This winter, I compared 4 different types of delphinium in a sort of trial (unsponsored and not super scientific) to try and figure them out a bit better. I had crummy results and germination last year, so I wanted to find out how I could do them better.
The four types of dephinium seeds were: Belladonna Mix (Johnny's Selected Seeds), Black Knight (Outside Pride), Summer Skies (Outside Pride), Astolot (Outside Pride).
I tried them three ways:
First Test: "The Over-Heater"
I wrapped separate varieties of delphinium seeds in damp paper towels and plastic wrap. I put them on a heat map. The next day (gulp) I found that the heat mat sensor had not been properly placed. The mat was hot-- maybe 95 degrees hot. I turned the heat down to 70F, where I planned for it to be set, and let the seeds sit several more days. When I went to plant them, I noticed that there was a spindly mold growing across the seeds. But hey-- might as well keep going and see what happens, right?! Then I planted them in a 128-cell tray with damp germination mix to see what would happen. I planted 32 cells for each variety and 3-4 seeds per cell. The tray was placed under grow lights in our home office which is about 65-70 degrees.
The top performing variety was clearly Belladonna Mix. The next was Astolot. Belladonna sprouted faster and yielded a few more seedlings. Black Knight and Summer Skies gave me nothing.
Second Test: "Wrapped and Warmed"
I tried the damp paper towel method again. This time, instead of using the heat mat, I put them on top of one of the flourescent light fixtures that we use as a grow lights. It doesn't get more than a little bit warmer than room temperature. This time, I saw even more spindly web mold. I planted the seeds out in a 128-cell tray again. I pressed the seeds gently into the mix. Again, the cell tray went on to a shelf under grow lights in the home office. The mold disappeared, and the Belladonna series performed even better-- with almost 100% germination. Astolot followed with less germination. I didn't see any Black Knight or Summer Skies.
Third Test: "Cool and Dark"
This time I didn't use the damp paper towel treatment at all. Hoping to avoid the weird mold I sowed the seeds 3-4 per cell directly into a 128-cell tray with moist germination mix. I pressed the seeds gently into the mix. To further mix things up, I put the tray down in the cellar (50F) with the Larkspur trays (they are related anyways!) to see if maybe these delphinium just need some darkness to germinate. Other than checking to make sure the surface stayed damp, I tried to forget about them for 10 days. After nearly 2 weeks, there was no germination. I'll wait a bit longer and see what happens. I'll update this post if anything seems worth sharing.
So, there you have it. Things I'll want to test next time: different seed sources, different chilling periods for the seeds, using some of my own saved seeds. For now, I know that I'm best off buying the Belladonna variety - as it readily accepts the most torture and still sprouts!
If you have some delphinium suggestions for me, please share! I'd love to get them nailed down better. I hope my experience this winter points others down a clearer path, too. One thing that I learned last year is that delphinium really need light soil mix. Don't allow the seedlings to become water-logged. Let them to dry out between waterings. My seedlings also seem to be performing much better this year in our cool basement under grow lights, in comparison to the glass house last year. The first round of Belladonna and Astolot are filling the 4-inch pots I bumped the up to. They are good to plant out, but I'll wait until the next few really cold nights have passed before I stick them under the low tunnel that is sheltering the delphinium.