Growing Dahlias From Seed…
There is nothing better in July and August than visiting the Dahlia patch and seeing what is blooming from seeds that you planted back in March/April (or possibly earlier if you’ve got access to a heat mat).
Dahlias have much more genetic variability than other plants, meaning that if you plant a seed it’s not going to look like the parent. In my experience many of the seedlings tend to have some traits of the parents but the variety across the sibling seedlings is incredible.
What you end up with is also heavily influenced by how the dahlias were pollinated. If you leave it to the bees then you are going to get some lovely flowers but they will mostly singles and open-centred varieties (unless you are strict about not having any singles and open-centred varieties elsewhere in the vicinity).
If you want more influence over the results then you can also branch out into hybridising the dahlias yourself. There are a lot of videos on YouTube etc showing how to do this but it is a lot more work.
The seeds we sell are mostly open-pollinated varieties but often I will list one of the seed parents so you can see if they show any parental traits.
My advice for good plants is to start them off in Feb-March (with artificial heat and lights) or April (under cover). Germination should happen between 18-21°c but can take a couple of weeks (sometimes longer). The seedlings must be protected from frost and slugs (slugs and snails love dahlias). They can be planted out after the risk of frost has gone. I have never had good results from direct sowing so best to start them in individual pots/plugs.
Once they start to bloom in July/August time you can pat yourself on the back and decide whether the flower is good enough to keep. If you don’t like it pull it up and throw it on the compost. If you do then you can save the tuber for next year and regrow. Don’t make the decision from the first bloom - often the first bloom on each dahlia isn’t the best so leave it to flower for a few weeks before you decide.