Everything I Know About Growing Dahlias (And I'm Still Learning)
Rachel Hess**Free download at the bottom of this post.**
I gave a presentation to a group of fellow flower lovers, and when I asked how many of them had picked up their dahlias from big box stores (often imported from overseas), almost every hand in the room went up. I tried not to visibly cringe — but I'm not going to lie, I felt it in my soul.
That's when I realized there really isn't a ton of information out there for the home gardeners on where to find high-quality tubers at an affordable price, grown by flower farmers that appreciate your dollars farm more than any big box store will.
Here's the thing: dahlias grown by small farms right here in the US are out there. You just have to know where to look. (More on that at the bottom of this post — I put together a whole Local Dahlia Grower Directory resource page for exactly this.)
But first, let me share everything I covered in that presentation, because I got so many questions afterward and I want this to live somewhere people can come back to.
A little about me, so you know where this is coming from
I'm a mom of three and a third-year flower farmer. I grow using raised beds, I am perpetually covered in dirt, and I am completely, unashamedly obsessed with Pro-Cut sunflowers and now ... dahlias!
I did not expect this to happen. And yet, here we are.
I don't have a horticulture degree, my formal degree is actually in marketing. I have three years of trial and error, a lot of dead plants in my past, something that helped heal me during my postpartum days, and a genuine love for sharing what's actually worked on my farm.
Take everything I say in that spirit — this is one gardener talking to another, not a textbook. There is no one right way to growing flowers. You have to learn to play with what works for you.
Starting from Tubers
This is where most people begin, and it's a great place to start. A tuber is essentially a dahlia's root system — it stores all the energy the plant needs to get going in spring.
The most important thing nobody tells you: look for the eyes. The eye is a little growth bud near the neck of the tuber, and without one, your tuber will never produce a plant. It's exactly like a potato. No eye, no plant. Don't waste space in your beds on blind tubers.
A few things I've learned the hard way:
- Don't plant until your soil hits 60°F. For us on the border of zone 7a-7b in Southern New Jersey, that's after April 18th. Dahlias planted in cold, wet soil will rot before they ever sprout. Patience here pays off.
- Plant horizontally, about 4–6 inches deep, with the eye pointing up.
- Don't water until you see sprouts. I know it feels wrong. Do it anyway.
- Pinch at 12 inches. When your plant reaches about a foot tall, pinch out that top growing tip. I know it feels like you're hurting it. You're not. You're telling it to branch out and make more stems, which means more blooms. This is one of the highest-return things you can do all season.
Taking Cuttings — The Game Changer
This is where things get really exciting. If you want to multiply your plants without spending a fortune, cuttings are the answer.
Here's what I do: I start my tubers indoors in late February or late March in barely-moist potting mix. When the sprouts get to about 3–4 inches tall and have a set of leaves, I cut them just below a leaf node with a clean, sharp blade. I dip the cut end in rooting hormone and stick them in moist seed starting mix (my own recipe) and under grow lights. In about two weeks, they're rooted.
The magic part? The mother tuber just keeps shooting. One tuber can give you 10 to 15+ cuttings over the course of the early-season. That's one $8–12 tuber turning into a small army of plants.
This is how you can easily build up stock without spending thousands of dollars. It's also just incredibly satisfying.
Multiplying Your Investment — The Math That Makes Me Happy
Let me put some numbers to this because I think it helps:
- Year 1: You buy 1 tuber. You take cuttings — let's say 15 plants total from that one tuber.
- Fall of Year 1: Each of those plants produces a clump of 5–10 tubers when you dig them.
- Year 2: You now have potentially 75–150 tubers from that one original purchase.
That's not a typo. One tuber, properly propagated, can become over a hundred plants in two seasons.
Dividing clumps is the other piece of this. When you dig in the fall, you'll pull up a big clump of tubers all attached to the original crown. You need to carefully divide these — one tuber at a time — making sure each division has a neck and at least one eye. A sharp knife, good light, and patience. And for the love of everything, label every single one. You will not remember. I promise you won't.
The alternative to this is leaving your tubers in the ground, heavily mulching them with straw after chopping the stalks down, and tarp everything for the winter. Either way it's a gamble, storing vs. tarping. It's ultimately up to personal preference.
How I Grow Them on the Farm
I grow in raised beds, and I space my dahlias 9 to 12 inches apart in an offset pattern — also called a diamond pattern. Instead of rows lined up straight across, each plant in the second row sits in the gap between two plants in the first row.
This does two things: it lets me fit more plants in the same space, and it keeps air moving through the bed, which is one of the best defenses against powdery mildew. I can also quickly strip any foliage that's needed to be disposed of this way to help increase even more airflow.
A few other pro tips:
- Drip irrigation. This is the most consistent way to water your dahlias, without over-watering. Also, wet leaves are an invitation for problems. That being said, I started out using sprinklers overhead (because, hello? rain) and the dahlias were just fine.
- Stakes or flower netting at planting time, not after the plant falls over at 4 feet tall. (Ask me how I learned this.) You can use 2x2 wooden stakes or t-posts for your corners and use plastic or twine to help corral them.
- Rich, well-draining soil amended with compost. Raised beds give me control over this that in-ground planting doesn't. I always use a mushroom/topsoil compost blend that does just the trick, delivered about 3-5 yards at a time.
- Deadhead constantly. The more you cut, the more they bloom. This is true in the garden and it's true on the farm. Never let a spent bloom just sit there.
Growing from Seed — My Favorite Kind of Surprise
Okay, this is my thing. I love growing dahlias from seed, and I think everyone should try it at least once.
Here's why: when you grow from seed, you have absolutely no idea what you're going to get. The color, the form, the size — it's all a mystery until that first bloom opens. And because dahlias are open-pollinated and cross-pollinate freely, no two seed-grown dahlias are genetically identical. Every single plant is an original.
I find this intoxicating. You might end up with something that looks like nothing you've ever seen in a catalog. You might grow a variety that doesn't exist anywhere else in the world. You might even find something worth naming and propagating.
It's also the most budget-friendly way to grow. A packet of mixed dahlia seeds for a few dollars can give you 25 or more plants. Compare that to buying tubers one at a time.
Practically speaking: start seeds indoors 4–6 weeks before your last frost date. Transplant outside after hardening them off. They'll bloom later in the season than tubers, but they'll bloom.
My kids also love this part. There's something about checking on tiny seedlings every morning that never gets old, no matter how old you are.
Season-Long Care: The Short Version
- Pinch at 12". I said it once. I'll say it again.
- Water deeply but infrequently. Dahlias don't like wet feet. Raised beds and drip irrigation are your friends.
- Fertilize low-nitrogen once established. High phosphorus and potassium support bigger blooms. Don't over-feed early or you'll get beautiful plants with no flowers.
- Watch for earwigs, slugs, and thrips. Check your blooms every single day during peak season. Treat organically when you can.
- End of season: After the first frost blackens the foliage, cut back to a few inches, dig the clumps, cure them for about a week in a cool dry spot, then store at 40–50°F in barely damp medium (peat, vermiculite, or wood shavings all work).
- Label. Everything. Always. I cannot stress this enough. Future-you will be so grateful.
The Free Download
The presentation I gave at the talk covers all of this with visuals, a planting diagram, and a breakdown of different dahlia forms (dinner plate, ball, pompon, cactus, waterlily, anemone). I'm sharing it here for free because information should be free, and more people should be growing dahlias.
[Download the presentation here → Growing Dahlias: Seeds, Tubers Cuttings & Blooms]
Please Don't Buy from Big Box Stores or Imported Tuber Clumps (Or at Least, Try Not To)
I say this with love. I understand why people do it — it's convenient, the selection is huge, and the marketing is beautiful. But when you buy from a large overseas importer, the money leaves your community entirely. The tubers travel thousands of miles. And you're missing out on some genuinely extraordinary small farms doing incredible work right here in the US.
I've put together a Dahlia Grower Directory on my resource page — a searchable list of small dahlia farms across the country where you can buy directly. It's a living list and I'll keep adding to it.
Support a small farm.
Ask them questions.
Buy weird varieties you've never heard of. That's the good stuff.
Questions? Drop them in the comments or send me a message. I love talking dahlias.
— Rachel, Bits & Blooms Flower Farm
