Educational Article

Hybridizing, How and Why

Much of this information is useful for hybridizing all types of plants, not just irises. The basic idea is to create an entirely new plant by combining the characteristics of two different parent plants. Since we will be working with irises I will discuss the iris only.

To create a new plant you take the pollen from one plant, this is referred to as the "pollen parent", and transfer it to the stigma of another plant, this will be your "pod parent". Within a few hours the pollen grain will send a tiny tube down through the style into the ovary and then into the ovules or embryonic seeds thus fertilizing them. If the ovules are successfully fertilized within a week or so the flower will dry up and fall off and the ovary will begin to expand to form the pod. When the seeds are fully mature (in several months) this green pod will turn brown and begin to split at the tip to show the brown seeds. That is the time to harvest your seed. Even though the seeds are all from the same parents each one has come from a different pollen grain and different ovule so the resulting plants will resemble each other and be somewhat intermediate between the parents but each will be genetically different in the same manner as brothers and sisters. All the plants resulting from seeds from one pod are usually called "siblings".

But why do we want to do this in the first place? Because it's FUN! There is no high like the one you get walking down a row of flowers blooming for the first time from your cross, knowing you had a hand in planning these flowers and knowing that no one else has ever seen them bloom before. Before you reach the end of that first row you will be planning how to improve on these flowers and your next set of crosses will be underway. Some one described it as "painting with DNA". It is a creative endeavor in which almost any one can participate.

To mimic a bee all we need is a pair of tweezers, some small paper coin envelope or folded envelopes and in some cases a small camel hair watercolor brush and a small bottle of rubbing alcohol. When the pollen is ripe the stamen will split so you can see the "fluffy" pollen. If you want to save pollen for a few days to use on a later blooming flower simply remove the stamen with your tweezers and store it in a small envelope in a cool dry place. Be sure to write the name of the iris on the envelope, When the stigma begins to curl away from the style arm and looks wet it is probably receptive. Take your tweezers and remove one of the stamens from the pollen parent. Wipe it across the stigmatic lip of the pod parent, you should be able to see a coating of pollen on the sticky stigmatic lip. If pollen is plentiful place pollen on all three stigmatic lips, if you only have a little pollen you can probably still get a full pod of seeds by only pollinating one stigma. Mark your cross using small paper or plastic tags and a pencil or waterproof pen. Attach the tag below the ovary. Write the name or number of the pod parent first then an X followed by the name or number of the pollen parent. Record your cross in a note book for future reference.

Records are important!!

When working with bearded irises there is little chance of contamination by bees but when working with beardless irises it is a different story. If left alone most beardless irises will set a bee pod for every flower. To prevent contamination use "loose buds" that are about to open for the pod parent at least, I use them for the pollen parents also to be sure the pollen is not contaminated. I open the bud and remove the petals and stamens, saving the pollen if I want to use it also. By removing the petals the bees have no place to land and it is difficult for them to contaminate the cross. I then wait for an hour or two until the stigmatic lip is mature and make the cross using a fresh flower for pollen or using pollen from that saved in envelopes. If you have saved pollen, particularly that of beardless irises, it often; s scattered all over the envelope in just a few hours with non left on the stamen itself I then use a very tiny watercolor brush to apply the pollen to the stigma. If you use this method you need to carry a small bottle of rubbing alcohol to wash your brush after each cross to kill all the remaining pollen so you don't contaminate your next cross. Be sure you let your brush dry thoroughly before using it again. Luckily this only takes a minute or two. Some people are impatient and carry several brushes so they don't have to wait. If the pollen is scattered around a coin envelope you can loose much of it down in the comers so I use little folded envelopes I learned to make many years ago. If you want to make some the directions are below.

Now that we know how to make a cross the decision of what to cross is the next and most difficult task. The most important thing is to have a goal. You will be caring for these irises for the next four years before serious evaluations can be made. For the beginner you will more likely have success if you cross similar irises, pink bearded with pink bearded, Siberian with Siberian, or PCN with PCN etc. But have a reason for each cross such as a better branched pink bearded, a more ruffled white Siberian or a more hardy PCN. Select your parents carefully from the best irises available. If your goal is a better branched pink bearded iris select the very best colored and formed flower for one parent and the best branched pink available, even if the flower isn't great, for the other parent. Murphy says you will get the poor flower on the poor plant but sometimes we get lucky in this gambling game known as hybridizing.

If you think this is a hobby (read that addiction) that you want to be serious about give careful consideration to your goals. To become a top hybridizer of tall bearded irises is very difficult. The competition is stiff for beginners. However there are not many working in the field of MTB's or MDBs or working on some of the species groups or even on PCN'S. In these fields you will be able to see some realization of your goals much more quickly. Changes and improvements in Tall Bearded irises come very slowly and in tiny increments. If you are the type to be very adventuresome try some wide crosses, we really don't know what irises will cross with what. We can study genetics and make a guess but there are a lot of irises growing in our gardens that prove these genetic guesses wrong! Be prepared for a lot of empty pods but if you get a take on a wide cross and the seed grows. WOW! Whether it is a once in a while thing or a serious endeavor hybridizing is still fun. There are quite a few award winning iris out there by back yard gardeners from shot in the dark crosses so go join the addicted pollen daubers. For more information read Terry Aitken's excellent article on hybridizing in the Region 13 'Newsletter Spring 1994.

Handy Folded Envelopes

Many of you may already know how to make these handy little envelopes. I use them because when planting seed or using the pollen they can be completely unfolded so there are no hidden comers as with regular envelopes. They can be made from anything at hand if you are offered seed or pollen when you are not equipped with normal envelopes. A bit of newspaper, .an old shopping fist, I once made one from a dollar bill when offered some rare seed. It is best to use an absorbent paper such as newsprint so that seeds or pollen do not mold.

Step 1 - Use a rectangular piece of paper, 1/4 of an 8 1/2" by 11" paper is ideal (4 1/4" X 5 1/2"). Fold in along line E-F, folding A to C and B to D as in Fig 1.

Step 2 - Fold both layers together (C-A & D-B) at line I-J in Fig 2. Then fold again at line G-H to make a double fold. Crease all your folds well. Your envelope should now look like Fig 3 with a folded flap on the right side. If your paper is less than ideal in proportion you can make extra folds in this step. This will make the envelope narrower so that you can make the rest of the folds successfully.

Step 3 - Turn your envelope over so the folded flap is underneath on the right side as in Fig 4.

Step 4 - Fold corner G to J along fold line E-K as in Fig 4 and 5 and crease well.

Step 5 - Fold corner E to point K along fold line L-G and crease as in Fig 6. Unfold part way and tuck point E under the flap to as close to K as possible.

Step 6 - Complete the top of the envelope by folding H to M along fold line F-N as in Fig 6. Then tuck point F under the flap as close to N as possible. This is the same process you did in Steps 4 and 5 but from the top down. When you are finished you should have an envelope that looks like Fig 7.

Step 7 - Unfold the last two folds to open the envelope at the top as in Fig 8. Insert your seed or pollen and refold and tuck the point under the flap to close the envelope.


Contributed to the KCIS Newsletter by Carla Lankow, May 1997