Growing your own dahlias from seeds can save hundreds of dollars if you want a large flower garden. Getting started is easy, and this article will walk you through each step!
It's not quite March yet, but already started a shelf full of seedlings, in front of my big south-facing window. The last year has been a long one, and I need green and growing things in my life.
I decided to let myself get started a little early this year, and I'm not sorry. Not yet, anyway!
My kids like to call small plants, "greenlings", and I think it's sweet. Of all the darling greenlings on my windowsill, the ones that put the biggest smiles in my heart are the Dahlia babies.
They're so robust and joyful. Each one looks a bit different. They're full of promise and the hope of summertime. If you've never tried it, starting dahlias from seed is a fun project, and a great one to do with kids!
Here are the really easy steps for starting Dahlia seedlings indoors:
1. Choose a good seed-starting mixture
For the best results, you'll want to choose a good, light soil that's meant for seed starting. I especially love this seed starter mix from Coast of Maine.
I've also had good results with the Jiffy Organic Seed Starter, which tends to be available at both Home Depot and Walmart stores, usually for somewhere between $4-6 a bag.
Choosing a good light starter mix is beneficial, because it helps to prevent "damping off". It also encourages those little seedlings to establish better root systems than you might get from working with heavier garden soil.
Cold house? No worries.
Here's how to start seedlings in a cold house
2. Fill pots or seedling flats with soil
The best way to do this, is to get your seed starter mix lightly damp. It really helps with correctly filling the pot or seedling flat.
You don't want it soaking wet, just nicely damp to the touch. When you grab a handful and squeeze, the soil should clump together for a moment before falling apart.
Fill the cavities of the seedling tray with soil, then lightly tap the tray on a counter to make sure the soil is nicely settled. Top it up if you need to. You want the level of the soil to be just below the plastic ridges that run between each cell.
Once the seedling tray or pot is filled, you'll want to set it in something that can catch water, like a drip-proof tray. (Unless you're starting in a greenhouse, where wet floors don't matter!)
Dahlia babies go through quite a bit of water, and you want to make it easy to keep them well-hydrated.
3. Plant the dahlia seeds
Oh, this is the fun part! Dahlia seeds are dried little brown whisps of things, that often seem so flat it's hard to believe there's any life in there. Don't worry about the variation in seed shape.
So far, in my experience, there's been no difference in germination rate based on whether a dahlia seed is plump and big, or flat and shred-like.
There will be a thinner, pointier end, and a flatter, wider top. Poke the long seeds vertically into the soil with the pointy end down. You want the flat top to be just below the surface of the soil.
Dahlias are robust little plants that want space to grow, so unless you have reason to believe your seeds are old or have a particularly low germination rate, just tuck one seed into each cell.
If you've already dampened the soil when filling the trays, there's no need to water. If you planted them into dry soil, water just enough to dampen the soil. You want them to have moisture, but not sit wet.
4. Wait for seeds to germinate
You don't have to wait long. While there tends to be some variation from one variety of dahlias to another, most of my dahlia seeds this year have sprouted in just 5 days.
A couple took as long as 10 days, but really almost all of them were poking up from the soil in a week or less.
Once the seedlings are up, continue to keep them watered. I find these little cuties use more water than many of my other seedlings, so do keep an eye on them. You don't want them sitting wet, but don't let them dry out for long either.
5. Harden off, before planting
As with most seedlings, Dahlias benefit from "hardening off" before they get planted outside. You want them slowly growing acclimated to direct sunlight and wind, rather than getting shocked by going from indoor life to being outdoors all day and night.
Harden your seedlings off by setting your them outside for just an hour or two, then increase their time outside by a couple of hours each day, until they're fully acclimated.
This will help them avoid sun scald, and make a stronger, more graceful transition to the garden.
Once you've followed these steps, you'll have strong young Dahlia seedlings, ready for the flower garden.
Plant outside well after any risk of frost, and follow the same growing methods you would for tuber-grown Dahlias.
By the way, if you love Dahlias, and don't already have Floret Farm's Discovering Dahlias book, I cannot recommend this book enough.
It's an absolute MUST-HAVE, in my opinion!
Some frequently asked questions about starting Dahlias from seed:
Are seeds the only way to start new Dahlia plants?
Nope! You can also start new Dahlia plants by dividing the tuber clumps between growing seasons. Each tuber with an "eye" will start a new Dahlia plant of the same variety as the parent plant.
You can also start new Dahlia plants by taking cuttings from a parent plant, and rooting them!
Will seeds produce the same variety of Dahlia as the flower they came from?
No. Unlike with a tuber, where the "child" plant will be genetically identical to the parent, Dahlia seeds will produce a new, genetically distinct plant.
This new plant will likely have have traits inherited from both the plant that produced the flower your seed came from, and the plant who's flower produced the pollen that fertilized it.
With Dahlia seeds you never know what you're going to get, and that's part of the fun of it!
Why start Dahlias from seed?
If it's easy to reproduce Dahlias by dividing the tubers, why bother starting from seed? There are a few compelling reasons!
1. Cost. It's SO MUCH CHEAPER to start lots of Dahlias from seed, than buying tubers or plants! You can start a whole garden full of Dahlias for less than the cost of a few high-quality tubers.
(The downside of course, is you never know what you're going to get! That whole garden may have just one or two plants with traits that you just love. With tubers you know exactly what you're getting.)
2. Plant Breeding. Developing new plant varieties is addictive! I have gone down this road with tomatoes, and it really gets you hooked. By intentionally crossing certain varieties, and growing out the resulting seeds, you can work toward creating new varieties that have the color, form, and traits that you're looking for.
3. Fun. Dahlias are easy to start from seed, and it's a fun way to add a lot of color to your yard without much cost. Starting Dahlias from seed is a really great springtime project to do with kids!
What size seedling tray should I use for starting Dahlias?
Great question! 10"x20" seedling trays come in different sizes--some with with fewer, larger cells, and others with many, smaller cells. They're generally referred to by the number of cells in the tray.
For starting Dahlias, I've seen everything from 128, to 72, to 48 trays suggested. For me, I'm finding the 72-cell tray to be a great size that allows me to start a lot seedlings in a smaller space, while still allowing room for each seedling to grow a good root system.
That said, I'm just a small-time gardener, and not a professional plant breeder.
If I were growing out thousands of seedlings for a breeding project, I can absolutely see how the 128 cell trays would be the way to go!
How early should Dahlia seedling be started indoors?
The general recommendation is 4-6 weeks before the last frost date in your area. For where I live in Maine, that means around April 1.
Dear friend, I tell you this with love. Do as I say, not as I do.
We all know I have Dahlia seedlings sitting in my window sill right this very minute.
The truth is, once they get started, Dahlia seedlings do grow quickly. Erin Benzakein, author of the Discovering Dahlias book, recommends not starting them too much earlier than 4-6 weeks, since larger seedlings don't transition to the garden quite as gracefully.
This is the way.
Growing Dahlias from seed is really a joy, and I do hope this post helps get you started!
I'm still new to Dahlias myself, but if you have questions I have answered, drop them in comments below! If I don't know the answer, I'll try to sleuth it out for you!
Happy growing!
Anna Chesley is a freelance writer living a homestead lifestyle, with a special love for family travel, old books, vintage skills, and seaside living. In addition to founding Salt In My Coffee, she runs the website, New England Family Life, as well as The 1800's Housewife, a website devoted to re-creating authentic 1800's recipes.
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