Starting the Dahlia Season forum: Spacing plants for pollinating

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Pline
Jun 6, 2020 11:44 AM CST
I don't know if this is the right spot for this question, but here goes--
I'm trying hybridizing for the first time this year. I'm going to try hand pollinating, but also rely on the bees. To make it easy for them, I've heard you should place the two varieties you want to cross pollinate close together, but how close? Should they be in the same hole when I plant them?

Thanks
Imageteddahlia
Jun 6, 2020 12:20 PM CST
Name: Ted
Oregon
We enjoy breeding new dahlias!
Should they be in the same hole when I plant them?
There is concept called an "isolation bed" and it was developed and used by the late Mike Iler of Blossom Gulch Dahlias. The idea is to select several varieties that could be crossed together because of their type and Mike liked to use form as his criteria. For example, he had an incurved cactus bed of dahlias that had about 30-40 plants of of probably 10 or so varieties in it. The bed was at least 50 feet away from his other dahlias. The bees that would work the flowers would stay in this bed and pollinate the incurved cactus with the incurved cactus. The reason he used about 10 varieties was that he had to make sure that he had some known seed producers in there to assure that he would get some seeds. Most of the incurved cactus types do not make many, if any, seeds. However, all of them produce some pollen. His isolation beds worked very well.

The Boleys(Sandia Dahlias, SB varieties) who grow on an acreage in Washington state are also isolation breeders. The have a very large grassy field and have numerous isolation beds separated by about 50 feet. They have a waterlily bed and I believe a Pom bed and others.

The simplest thing a backyard breeder can do is to plant similar types of flowers together and the bees will generally pollinate "serially" meaning that they will go down a row from plant to plant and will not bring in much pollen from plants a row or two away.

Gordie Leroux of Kenora Dahlias used a different method to encourage bees to use the correct pollen. He picked bouquets of the correct pollen flowers and placed them by the plants too be pollinated. AND he removed all the other flowers. from everywhere else. The bees were stuck using the pollen he provided. This method has not been done by anyone that I know of and deserves to be replicated.

Hand crossing is the ultimate breeding technique and can achieve results when all other methods fail. However, It is so time consuming and generally disappointing in that most crosses do not make seeds. that nearly everybody who has done it reverts back to isolation breeding above. Having said that, there are many crosses that bees NEVER make that can be done. Bees for example seldom pollinate poms as they are so small and have such little pollen that they cannot get to the pollen in there and ignore the pom flowers. My wife hand pollinated a pom and got 20 seeds. and all the bee pollinated poms yielded almost no seeds at all. Giant flowers too are candidates for hand crossing as they have so few flowers that the odds of pollen being available from another giant flower blooming at the right time are not good. If a bee pollinates a giant, the pollen comes from a smaller flower.

“Flowers are like friends; They bring color to your world.” – Unknown
[Last edited Jun 6, 2020 12:31 PM CST]
Quote | Post #1348327 (2)
SteveM
Jun 6, 2020 1:15 PM CST
Name: Steve
San Diego
Commercial cut flower grower
Paul Comstock also used the 'isolation' method. He grew on about 1/2-1 acre of land and had a separate structure built for his desired crosses. It was (from memory) about 20X20 feet and was enclosed with 'bee-proof' fabric on all sides and the top. It wasn't shade cloth, and now I wish I had paid more attention, but it was 1984, and I thought I had already learned everything about growing dahlias. Paul wouldn't save any seedling that was smaller than about 8" in diameter. Ironically, his most successful introduction, "Edna C", was headed for the compost heap (because the bloom was too small) when his wife Edna ( a great dahlia grower, maybe better than Paul) convinced him to keep it.

Bill McClaren used the 'bees go down one row' method. (and sometimes hand pollinated) He would spend his weeding breaks watching the pattern bees followed. He hybridized mostly open-centered varieties. The bees always followed the most efficient path and never diverted from a row unless the next plant in line had no pollen.

Imageteddahlia
Jun 6, 2020 1:59 PM CST
Name: Ted
Oregon
We enjoy breeding new dahlias!
The most common "rookie" mistake is trying to pollinate a variety that does not make seeds. And when hand crossing even a variety that makes seeds, it may not be compatible with the pollen parent you are using. So if hand pollinating use a couple three pollen parents if possible. Hand pollinating is not for the faint of heart as lots of work can produce little results but if you hit a home run it may well be something that could not be achieved by using bees. I personally tried it(my wife Margaret did almost all of it) about 8 or 10 times. The crosses were well planned out and executed well. One seedling from my crosses produced a medal winning giant dahlia. All the rest of the crosses produced either no seeds or seeds that did not sprout. I found the work to be too demanding for my attention span and let Margaret do it. She finally lost interest when she added up the over 100 hours of work and the few seeds that resulted. It is physically demanding too as the mother plants are located all over the garden and it takes lots of walking to do the rounds(you need to do the cross 3 or 4 times). . Again, you can achieve results that cannot duplicated by other methods but the time and frustration involved are monumental.

“Flowers are like friends; They bring color to your world.” – Unknown
ImageDillyDahlia
Jun 10, 2020 7:45 PM CST
Name: TJ
NY Zone 6a
Flower Power!
Steve and Ted, Thank you for the awesome information! Super interesting and very helpful.
Pline
Jun 11, 2020 6:25 PM CST
Thanks for the info! After reading your posts, I dug up most of my dahlias and rearranged them in bee friendly rows. I'm amazed at how much there is to know about dahlias
Imageteddahlia
Jun 23, 2020 8:40 AM CST
Name: Ted
Oregon
We enjoy breeding new dahlias!
One thing that is a shock to new dahlia breeders is the inconsistency of the seedlings even from hand crossed flowers. Blame it on the octaploid chromosomes. Too many genes at too many locations means the wrong ones appear all the time. The method that works to get around this variation is to pull the handle on the slot machine more times, meaning plant more seedlings. Hand crossed seedlings are in my estimation only about 30% better than bee pollinated plants from isolation beds. However, as I have stated before there are crosses that bees NEVER do and they are the ones that people do want. So if we were to do some more hand crossing, we would probably concentrate on those crosses. Another advantage to hand crosses is absolutely knowing the identity of both seed parents. This is important if you are trying to increase the percentage of genes from a well bred flower into your line.
“Flowers are like friends; They bring color to your world.” – Unknown

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