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Developing New Iris Varieties, (Hybridization)
- One of the pleasures I have found in gardening is
the hybridization of new Iris varieties. The first requirement for doing this is
to have a number of desirable varieties which have at least some of the traits
you would like to see in the new Iris you are hoping to develop. Some of the
best and newest varieties have been introduced to the trade and have been judged
by trained Iris judges as having superior quality. The flowers may be of a new
color or shade, a new combination of colors, superior bloom size, superior vigor
and any number of other traits. Most recently it is the ability to bloom over a
longer period or to rebloom in the fall. That extra burst of bloom after the
summer is gone is a welcome bonus. Another bonus is the presence of
additional petals or flounces or horns growing from the beards on the falls.
These may be in contrasting colors.
Dykes medal winners are good choices for planting especially those that have been introduced recently. Each year only one iris receives the Dykes medal. Usually these will be featured in magazines or online by commercial growers so obtaining them is only a problem of having enough money to purchase them and having a place to grow them. Once the plants are growing and blooming the major mental chore is deciding what plants you wish to cross to produce seed for the plants you are hoping to grow. Each parent will have different characteristics such as color, size, special features, vigor, etc. I personally love the blue flowers and although this is the color most grown and most loved there are few additional variations that can still be made to the category. At rhizome sales the first varieties to sell out are always the pinks and these have the biggest demand. The earlier pink varieties also lacked vigor and height, bloom size, and substance. So working with some of the pinks might be a good place to start. Another starting place could be working with the reblooming iris. This is an inherited trait and you won't know whether the offspring have inherited the trait until after a year or two of bloom. Another advantage to hybridizing and selecting your own varieties is that when selecting you can select only those that do well in your region of the country. It has been my experience that not all iris do well here in New Mexico especially those that are from another country such as France. Some of the varieties that grow well in California are too tender to survive here in New Mexico. So growing your own plants from seed can be a definite advantage.
Having selected the crosses you wish to make you must be able to identify the parts of the flower that are going to supply the pollen and the ovary. To the casual observer, one might think that the fuzzy beard on the falls of the flower would be the source of the pollen but that is not so. The pollen is borne on the stamen which hides under the smooth arching part that covers the source of the fuzzy beard. This also the place where one can find the style. Tear apart a couple of the flowers to learn how to identify these parts. The parts of the flower can be identified using the picture shown above. Flower parts are in threes with three standards, three falls, three styles, three stamens etc.
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Here is an Iris flower (Busy Being Blue) broken down to show the internal reproductive parts which are stamen, style arm, and ovary. Click on the picture to show it full size and in greater detail. so parts are easier to recognize. The yellow portions are the beards on the falls. The three downward broken petals are the standards. The center three heavy petals are the style arms with the stamen (white) snuggled beneath it (only one of the three is showing) Not visible is the 3 capsule ovary behind the lower standard. |
Remove one stamen from the male parent you have chosen and rub it against each of the three moist style arches (the band across the top of the style) of the female parent. If you have an early blooming male parent that you wish to cross with a later blooming female parent the pollen can be dried and saved until the female parent blooms.
You can tag the flower of the female parent so that you will not accidentally remove it when you are grooming the plant. The tag should have the date and name of the pollen parent if you are making more than a few crosses. The flower will shrivel in the next several days and the ovary at the base of the flower will begin to enlarge. Leave that bloom stalk on the plant until the capsule (pod) begins to turn brown. Then you can remove it, store it in an envelope or plant the seeds immediately. The seeds will not germinate until the following spring. The seedlings will look like tiny blades of grass and should be left in place for at least one year. Some seeds may not germinate until the second spring so do not despair. Some of the choicest flowers can come from those tardy plants.
Selecting the new varieties that you want to keep and/or share should be done with a critical eye. Every year there are hundreds of crosses made and some people dote on their own creations and name and introduce them without regard to their individual merit. This makes a very crowded listing each year and those that are not an improvement over the existing varieties are soon dropped from cultivation. Actual improvements are slow and seldom happen so don't be too anxious to have your special plants registered. Give them to your friends and let them test them out. If they really are an improvement and merit introduction their experience will be a recommendation. Otherwise, consign them to the compost pile without regrets. It was fun and that was your objective.
Not all crosses will take as some pollen may not be fertile and also some ovaries may not be fertile. Some flowers may not produce any pollen so crosses from those varieties are impossible. If you must limit the number of varieties in your garden then the infertile ones should be the first to go.
For a basic culture sheet from Cornell University Click here: http://www.ccenassau.org/hort/fact_sheets/a211_iris_culture_oct00.pdf
02/01/2009