave Niswonger
HYBRIDIZING SPURIA IRISES
As you ponder the idea of hybridizing Spuria irises
, remember that in many cases we are only six or seven-maybe eight generations from the original species; whereas, tall bearded hybridization may be as far as twenty five generations away from the species. This is said only to say that we are just beginning to explore the possibility of what may be hiding in the spuria genes we have available to us. Also, there are not many people hybridzing spurias. Only about seventeen persons have registered spurias in the last few years and on any given year, there may be only five. In 2003 there were twenty five cultivars registered.. So, the need is great and the opportunity boundless.
So, you've decided to give it a shot. The first thing you may want to do is to decide what you would like to accomplish. In what are you interested? You may simply want to improve on present cultivars. If this is so, I would suggest that you get the best available in the color and form that you like. In most cases, this will be the newer introductions but not always. Some cultivars have never been used. You might want to purchase from the Spuria Iris Society their listing of introductions and registrations which will show what cultivars have been used in the creation of certain cultivars. You can also see the parentages which will help as you make your crosses. Diversity is good. You may like the spidery form or a more blocky form. You may want to check out the branching or bud count of the cultivars you are considering. Generally, you want a form that is pleasing to the eye in good proportions. The crest over the falls can have a gap but not too much. It may fill in an open space in the bloom. The claw is the portion of the falls that connect the part hanging down with the stem. If its too long, it throws off the balance of the flower. So, short claws usually help to get better form. The color is another matter. You would want good clean colors not muddied with some other color or venation. Signals are OK and they may add to the attractiveness of the flower. Fragrance is found only in the smaller species like I. graminea
and I. kerneriana
but it would be nice if this could be added to the tall group of spurias.
It should be said that most named cultivars are in the tall group ranging from three to five feet in height. In the beginning, I would suggest that you stick with this group but later explore the small ones since they don't set seed as well and are harder to grow except for I. graminea. There is also the matter of whether they are dormant in the summer or have green foliage in the summer. Most of the older cultivars go dormant in the summer which doesn't look good in a perennial border but some of the prettiest flowers are in this group. These are usually the forty chromosome cultivars with the species background of I. orientalis
(the most vigorous and most widely grown of all the species and used mostly in the early cultivars), I. monnieri
(which maybe a hybrid from I. crocea
and I. xanthospuria
), I. crocea
(a yellow, formerly known as I. aurea
) and I. xanthospuria (commonly called ‘Turkey Yellow' which has wonderful branching). If they are grown as far north as Chicago, they may not go dormant in the summer.
Now if you wanted to work on something different, you would need to find the cultivars that may give a hint of that trait. Siberian iris breeders will say that if they can see the color in the flower, they can bring it out which is how some of the yellow Siberians have been developed. This may or not be true with spurias. You want a pink spuria so you cross two cultivars with hints of pink (an old rose color perhaps). You grow the seedlings and none of them may look like the original parents. You may make another cross with no hint of pink and a rosy hued seedling may show up. If this happens, use it with another like it and keep trying. You may cross two purples and brown shows up. Outcomes are not as predictable as with tall bearded but we haven't gone as many generations either. One of the problems too is that we don't know if we a dealing with diploids (two groups of chromosomes) or tetraploids (four groups). You might want to double the chromosomes of the smaller species (twenty chromosomes) to use with the tall ones (forty chromosomes) which would seem logical but if one is a diploid and the other a tetraploid and you grow seedlings, they may be triploids and probably sterile. But, this doesn't always happen so I wouldn't say don't try it. This is where experience is so important and when this can be shared, it helps everyone. If you cross two yellows, its pretty likely that you will get various shades of yellow and maybe gold or orange (wouldn't that be nice?). Some breeders like Jim Hedgecock, are interested in ‘dark tops' as in tall bearded breeding (or you may wish to call them reverse amoenas) but this is another color pattern of interest if you can get larger sized standards.
Branching in spurias is usually considered to be serpentine (snakelike) but seedlings from I. notha can have zigzag or candelabra branching. The spathes from this background can have different shades of green making an interesting contrast. The blue color from I notha
and I. demetrii
will not fade which often happens with blues. One of the problems here is often these hybrids are not very fertile. I. xanthospuria
can also produce a more of a zigzag branching.
When working for summer green foliage, some of the species that will provide this are I. demetrii (as in ‘Missouri Springs') and I. notha (one of the latest to bloom) (examples are ‘Gasconade River'
, ‘Eleven Point River'
and ‘Whitewater River'
) that have thirty eight chromosomes and I. carthalinae
(one of the earliest to bloom with a good bud count) and I. klattii
.These have forty four chromosomes. Some taxonomists feel that I. klattii
and I. musulmanica
are the same but this writer has grown seedlings from both and feels that they are not the same. I. klattii
seedlings will bloom a week earlier than most tall spurias. They will also have more hybrid vigor, growing a foot taller and making more increases. Examples of this are ‘Russian Blue'
and ‘Russian White'
. You can see that hybrids from these can have forty or forty two chromosomes which may help in deciding which ones to cross with each other.
Another possible goal to consider would be to develop a smaller spuria. Florists who get to know them, really like them; but, somtimes they are too large. This is where you may want to turn to the smaller species which may not be easy. Species usually have very strict requirements (not I. orientalis). Some originated in marshy areas like I. carthaliniea
whereas, others grow in fairly dry conditions, like I. demetrii
Creating hybrids seems to broaden the base of adaptability. Ben Hager used to say that you may make many crosses and not get any seed but if you finally get just one seed and it grows, it is usually fertile and you have new genetic material with which to work.
Some of the smaller spurias in existance are ‘Highline Snowflake'
1991) coming from an I. halophila
seedling and ‘Ruffled Canary'
1970) (this has I. xanthospuria in the background and although parentage records are not complete it looks like it could have I. halophila in I too); ‘Pieces of Eight'
) is from I. maritima and ‘Ruffled Canary' again; ‘Maritima Gem' (Hager1990) from ‘Clarke Cosgrove' (the name sake is a past President of the Spuria Iris Society as well as a Past President of AIS) crossed with I. maritima. Charles Jenkins got several nice small ones from this but lost them all. Charles has others on the small side such as ‘Doris Irene'1900, a vibrant blue from I. musulmanica, ‘Amand a's Eyes' 1900 which is out of I. halophila, a pale blue with ivory shading in the falls, and ‘Elfin Sunshine' 1998 a pale yellow, also
out of I. halophila and the first of the tall ones to bloom. Other small ones of Jenkins' seem to appear from larger parents such as: ‘Tiny Lou' 1990 from ‘Protege' and ‘Dawn Candle', ‘Little Frills' 1998 from ‘Color Focus' 1990 selfed and ‘Little Splash' 1997, a creamy yellow with a large splash of yellow in the falls but does have I. xanthospuria in the background through ‘Elixir' (Hager 1964), ‘Minitrend' 1997 has ‘Color Focus' in the background which goes back to ‘Ila Crawford' (Hager1976). According to Eric Tankesley-Clarke from Adamgrove, Ben Hager had some small seedlings from ‘Ila Crawford' background. As mentioned, Ben Hager used I. maritima, I. carthalinae, and I. demetrii as well as ‘Protégé' (HagerâTM
69) which is out of I. carthalinae (also, ‘Neophyte' 1964 which has summer green foliage as well). Ben crossed ‘Protege' with I. klattii and got some small ones from that cross too. Its interesting to note that the species mentioned are all from the tall group with I. halophia, I. carthalinae, I. musulmanica and I. klattii all having 44 chromosomes. I. demetrii and I. maritima having 38 chromosomes and I. xanthospuria with 40 chromosomes. Dr. James W. Waddick in an article titled as "The State of Spuria Irises" (AIS Bulletin Vol. LXXXV, No. 3, July 2004 pages 82 to 86) suggests that hybridizers should be using some of the smaller species such as I. graminea (34 chromosomes), I kerneriana ( 18 chromosomes) and I. sintenissii (16 chromosomes--Simonet counted 32 in a tetraploid form of it). This is food for thought. Botanists and taxonomists can not agree as to how many species there are but the writer feels there are about sixteen which gives the hybridizer a great selection from which to choose. Look for seed offered by SIGNA and the British Iris Society.
Oleg Amekhin from the Ukraine has crossed I. haliphila with I. graminea and he says the results were not very good. The stalks were about 40-50 cms (1.5 ft.) and the flowers were a dirty blue. He says these hybrids were 100% sterile which is understandable to some degree when you consider a 44 chromosome species crossed with a 34 chromosome species would give you a 39 chromosome hybrid and the odd number of chromosomes would make it difficult to connect half of them with something else. But, this writer wouldn't say not to try it. Amekhin got earliness in a hybrid from crossing I. klattii with I. sogdiana (This is 44 ch. crossed with ??? , if sogdiana is a subspecies of I. notha it would be 38 ch. which would give a hybrid of 41 which is unlikely but if a subspecies of I. spuria grouped with I. halophila it would be 44 which is more likely). From this cross there was an interesting blue with a nice stalk about 3 feet tall and a light purple with cream colored style arms. The latter, he registered as ‘Gratsiya' in 1996.
The writer has grown I. graminea and I sintenissii but was unable to make any crosses with them. He has tried to grow I. kerneriana from seed several times and did not come up with any plants. Berney Baughen from England has had success growing this yellow with strongly recurved falls. He says I. kerneriana usually has two flowers per stem flowering above narrow green foliage and takes 3 to 4 years to form into neat compact clumps. The roots are shallow and resent disturbance but can be moved if careful to bring enough soil with it . The writer had thought that this might be a good one to double the chromosomes giving 36 chromosomes which when crossed with a 44 ch species a 40 chromosome hybrid could be achieved.
Doubling chromosomes on spurias may be difficult since its harder to control germination of the seed as compared to others. It might be that if the seed could be picked green, just as the seed pod is starting to crack, sterilizing them with a chlorine solution and storing in a refrigerator in a Petri dish between dampened filter paper, that germination would occur in a couple of months or so--then soaking them in a solution of cholchicine, Treflan or Surflan just as the seed start to split (germinate) then rinsing extremely well, doubling might be achieved.
Again working with the smaller species may pay off big but this writer doesn't think it will be easy. He has tried to grow I. pontica several times but has never gotten plants. He has been growing I. machowii for three years and hasn't gotten it to bloom and the same with I. ludwigii (it and I. pontica are good for rock gardens since the bloom is close to the ground and the foliage is its best asset). I. pontica is normally in the blue-purple range of colors, sometimes a rosy violet,but Michael Diev from Moscow and Berney Baughen from England, had yellow forms appear in their seedlings but I think both of growers have lost them now but that's an indication of the possibilities. Its the shortest, along with I. ludwigii, growing 2 inches high but having the most chromosomes of all with 72.
Most beardless irises can be pollinated very easily by insects since the stigmatic lip is so close to the falls. Bumble bees especially, like spurias, and when they go down into the flower for nectar their back is covered with pollen which dusts the stigma. In order to prevent this, pull off the falls just as the flower is about to open and the bee has no landing field.. Generally, the stigmatic lip is not receptive to pollen until the second day from opening. If the weather is hot and dry, you could pollinate the first day and again on the second day. Although most spurias have no fragrance, there will be lots of insects, wasps and bees around spurias. This is because bubbles of nectar form on the outside of the ovary at the base of the flower, its like syrup, just take your finger remove some and you will see its delicious. I. lactea also does this but you will have to cut the flowers and take into the house to see it since the insects keep it clean. Because of this, Dr. Rodionenko thinks I. lactea is close to I. spuria and crosses can be made. Charles Jenkins has tried this and may have some interesting results but the seed he has sent me showed no signs of a hybrid. I. lactea sets seed so easily--its almost as if pollen flying through the air can find the stigmatic lip even though the falls have been removed. The chromosome count is not known so various counts of chromosomes of spurias could be used to see which might work. Dr. Rodionenko thinks I. xiphium would cross with spurias even though it is bulbous. These are Dutch irises. I xiphium has a 34 chromosome count which might work with I. graminea. But many Dutch irises are hybrids between I. xiphium and I. tingitana which has counts of 28 and 42 and also possibly with I. latifolia with a count of 42. So, the hybrids of Dutch irises could range between 28 and 42 but if you had one with a 38 count it might cross with some of the 38 chromosome spurias. There are lots of possiblities in the hybidization of spuria irises.
Now getting back to the pollination, when you have completed the cross, tie a tag on it listing the seed parent first. When the seed pod matures, pick it as the pod starts to crack open. You will find very light in weight seed that the wind could almost blow away. The color of the seed will range from white, ivory, pink to almost black. The writer has found, though not a scientific study, that the lighter colored seed produce like colored flowers and the dark colored seed, darker colors. If you plant the seed immediately, it will germinate before winter and grow about one inch tall in Missouri. If the temperature drops to zero F in your area, you might put on a light mulch but not too heavy as to smother the seedlings. Then remove it in early spring. This will give them a head start and when they reach 3 to 4 inches high you can transplant them. If you grow the seed in a greenhouse, you may have a damping off problem. If this is the case use some Terrachlor in the soil of pot. Spurias are very susceptible to mustard fungus so you may want to put some terrachlor in the row when planting them. A 10% granulated form may be obtained from Union Carbide Co. which indicates iris on the label. This is an easy way to use it in the granulated form. If you plant them before the tall bearded bloom, many will flower the following year. Use a fertilizer in your water preferably one that has a root stimulator in it when you transplant them. In the row sprinkle some 14-14-14 Osmocote or slow release fertilizer and some alfalfa pellets which have a growth stimulant in them. If you don't plant the seed when they are green and they go dormant you would plant them in the fall. They may not germinate the following spring so you would leave them there for another year. Some of them may germinate and you could plant them or wait another year. Growers in the southwest U.S. and California might want to wait until fall to transplant them just when they are transplanting mature plants. They would grow all winter long and bloom the next spring. The writer has had some seed that took four years to germinate. So, plant the seed in a place that you can leave for at least two years. Pots as well as a seed bed can be used to germinate the seeds. Seed will last for several years; therefore, if you don't get them planted, save them for another year. It may take a couple of years for the plants to bloom and even three if you live in the north.
-- Main.RPries - 2010-07-06