Delphiniums are one of my favourite perennials to grow. I love their beautiful blue hues and they’re always a welcome sight sometime in early July. In bouquets, they can be a bit tricky to use, so I often prefer to use the side shoots. My favourite colour is the light blue with the white bee (Side note: Did you know that the little inner part of the flower is called the bee?!), but they’re equally dreamy in shades of white, pink, and light purple.
I’ve recently learned about a couple of new varieties that have more of a branching habit for an airier look–Jenny’s Pink Pearl (pink) and Cliveden Beauty (light sky blue)–and I hope I might get just a few stems this year so that I can see what they look like in real life!
Starting delphinium seeds can be a bit tricky, but with the right steps, you can grow these beautiful flowers successfully. Here’s my quick step-by-step guide to help get you started!
Step-by-Step Guide for Seed Starting Delphiniums
1. Start Early for Bigger Plants
I recommend starting delphinium seeds indoors 12-16 weeks before your last frost date. You could start as close as 8 weeks, but I would not recommend waiting for the 6-week mark. In colder zones like mine, delphiniums are best started indoors early because they require a longer growing season. Starting them indoors helps ensure that they have enough time to grow and flower.
2. Cold Stratification is Preferable
Delphinium seeds require a period of cold to break dormancy. To mimic the natural winter conditions, you can cold-stratify the seeds before planting them. To do this, simply place the seeds in a moist paper towel, seal them in a plastic bag, then store the bag in the fridge for about 2-3 weeks.
Related: 10 Perennials That Require Cold Stratification
3. Choose the Right Soil
As long as you don’t have super poor soil, your delphinium seedlings will be fine. You don’t have to be precious about it. That said, in my experience, they’ve thrived more easily in clay/loam soil than in the sandy soil at this acreage. At my old house, they were a lot easier to get established!
4. Sow the Seeds
Fill your seed trays with seed-starting mix (or use soil blocks), and sprinkle your delphinium seeds lightly on the surface of the soil. If I cover them with anything, it’s vermiculite (which, apparently, is made in the U.S.—so now I have to stock up!). Gently pressing the seeds into the soil helps ensure good seed-to-soil contact.
5. Provide Warmth & Light
Keep your delphinium starts under grow lights and ensure the seedlings get around 16 hours of light per day. Ensure your grow lights stay a few inches above the seedlings, adjusting as they grow.
Related: The Best Grow Lights for Seedlings (From Budget to Bougie)
6. Send Outdoors Early (optional)
If you’re short on space under your grow lights, you can plant delphiniums out early. They should be fine even if you move them outside in early May instead of waiting until the third week.
Don’t Expect Blooms in the First Season
With most perennials, it takes about three years before you get substantial blooms and five years for the plant to fully mature, which I really learned at our last house. Delphiniums are also easy to divide, so if your plant outgrows its space, you can simply divide it and plant the extras elsewhere.
It’s really that simple! There’s not much you have to do. I used soil blocks in the pictures in this post, and though I used my wool pellets incorrectly this time, I will be writing a post about the proper use of wool pellets soon!
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Karen L