FAQ: Hybridizing Dahlias- Basics

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Table of contents
» What is 'hybridizing' all about?
» Hybridizing Philosophies
» Choosing a hybridizing goal
» Maintaining records of seedling lineage
» Techniques for controlled pollination
» Extending pod maturation time
» Harvesting seed
» Buying Seed
» Storing seed
» Sprouting the seeds
» planting out seedlings (spacing, plant height, pinching)
» Defective Seeds
» Bloom analysis/culling & keeping
» Digging Seedlings
» Introducing seedlings/ time schedule
» Hybridizer Stories
» Misc. topics
» General comments for Hybridizing FAQs
» Naming seedlings & sports

What is 'hybridizing' all about?
This is an advanced topic designed to assist dahlia growers in creating an action plan for their breeding goals.

"Hybridization is the process of crossing two genetically different individuals to result in a third individual with a different, often preferred, set of traits. " -Plant of Life

In other words, 'boy' flower meets 'girl' flower, and seeds happen. A hybridizer is a person that actively plans the traits of the resulting seedlings.

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Hybridizing Philosophies
There are different levels of thought that goes into hybridizing dahlias, from haphazard and casual to systematic and goal-orientated. However you choose to hybridize, it is important to understand the differences.

The most haphazard and casual hybridizers:
-grow any variety they like, with no regard for future seedling traits
-are happy with most seedlings, and have a hard time culling any
-sometimes luck out with a jackpot seedling

The most systematic and goal-orientated hybridizers:
-carefully consider which varieties they want bred together, and encourage pollination between those varieties
-keep careful records of both parents for many generations back, often using numbered seedlings in the breeding program
-choose parents based on what traits they are looking for in future seedlings
-cull most of the seedlings, keeping only a small percentage that show promise of their goal
-are more likely to produce quality seedlings that are desirable to other growers

This FAQ is intended to introduce aspiring dahlia hybridizers to techniques that will increase your chances of producing seedlings that the most avid dahlia collector will want to grow.

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Choosing a hybridizing goal
Are you wanting to brighten up your landscape with wild and wonderful open-center surprises ? Good news, that will happen with most of your seedlings if you have any collarettes in your garden.

Are you wanting to produce big dahlias? Cross only B's, A's and AA's, and have lots of patience.

Are you wanting a strong purple? Cross other strong purples with each other, or whites, and have lots of patience.

Often goals in hybridization are only met after years of cross-breeding similar traits together until color, form, vigor and tuber durability all align in the perfect seedling. Having a specific goal and successfully working toward it can be the most satisfying part of hybridization. If you want show-quality seedlings or a specific trait, then there are choices to be made on what varieties you wish to include in your breeding program.

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Maintaining records of seedling lineage
teddahlia wrote:Record keeping: One believes that "you cannot forget" but we all forget. Keep some records of your seedlings. We always kept records of the ones we mark to keep. I wish I had kept more records about what we did not keep too. In other words if you plant 20 seedlings of Jim's Alabaster and kept none of the seedlings, that would be good information to have and will prevent you from planting another 20 seedlings of it next year. Since we recorded only good ones, we eventually identified the better seed parents and crosses but probably grew some seeds from poor parents a bit too long. Our record keeping is pretty simple: We have a spreadsheet for each year. It lists the ones we identify to keep only. Each seedling is assigned a number with the first two digits the year and then the number of the selection. 13-87 was grown in 2013 and it was the 87th one marked that year.The next fields are the classification, B IC DK RD. The next field is the parentage: Augustina(it used to have both parents like Augustina x Cotton Candy when Margaret did more hand crosses). The last field is remarks and the good and bad and other things are stated here: fades a bit, form excellent, Margaret likes, stems iffy, Best, or cut flower. If I want to find it again in the garden, I often list it's location Row 4, 10 feet. We keep the blank spreadsheet in the garden in a waterproof clipboard. I bring it into the house once in a while to add the data to the computer(More recently I have been taking a picture of it as I take pictures of the seedlings).

Ken Stock of Bournemouth, England, who is in very poor health now, used to immediately name his best seedlings. He said that made it easier to remember them. We seldom if ever name any of them. It would not work here as Margaret seems to take years to agree to any dahlia name.

And pictures really help. You need to mark the pictures with the number of the seedling as soon as you download them to your computer. I have hundreds of pictures of unknown seedlings as I forget to do this step. I do not try to take pictures of all of them. It is more important to mark the good ones with flagging tape than taking it's picture. We are often in hurry, and when you see a good one, mark it immediately with marking tape even if you do not have time to record it into the spreadsheet. And flagging tape, needs to be attached at the bottom of the stalk a couple of inches off the ground. If you just mark a flower, it will eventually fall off. If you have time, write something on the marking tape. Ideally, we list the the same data as the spreadsheet on it. Every year when we dig the first year seedlings we find flagging tape on a seedling that was not entered onto the spreadsheet. If the there is nothing written on the flagging tape, it is saved but the only info on the seedling is the parent on the tag next to the plant. We plant several of these second year unknowns every year.

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Techniques for controlled pollination
There are two main techniques used by hybridizers to control what dahlia varieties pollinate seed parents:

1. Narrow the choices down for the bees, grouping the varieties you most want paired
You can group the chosen varieties by using distance to buffer the intermingling of pollen (preferably fifty feet or more) or bee tunnels made of shade cloth (encourages bees to go down an entire row instead of skipping around the whole garden)

2. Hand pollinate, choosing the pollen parent and seed parent
Brush the pollen-laden male bloom into the open stigmas of the receiving bloom. Be sure to protect both blooms prior to pollination and the mother bloom afterwards from bees and other pollinating insects, and record each of the parents so you know that information when you collect the seeds.

Read detailed information on these techniques here: http://cubits.org/Dahlias/thread/view/82116/

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Extending pod maturation time
Extending pod maturation time

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Harvesting seed
Harvesting seed
Dahlias in the wild create seed pods that dry and then shatter, spreading the seeds over a wide area. When we harvest dahlia seeds it is impractical to allow the seed pods to reach the stage where they are completely dry and are in the process of shattering. The goal of seed collecting is the gathering of seeds that will sprout into seedlings. Dahlia seeds undergo a ripening process in the seed pod. One way to measure the ripeness of a seed is to observe the color of the seed. The seeds start out as white and darken to tan, then to brown and then a very dark brown. Some dahlia seeds do ripen to a deep black but ripe seeds can be very dark brown, dark gray or dark black. In many climates, the cooler weather and rain in the latter part of the growing season allow considerable rot in the seed pods. In those conditions it is rare to see a seed pod ripen on the plant to the "shattering" stage. Most of us have these growing conditions. So in order to successfully gather seeds, you need to harvest the seeds at the point when the seeds are viable and will sprout but before they have suffered the ill effects of rot. Experienced seed gatherers, can examine a seed pod on the plant and can estimate whether the seeds are mature and ready to be harvested. The first step is to recognize the outward signs of a ripe dahlia seed pod. After the pollen is no longer visible in the center of the pod. it begins to ripen. At his stage the pods are soft to the touch. As they ripen, they become more solid and there are three good indicators to identify ripe pods and seeds. First the seed pod changes color from green to a tannish color. This change in color is not consistent among dahlia varieties as many ripe see pods remain somewhat green. The second indicator is the pollen at the tip of the seed pod. A ripe seed pod will show black remnants of the pollen at the tip and if a seed pod has dark black pollen and is very solid to the touch, it is likely that the seed pod is ripe enough to pick. The last indicator is visual inspection of the seeds within the pod while they are still on the plant. The pod can be gently opened and the seeds palpitated with your fingers. Ripe seeds are very firm and sharp and can easily felt. If you feel the seeds, you can then open up the pod enough to inspect the color of the seeds. If they are dark brown or black, they are ready to harvest. If conditions are poor in the field, you may want to harvest a seed pod that has both ripe and unripe seeds in it as the seeds do not all ripen at the same time. If you wait to harvest that pod, it may rot and you would lose all the seeds.

Most dahlia seed gatherers, shuck the seeds from the pods within a day or two of harvest. This is because some of the pods are partially rotten and will continue to rot if the seeds are not removed immediately. There are people who prefer to ripen the seed pods indoors by one of two methods. Some people place the seed pods with long stems into a vase as though they were flowers. The stems are in water and the waster changed regularly until the pod is completely ripe. The other method is to allow the pods to dry without any water. Typically, a sheaf of pods of the same variety is tied together and dried in a dry room or greenhouse. Some people hang them upside down. In either case, care must be taken to gather the seeds when they shatter from the pods.

Germination rates: certainly the seeds that are carefully ripened will have a somewhat higher germination rate than those that are taken from more immature pods. However, most breeders do not ripen the pods after harvest as there can be considerable rot and the benefit of riper seeds is offset by the loss of the seeds to rot. They say that lower germination rates are very acceptable to them as all they have to do to overcome that deficit is to plant more seeds to get the desired number of seedlings. The goal of gathering dahlia seeds is not germination rates but rather seedlings that will provide new dahlia varieties. Typical germination rates for these people is around 20%. The germination rates for giant variety seeds is usually lower than 20%.
Thumb of 2016-11-19/teddahlia/f2413e
Seed pod that is probably ripe enough to pick. Note that the black center is where the pollen was located and it gets very black as the seed pod ripens. One could easily feel for seeds in this pod and then pry this pod open and look at the color of the seeds. Note that the pod has lightened in color to more of a straw color. In a few more days, the sides of this pod may shrink a bit as it continues to ripen. There is no rot present on this pod and it could be left on the plant for a few more days. If you do that, be sure to mark it with some flagging tape so you can locate it again.

Thumbnail by CCvacation
Click the image for an enlarged view.

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Buying Seed
Getting seeds from other breeders:
For many years, various dahlia sellers have offered seeds for those who want to try growing seedlings. Swan Island sold them for many years. Les Connell sold them. Sea Tac dahlias sold them. I believe Corralitos sells them. We used to sell some donated seeds at our club(club members donated seeds and they were all mixed up). I am sure there are other sources. Will these seeds produce a nice flower? Yes, yes, yes. Inland Dynasty was in a seed packet sold at a dahlia society. Holllyhill Lou was in a seed packet from Sea Tac(and was named after Lou Eckoff of Sea Tac). Nick Gitts Senior gave me a cottage cheese container of seeds(that is an incredible number of seeds, probably about 5,000) that he claimed came from only giant dahlias. No giant dahlias were in the 350 seedlings that I grew from those seeds and we kept only one seedling, Hollyhill Lemon Ice. The general quality of the Swan Island seedlings was rather terrible as open centered dahlias seemed to provide most of the pollen. The seedlings were generally open center "Franken Flowers". I never planted any more of the seeds and gave most away to my enemies(actually, I explained and they still wanted them).

The best seeds that have ever been sold were from South Africa sold by the late Cyril Higgo. He grew only laciniated dahlias and in their unique dry climate, dahlias produced wonderful seeds. People who bought those seeds were blessed with excellent seedlings and many of those laciniated dahlias were introduced. Even more of the seedlings were used as seed parents and most of the laciniated dahlias of today came from that stock.

So, the big question is should I bother to collect my own seeds or should I buy seeds? I lean toward collecting your own seeds. But why not try some anyway?
And we do not ever sell our seeds and other than a few we donated to the club(and we quit doing that) , we do not share seeds. We keep the seeds for an emergency reserve. This year I had to go into my three year old seeds to get enough seeds and had we not kept them, we would not have had enough seedlings. It was poor seed germinating and seed sprouting year.

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Storing seed
Storing seed

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Sprouting the seeds
Sprouting the seeds
teddahlia wrote:How to sprout dahlia seeds using paper towels:
One roll of paper towels
Plant tags, 5 or 6 inches long
Sandwich bags, the cheap kind that only fold over, not zip lock
bowl of water

Cut one sheet of the paper towel into thirds. Fold the piece several times and dip briefly into the water
Open the folded towel and place 15-20 seeds on it and re-fold, so the damp towel will fit into the sandwich bag.
Use plant tag to list the parent(s) of the seeds and place inside bag
Place the sandwich bags in area where it is about 80 degrees
Start to remove germinated seeds in three days
All seeds should sprout in about a week.
If a seed sends the roots into the paper fibers, you can cut it out with scissors and leave the small piece of paper on it.
Place sprouted seeds into their own pot of soil with new tag.

teddahlia wrote:Larger seeds take longer to sprout, about 4 -6 days. Smaller seeds start to sprout in 3 days. Many batches of seeds are sterile, especially seeds from larger flowers. When you have a "good batch" the majority will sprout. And if you hand pollinated the seeds the results would be even more variable with the majority not sprouting. Assume that your overall germination rates will be very low and gather more seeds. Germination rates are not the goal but rather seedlings in the ground is the goal. If germination rates are low, plant more seeds. You should be aware that seeds from open center types are very plentiful and have high germination rates.

teddahlia wrote:They should all sprout within a week but some may take longer. Pretty much hopeless at 10 days.

teddahlia wrote:"how deep do you plant the seeds?" Since I germinate in paper towels, all I want to see is the slightest sprout from the seed and then I remove it and plant it about 1/4 inch under the soil. If I am unable to check the seeds for a day and one get about 1.5 inches long, I would leave about half of it above the soil.

Islander wrote:I just sow my seeds in 4" pots then move the ones that sprout so they are 4 to a pot. If any are really vigorous they can have their own 4" pot, but that way I am only dealing with the ones that want to grow, and I like repotting them. I never could see why I should fiddle with tiny sprouted seeds, or that there is any advantage to it. I would rather work with them when they are less fragile. Sort of like the difference in taking care of a preemie baby versus a full term one...

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planting out seedlings (spacing, plant height, pinching)
planting out seedlings (spacing, plant height, pinching)

“How do you space seedlings when Planting?”
Seedlings need only to be about 6 inches apart in the row and you can plant in double rows 6 inches apart.

"What spacing should 2nd year tubers grown from seed get?"
Second year seedlings should be grown as though they are named varieties and spaced as you would do for the different sizes of dahlias. AA would be spaced further apart than poms and so on.

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Defective Seeds
teddahlia wrote:Some seedling parents have more genetically defective seedlings. About 10% of one are albino that will not grow without chlorophyll. The good ones are fairly good however.

Benny101 wrote:Oddball seedling
Some seedlings are genetically defunct , and they will just push up one leaf , in this case two but never grow a stalk of any real proportion ( possibly a small nub )
Since this is in my side yard and I have more to plant I will dig it out and replace it with another seedling , have done one other like this already

Yeah this poor little guy is a mess , but one quickly realizes that they all do not make it , In life there are winners and losers ( No " participation " trophies here ) Every now and then you get one of these, I do not believe this will mature much more
Thumb of 2016-06-02/Benny101/0f9fe6

Its neighbors look like this
Thumb of 2016-06-02/Benny101/abdc24

Seeds are from the same parent , started at the same time

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Bloom analysis/culling & keeping
Both the easiest and the hardest task of breeding dahlias is the evaluation process.

When you see your "babies" you are quite proud. As with human babies, all babies look good to their mother and may well be very ugly to everyone else. If you are breeding show flowers and are a senior judge with 20 years experience, you are not easily impressed by nearly all the seedlings. If you are a show novice, way too many seedlings will look good to you. The same would apply to a cut flower person. If you have been selling cut flowers for many years, you know what you want and know what would sell.

Most beginners at breeding have not been growing dahlias all that long and should recruit some evaluation help from experienced judges and cut flower people. But having said that you are the only person that has to be impressed with your seedling. You can keep anything you want to.

"How many plants do you aim to grow of the best first year seedlings?"
4 to 6 and a pot tuber. A really good one as many as 10.

"Culling seedlings"
Knowing what to keep and what to eliminate is one of the most important aspects of dahlia breeding. As with everything that is artistic in scope, the most important thing is to keep what you like. If it is not a show flower or a flower that fits easily into the form definitions, it is still can be something that you like and that is all that counts. And Dr. Hammett believes in incremental breeding and his seedlings are generally just a step towards his final goals. So if you have one that "floats your boat" , perhaps you can use it in your breeding program and enhance the traits you admire in it.

"SECOND CHANCE- I've had many open centered ones this week with the intense heat. Do you give it a second chance with better weather?"
You imply that if the plant has a poor first flower that the breeder pulls it out immediately. Most of them get the second chance in my garden because generally I do not yank out the looser plants . I do not do so because I want to see another UGLY flower but because pulling out dahlias plants is hard work. They really have lots of roots and do not come out of the ground willingly. I may yank some out to make room for a good one and I may cut off much of the stalk. But pulling out losers is hard work and then you have to haul away the dead plant too. . Some people do rip them out right away and more power to them. -Ted
These early stinkers do not have much of a root system yet so they come out quite easy , much more difficult later on . My seedling beds are a but crowded still so clear losers are just taking up space.When they get much larger and pulling them out may disturb its neighbor , I simply cut them off at the ground and pull their tag. And storing a couple of " maybe's " is ok , sure why not .
But then reality sets in , how much storage space are you willing to part with for maybe , how much dividing , washing , storage medium Etc ? So it comes down to a time/space issue much like gravity relates to black holes. -Benny

"When to cull 2nd year seedlings?"
When a second year plant gets to blooming size, culling the plants is a major chore. 90% of your 2nd year stuff has some merit in the garden and I just leave them there and stop disbudding(like I do much disbudding anyway). Once you cull a plant, it is gone forever and you must be sure that that is what you want to do. Example: a really nice cactus in red and white bicolor went open center the second year. The flowers were not ugly but just a bit opened center. I just left it in and did not dig it at the end of the season. Many(the great majority) second year plants are not keepers but there is no hurry to obliterate them. I am always amazed how we selected such poor prospects to keep. And we are equally amazed how good some of them are. And we always pull some of very best ones from the "'also ran" second year section. We select 20-30 of the best first year seedlings and take cuttings from them. No sense having just a plant or two if it is really good one. And evaluating 4-6 plants is easier too. But that leaves 100 or so that are grown from tubers and they are planted in the "also ran" section(mixed in with the tubers from the best ones). We nearly always find some of our very best ones in the also ran garden. Two of the varieties going to trial gardens this year were from the also ran garden. So, the lesson is to give them a chance to impress you and if they have not done so in the second year, they should be culled. They do not get better the third year(but you could say you do not know as you do not keep them a third year and there may be grain of truth in that). Actually, a good percentage(less than 10%) of them get much worse the third year as they catch a disease or just break down.

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Digging Seedlings
teddahlia wrote:First year tubers are smaller. My first goal is to get at least two portions with eyes and that is by a single division of the small clump not going for any individual tubers. It the clump is bigger, I can get three divisions and bigger yet, four. A home run would be two small tubers and a division of the rest of the clump into 2, 3 or 4 sections. If a first year seedling has a clump that looks like varieties that you grow from tubers, you know it is an excellent tuber maker. But that first year dividing that large clump is not easy as the tubers are bunched together much like clumps grown from cuttings.

I have lots of room and generally plant all of the tubers from the "not best" first year seedlings. Seldom is that more than four. The best seedlings are sprouted and I take cuttings with the goal of having at least 5 or 6 of each one and few more of the very best. That means that if I keep a seedling over for a third year, I will have at least 15 to 20 tubers of it. You need that many if you plan to enter in the trial gardens the fourth year.

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Introducing seedlings/ time schedule
Introducing seedlings/ time schedule

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Hybridizer Stories
Hybridizer success/failure stories

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Misc. topics
misc. topics

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General comments for Hybridizing FAQs
-------edited 4-5-16 -

I just opened up a new FAQ, and would like to ask all of your help on getting it polished up and ready to go live.

Here's the direct link to the Hyb. Basics FAQ:

This is a good place to comment on how this Basic FAQ is shaping up, including suggestions from Active Members on what content to add here.

Please feel free to add good information in the individual questions, and one of the moderators/admin will incorporate the best comments into the original opening post. Try to keep on-topic, as one of us will have to delete non-relevant comments later.


Comments below, down to today's comment date, were directed to moderators Ted, Benny and Linda, who where chosen to help in this project for their interest and expertise in hybridizing.

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Naming seedlings & sports
teddahlia wrote:"I had never heard of either of those sports." When Encore was introduced by Swan Island they expected huge demand for tubers but the sales were underwhelming. This was in 2002. Part of it may be the name of the flower. There is an "unwritten" rule that you are supposed to leave part of the name of the original dahlia in the name of the sport.. Examples. Bronze Cornel , Vera's Elma, Pink Embrace, White Nettie, and lots of flowers named to follow the rule.
Flowers that break the rules include Aggie White that is the bronze colored sport of Bryn Terfel. It is not even white. By the way the Bryn Terfel is a Welsh opera singer and not exactly a household name here in the USA.

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Other FAQ pages that may help you:
» Help! I'm new here... What do I do?
Learn the best places to check out first on this forum!

» Dahlia Basics

This FAQ provides VERY basic info on what a dahlia is and how to tend to them, directing folks to links for more details.

» Pre-Season Questions

Quick answers on how to pre-start tubers, take cuttings, starting from seed, etc.

» Growing Season Questions

Quick answers on planting, watering, dealing with pests, topping and disbudding.

» Post-Season Questions

Quick answers on digging, dividing and storing dahlia tubers

» Hybridizing Dahlias- Advanced

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