Starting dahlia seeds

calico20hill · 2023-03-05T22:07:16+00:00

I am excited to see plants growing form Rock Run Ashley seeds I collected last year. I don't think I have tried seedlings from it before. I started quite...

Teddahlia

Seed starting is combination of disappointments and success for us. You want the special seeds to sprout and you celebrate when they do. You have enough seeds to plant several acres if they all sprout. ☺

Bessie

Teddahlia I expect 5% sprouting at the most. I'll try to keep track. Most of the seeds seem like they are blanks.

Bessie

I found an interesting 2025 research study on the optimum temperature to germinate Dahlia seeds. Seems that 20 degrees centigrade ( 68 degrees fahrenheit) is optimum. I'm sure that's what many experienced growers would have told me! So, my seeds are now at room temp in my house, where the thermometer sits at 68 degrees fahrenheit.
The study found Dahlia (Dahlia variabilis) seed germination results:

Twenty-one days after sowing, the maximum seed germination frequencies (70.0%) were observed at 20°C, regardless of illumination conditions, followed by 61.0% at 25°C (illumination) and 51.8% under 25/20°C, respectively. Seeds incubated at 25°C (darkness) germinated with a frequency of 33.3%, while no germination occurred at 30°C, irrespective of illumination conditions.

Teddahlia

We have been sprouting dahlia seeds since about 1995 or before. By now, we should know what we are doing but we always feel that we are not vey good at it and could do better but just about everything we try is seldom much better.

Bessie

Question: What's your philosophy on "growing on" dahlia seedlings that aren't super star growers? I'm thinking of the ones that don't have shiny pretty leaves, and aren't stocky and solid. Also, do you keep seedlings that are very nice plants, but are petite and slow growers?
Backstory: I started seeds on Jan 27th and more on February 2nd. I've got lots and lots of seedlings, I think at least 450! Some of the seedlings got cold damp feet, so they exhibited nutrient deficiency which seemed to mostly be lack of magnesium. I fixed that problem by setting up heat mats, which I should have set up to start with! I also did a foliar spray of magnesium sulfate.
Some of the nicest fast growing seedlings have been potted up two weeks ago and are happy outside. The other seedlings are now all outside in full sun, still in their 3 ounce paper "Dixie cups". It's projected to be 80 degrees F. this weekend.
Side note: I figured out what "disease" killed 90% of last year's 2025 seedlings.... I'm convinced (after careful analysis) it was the heat mats I hastily put down right before I went on a 6 day vacation. I fried the roots!

SteveM

Bessie Question: What's your philosophy on "growing on" dahlia seedlings that aren't super star growers?

If I had lots of room I would grow all of them, otherwise just the strongest. Occasionally a weak seedling will get a second wind and grow normally but usually they are hidden by their more robust neighbors.

Teddahlia

I babied the stragglers along for many years. Then I planted them together in the last row. I noticed that we almost never kept any of those seedlings. So, I toss the poor performers nowadays.

When I say heat mats are plant killers, no one believes me. I just found my 8 foot expensive heat mat rolled up in the basement where it has been for about 5 years now.

Bessie

Teddahlia now that you mention the "last row", I did the same thing two years ago. I put the smaller weaker plants in one particular area. They were not impressive, as I remember.

MissyWeitzel

6 of my Kenora Wildfire seeds sprouted then failed right away. It's not likely the environment as many other seeds are in the exact same spot and are germinating and growing normally. I've never seen this happen!

SteveM

MissyWeitzel 6 of my Kenora Wildfire seeds sprouted then failed right away

That's interesting, was the pollen parent the same on all seeds (hand cross)?

Teddahlia

Growing seedlings is frustrating. Some crosses give you seedlings with fatal flaws and they will not grow.

MissyWeitzel

SteveM nope, open pollinated.

Teddahlia

We grew Wildfire only once years ago and did not try to collect seeds. Larger dahlias make poorer seeds. When breeders talk privately, one of the common subjects is how to get seeds(and of course seedlings) from giant dahlias. I will say publicly that everyone has problems with giant seeds or the lack there of. AC Dahlias has had the most recent successes and he said in a pod cast that he likes to grow the the potential pod parents in crowded conditions. I bet he does a lot more than that.

Bessie

Today,(zone 9b) I'm planting in the ground some of the seedlings started on Jan 27th and February 2nd.
I decided to plant 3 seedlings from the same seed parent per hole. My plan is to have aggressive culling and taking cuttings from the nicest seedlings. The holes are on drip line 12" apart.
Several seed parent varieties made beautiful seedlings. Hollyhill Serenity and Hollyhill Creamy are in this picture, along with a first and a second year seedling parents.
Top view:

View with some seedlings in the background:

The weather in March has been more like April, with a high of 78 F. expected today.
Notable beautiful seedlings this year include Apricot Desire, Hollyhill Serenity, Hollyhill Wedding Day, Molly Raven, Sweet Nathalie, Hollyhill Black Beauty, Hollyhill Creamy. Seedlings that have Hollyhill Daydream or Bahama Mama as it's maternal grandparent also look nice(this is seed from second year "keepers").

SteveM

Bessie Beautiful! You have some great seed parents and I expect you will get many, many keepers.

Bessie

SteveM I can hope I'll have some nice ones! The evaluation will be much different than my first year growing seedlings in 2023. I know so much more now about quality and what I'm looking for.

Teddahlia

We hope our "sort of looks like Molly Raven" seedling does well.

Bessie

Bessie warm weather is record breaking here in Northern California. I finished planting just under 150 seedlings in this repurposed vegetable bed. Almost all of the seedlings are planted 3 to a hole in wire baskets purchased from Amazon.

The baskets are called 1 gallon size, however the inner dimensions are 9x10" rectangular when laying flat. I might learn to regret using these, as well as planting three to a basket. I don't see a way the gopher will eat through these, since they're a lightweight chain weave. The gophers may just come over the top as they have been known to do! I plan to add some carrots as indicator plants to the outside edges of the bed, since the gophers will hopefully eat the carrots first and I'll then know I've got a problem.

Teddahlia

Evaluating seedlings sounds like the easiest part of growing seedlings. No one, no matter how experienced will select all of the best ones and will instead fall in love with several flowers that only you appreciate. The stories of beginners "hitting a home run" on their first several batches of seedlings and not knowing it are numerous. They can have a happy ending when the seedling is given to some one else who "rescues' it from the unappreciative breeder and the variety becomes "famous".
Remember the all time classic story of the top selling dahlia of it's era: Chilson's Pride. I heard this story directly from Marge Gitts who was there.

calico20hill

I am starting very few seeds this year...because I started so many last year and got so many nice tubers that I stored, and now I need to evaluate those more and eliminate all but the very best. Since my garden is not expandable without thousands of dollars of work, I need to get the number of keepers way down, which of course means growing them again to make decisions about who stays. On the other hand, I Am really excited about seeing some of them again!

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