Updated: Dec 2
Dahlias can be propagated in one of 3 ways, from splitting tubers, from cuttings and from seeds.
Propagation from tubers and cuttings will clone the parent, so all the new plants will be identical to the parent. Propagation from seed allows new variations to occur and that's when the magic really happens! Dahlias are octoploids which means that they have eight sets of chromosomes rather than two.
This means there is much more variation with literally millions of different possible combinations so each seed is almost totally unique. Even if gathered from the same seed head each seed will be genetically different and produce different characteristics.
There are many breeders across the world who plant thousands of seeds each year and hope to produce something even more beautiful than the parents however due to dominant and recessive traits it's not that easy. Many of the traits we think are the most beautiful are unfortunately recessive so will not occur very often, and there are so many traits that getting the stars to align is a bit tricky too.
There are a few ways in which you can start to breed Dahlias
Open Pollination - Simply let nature do all the work. This method is good for dahlias with open centres. Simply put it's easy for an insect to cross pollinate as they have easy access to the centre of the bloom. They are most likely to be carrying pollen from another open centred bloom so its more likely that these seeds will produce open centred blooms. In addition open centres are a dominant trait. This does work for double forms of Dahlias but you may need to strip some of the petals to make it easier for the bees to gain access.
Plant Culling - Here you can still let nature do all of the work but by removing all flowers on plants where you do not want cross pollination you can eliminate the genetics you do not want to replicate. So by removing certain colours or forms you can narrow down your end result with more favourable odds.
Hand Pollination - by combining the genetics from two favourable plants you are likely to get the most success, (but is not guaranteed). Good seed and pollen parents will produce the most viable seeds so it pays to choose wisely and if you can find good seed and pollen parents then these can be used repeatedly.
Once pollinated it will take around 6-8 weeks for the seeds to mature. They should be harvested when they are elongated and dark brown or black. Green seeds or seeds which are not elongated will not have been pollinated and will never germinate. Separate the seeds from the chaff and dry inside for a couple of days before storing in a labelled brown envelope. From open pollinated seeds you should be able to get seeds heads full of ripe seeds.( 50+) but from a hand pollinated seed only a handful - the bees do a much better job than we can ever do!
So if you would like to try your hand at Dahlia breeding then look out for my next blog all about the dominant and recessive traits you can look out for.
In the mean time if you are lifting and storing Dahlias for the winter then check out our blog post Lifting & Storing Dahlias