Breeding Dahlias
                                                                                                  Presentation to PDS 07-10-18
                                                                                                       by Ted J. Kennedy

Introduction:
All the varieties you grow in your garden were once grown from a seed.  Dahlia flowers do make seeds and part of this presentation is on how to harvest
seeds that can produce good flowers. Lots of people who grew dahlias over the years devoted a small area in their garden for a  few seedlings. Some of the
most famous and best dahlias were bred in small gardens. Some people bought seeds from growers and wonderful varieties were the result. Inland Dynasty
was a seedling from seeds harvested by Dick Ambrose of Camano Dahlias and they were donated to his club to be sold. The seeds were bought by the
Anselmos and were grown in a small garden in Spokane and one of them went on to be one of the most famous giant dahlias.  Dick Ambrose said it was the
one that got away.

Harvesting seeds: The most obvious practice is that you must not deadhead your flowers to get rid of spent blooms. That sounds awfully basic but many
people have this habit built into their sub conscious minds. I have had people visit our gardens and start to deadhead plants
“as a favor” to me not even thinking that those spent flowers were being saved to make seeds.
There is a time line for seed production and as an example for BB sized dahlias it goes like this:
Step(1): the yellow pollen center appears
Step(2) about 2 days later the pollen center sends up it’s  pollen stamens with it’s anthers that produce and distribute the pollen. Note that the male parts of
the flower appear first and the flower stops producing pollen when the female structures appear in the same area.
Step (3) the pistils appear and they resemble tiny flowers. They are receptive for pollen for a few hours. There are several hundred pistils that form over the
course of a few days.
Step (4) after the pistils stop appearing the flower goes through the ripening process that lasts about 2 weeks. During this time the seeds inside the pod
change color. They start out as white, turn green then tan or brown and finally either a dark brown or usually black.  They can be inspected by peeking into
the pod and looking at the color.
Step (5) the seed pods are harvested either at the stage when the seeds are ripe as above or can be left on the bush to further ripen as the pod itself turns
color.  It goes from green to a light brownish green and eventually turns brown. In Oregon in late September and early October when most of us gather
seeds, it is a very risky practice to leave the ripening seed pods on the plant longer than necessary. It is exceedingly common for the pods to rot, killing all of
the seeds.  Harvesting when the seeds are ripe is better than leaving the pod on the bush to further ripen. And the next step is shucking(removing the
seeds) from the pod. We do it within a few days of harvesting and do not want the seed pod to dry out. Dry seed pods have what is called chaff and
shucking dried seed pods is an overly messy process that we avoid.
Seeds from fully double dahlias have a gemination rate of about 20% but that is an average and it varies from 0%(probably about 33% of batches of seeds
will not sprout) to as high as about 75%. For us a batch of seeds that sprouts at about a 40% rate is a home run. Seeds should be dried completely and
labeled and then stored in small envelopes in the freezer(protected from frost perhaps in a quart glass jar). They will last for over 10 years if you store them
in the freezer whereas seeds stored at room temps sprout well for only about 2 years and very few sprout when older than3 years.


Breeding Dahlias: If you have taken a biology class and studied Mendel and his pea seeds you have some idea about how genetics works. You know that
there are traits that are dominant and traits that are recessive and that there are homozygous and heterozygous organisms.  You are aware how the
breeding is done to isolate good traits and to eliminate negative traits.  Once a good trait has been isolated, all of the seedlings will have the good trait and
the breeder works on isolating other good traits.  

Mendel did not know how to breed dahlias. His peas were diploid meaning that they have two sets of chromosomes. Dahlia are octaploid meaning that there
are 4 sets of 2  for a total of 8 chromosomes.  Plants can have more chromosomes and there are lots of them that are octaploid including strawberries,
pansies and sugar cane.  When you increase the number of chromosomes to 8  you can have 4 times as many genes available for each trait. So for
example blue eyes in people(people are diploid) is a recessive trait. If you have both of the blue eye genes your eyes are blue. If you have only one gene
for blue and one for brown your eyes are brown. In dahlias the flower could have any combination blue and brown genes like 5 blue and 3 brown. But when
you have 8 spots you could have room for another eye color like green eyes. So you could have 5 blue , 2 green and 1 brown. So, what color would the
dahlia eyes be?

Let’s jump ahead to how you actually breed dahlias knowing that they are octaploid. Strawberry breeders know that to breed octaploid plants you need to
get the best seeds possible and grow lots of seedlings.         They say 10,000 strawberry seedlings are grown to get one new variety.        Note: strawberry
breeders must taste their creations to evaluate them.  Most of them do not taste good.

How do get the best seeds possible?  In breeding you control the pollination to make sure the flowers are pollinated by another flower of your selection.
The most accurate way is to hand cross the mother plant and to take precautions to ensure only your hand cross is the one that makes the seed..  This
method is extremely time intensive.

The next best method to control pollination is to plant flower varieties near each other and hope that the bees will cross the plants in that area.  The Boleys
have a 5 acre field of grass. In that field, they plant small dahlia gardens of flowers they want to cross. The gardens are at least 50 feet apart. The late Mike
Iler used this method too.

Kenora dahlias were bred by Gordon Leroux. I met him once and asked him this very question. He did two things to get his flowers pollinated correctly. First
he removed all the “bad” flowers before they made any pollen.  Then he harvested bouquets of “good” flowers and placed them near the flowers he wanted
to be pollinated by the bees.

How do you select the varieties that you want to cross? It sounds incredibly stupid but one of the most important criteria of all is whether a variety has
the ability to make seeds. Most dahlias(at least the ones you want breed) do not make seeds.  So you need to know that the variety makes some seeds and
if you are just starting out you need to ask some breeders for a list of seed makers. It is less important that you know another variety makes some pollen.
Most do make pollen but again many do not. Now that you know a variety makes some seeds, you can select some flowers  to cross with it. Dahlias are bred
for form, size and color. Most breeders know that form is quickly lost if you cross two different forms together. So they cross flowers of the same form and
worry less about size or color.

Since you cannot use diploid breeding techniques, especially the process of creating homozygous seedlings, you need to employ a different strategy.  In
ancient times plant breeding was incremental and seeds were collected from the best examples until over time the variety was improved.  That is still the
strategy for breeding dahlias. If you cross plants that have similar form, the seedlings will tend to retain that form.                 

Dr. Keith Hammett of New Zealand uses a slightly different breeding strategy. He uses a “five” year plan and uses isolation beds to produce seeds from
selected varieties. He selects the best seedlings from that first cross and saves seeds from them and no longer uses the original selections to produce
seed. He does this for about 5 years until he has incrementally improved the stock to meet his goals.  He does not retain seedlings that were used on the
way to his goal.

Color in dahlias is a very complex but interesting subject. There are so many colors in dahlias because two sets of color pigments were combined when the
first dahlias were created from the two species of dahlias that crossed . Since dahlias are octapoid, having two sets of slightly different color genes means
that the colors will vary greatly in many ways. In the future, I want to do a lecture on color in dahlias as it is a fascinating subject.


Goals: Note I have not mentioned the word “ Goals” and all plant breeders, even casual ones have goals. Dr. Hammett has very specific goals and
successful breeders and casual breeders all have goals. You will do much better as a breeder if you decide to breed a specific but well defined dahlia. Your
goal may as simple as I want to breed a nice pretty cut flower but as simple as that sounds you are committing to having a flower that is pretty, that has a
closed center, nice stems and is vigorous and makes some tubers that keep well.  If you add a specific color or form to that goal it gets even more
complicated.

Evaluation:  My last comment about breeding dahlias is probably the most important but probably overlooked by many.  It is the evaluation of the seedlings.
It sounds so easy: you are tasked with cruising through your seedling garden and selecting the good ones to grow again. Who would not recognize a really
nice flower in the seedlings?  Mingus Toni and Rivers Novelty and probably many other very successful dahlias were culled by the breeder and “rescued” by
a visitor to the breeder’s garden who really liked the flower. You are a very biased evaluator of dahlia flowers and have likes and dislikes.  Let others see
the flowers and get another opinion. Here at our club, several back yard breeders have brought vases of seedlings to our meetings and asked for input.
The breeder pulls out his favorite flower from the vase and I try to be polite as I point out it’s problems yet in that same vase is a really nice flower.
Hollyhill introductions and
unreleased seedlings, click to
enlarge