Growing dahlias from seed is a fun, and exciting, process!

Unlike dahlias grown from tubers, dahlias from seed will not be true to the parent plant that the seed was collected from. They will be genetically similar but a complete surprise! Due to open pollination, dahlias grown from seed will be a brand new bloom!

With notoriously low germination rates, germinating dahlia seeds can be on the trickier side. However, there are lots of ways to go about it and with a few tips, you could be growing brand new beautiful dahlia blooms in your garden this summer.

Scroll down to for a deep dive into methods to achieve higher dahlia germination rates and growing tips!

Jump to:
The Basic Information on Dahlia Seeds
Paper Towel Method of Germination
How Long Do Dahlia Seeds Take to Germinate?
Transplanting Sprouted Dahlia Seeds into Potting Soil
How Soon Do Dahlia Seedlings Emerge after Planting?
Transplanting Your Dahlias Out into the Garden and Growing On
What Makes A Good Cut Flower Dahlia?
SCF’s Favorite Seed Starting and Growing Supplies

The basics of dahlia germinating seeds:

• Start your seeds 4-6 weeks before your average last frost
• Seeds germinate best between 65 and 70 degrees
• Direct seeding into the garden is not recommended
• Dahlias are a warm weather plant and will need to be under grow lights when emerging and growing on
• Dahlias will bloom in about 100-120 days from germination and can produce tubers in the same growing season
• Transplant into your garden after the danger of frost has passed and the nighttime low’s are 50+ degrees

Now let’s really get into it!

Germination with the Paper Towel Method

I like these 4×6 photograph storage boxes. They don’t seal completely so they help regulate excess moisture.

By far the most successful method for me is sprouting dahlia seeds between lightly damp paper towels. This method lets you have a look at the whole process and control all the variables, leading to a higher percentage of seeds that germinate. With dahlias having a lower germination rate this also helps save on space so you aren’t staring at a cell tray filled with potting soil waiting for seeds that might have rotted and won’t ever emerge. I like to label and date my seed paper towels before dampening so I know when those seeds were started and what mix they might be.

About 4-6 weeks before your last spring frost, lay seeds out on a lightly damp, fully squeezed out, paper towel, folded over once or twice. Be sure the seeds aren’t piled on top of each other, but spaced out a bit not touching. I prefer shop towels as the fibers are denser and hold moisture longer. I have spring fed water but if you are on city water or your water is treated heavily, I would recommend looking into using bottled spring water. I have in the past germinated seeds with chlorinated/treated water and the germination rates were much lower.

Once you have your seeds in their damp paper towel packets you’ll need to store them in a container so they don’t dry out. There are a few options but I will go over my favorites. The first is the good ole plastic zip baggie. Easy to store, easy to label. Some other options are a glass dish with a lid, a plastic container like those for 4x6 photo storage, or if you’re germinating on a large scale you could use a 1020 tray with a humidity dome on top.

Place your seeds somewhere warm and out of direct sunlight. Dahlia seeds prefer temperatures of 65-70 degrees. Too cold and they won’t budge, too hot and you risk damaging the seed. I germinate my dahlia seeds in my house, which in the early spring tends to stay on the cold side, around 62 degrees. I find setting your bags/containers somewhere warm like the top of the fridge to work well. If you are germinating them in a really cold area you could use a seedling heat mat but make sure it is the kind that you can temperature control, or purchase a separate controller to keep the temp between 65-70. The seedling heat mats I have, if not controlled, can get up to 80 degrees which is far too hot.

How long does it take for dahlia seeds to germinate?

It can vary from seed to seed but generally speaking, expect 3-5 days for some seeds, others could take 10-15 days. I’ve had some seeds sprout after 23 days! After around two days you should notice the seeds plump up. As long as your seeds are still healthy looking (no mold, and not rotting) it could just take a few extra days for the last few seeds to sprout.

Check your seeds at least once a day, twice if you’re like me. I personally love making my coffee in the morning and opening up my paper towel packs, examining the seeds and rooting for the stragglers, just waiting to see a tap root pop out of the seed casing.

A few things to look out for - Mold and Rot. Both of these things can be mitigated but are enemies of healthy seeds. Mold can grow pretty quickly but checking your seeds daily can help spot it before it becomes an issue. If you notice white or pink or any other color mold starting to coat your seeds, fill a spray bottle with water and add 3% hydrogen peroxide. Lightly spritz the seeds and this should help. Rot can be caused by an excess of water. If you notice your seeds starting to rot or look soft, or your paper towels are excessively wet, change them out. As practice, I usually change out my paper towels every 5 or so days, more frequently if they start to get too saturated or discolored.

Transferring sprouting seeds to potting soil and growing on

Your seeds have started sending out taproots! Yay! Now it’s time to carefully transfer them into potting soil. Depending on how many seeds you are starting, you can either put them into cell tray packs or small 3”-4” pots. I tend to start into cell trays and like to pot up once more before planting out. We’ll get into this a bit more below. It can be tempting to pop the just barely emerging tap root into soil, but I prefer to wait until it’s clearly broken through the casing. The two photos above show the taproots just emerging and ones that were left in the paper towels for an extra day. Both of these stages, and in between, is a good time to get them into potting soil. If you plant them sooner you risk your seed rotting. With care, place your seed into your preferred potting soil (I’ll list my faves below). You want the potting soil to be moist but not saturated. Again, excess moisture and rot are not our friends. Since the size of each seed can vary from variety to variety, a good guide point for how deep to bury dahlia seeds is sow the seed the same depth as the length of the seed itself. I typically do no more than 1/4” deep. If the tap root is longer, be careful it doesn’t get damaged and bury it downward - the way it naturally wants to root. Covering your potting soil lightly with fine vermiculite can help keep in the moisture as your seedling roots. Using a humidity dome - or draped plastic wrap but not touching the seed leaves - can also be helpful, especially if your growing location is on the drier side.

Dahlia seed leaves (cotyledons) 3 days after transplanting — Seed leaves (cotyledons) 3 days after transplanting

Dahlias prefer a good amount of light to grow strong. Once you transfer your seeds, place your pots or trays under grow lights for about 12-14 hours per day.

You can expect to see the seed leaves (cotyledons) emerge within a day after transferring the seed. Each plant can vary with how fast they grow but expect the first set of true leaves to emerge within one week or so. Once your seedling has a few sets of leaves you can lightly begin fertilizing your seedlings. I like a quality fish emulsion, diluted to half strength for the first few feedings. I typically feed my dahlia seedlings every 2 weeks. I don’t feed them full amounts of fish emulsion until they are planted out in the garden.

I like to start them in smaller cell trays then when they reach 2-3 sets of true leaves, transplant them into 4” pot to continue growing before planting out. When I pot them up I will carefully pull off the bottom set of leaves and bury the seedling a little deeper. This encourages roots to grow from the stem. This also helps encourage good tuber development later in the season. When growing dahlias from tubers, we generally plant them around 4”-5” deep. Since dahlia seedlings don’t have tubers yet, their roots are much higher to the surface. To encourage good tuber production we want the root ball roughly at the same depth as a tuber would be planted. If you haven’t potted up your seedlings into larger pots before they are transplanted planted out into the garden, you can do the same process of pulling off a set or two of leaves and burying the root ball at 4"-5” directly into the garden soil. At this point the seedling might have started to develop little tubers. So cute! Seedlings, like cuttings, don’t always produce abundant tubers in the first year.

Dahlias prefer not to be under 50 degrees so wait until your spring/late spring night time lows are consistently 50 degrees. For our growing region (7a) this is typically in mid-May, right around Mother’s Day. I space my dahlia seedlings to 12-16” apart in the garden. You could go wider (18”-24”), but I find with seedlings, they can stay on the smaller side in the first year. Just as with tuber grown dahlias, I recommend supports as the plants are growing. It’s best to put these in at the time or planting so you don’t accidentally harm the roots or tubers inserting stakes or t-posts midway through the season. Once the seedlings are in the ground, I will go back to a full dilution of fish emulsion, feeding weekly. I will switch to a compost tea or bloom fertilizer once they begin to bud up.

This is my favorite way to transplant sprouted seeds. I start at one end of a 72 cell tray, filling the cells as needed. Each seedling gets it’s own tag with any information I want to keep such as who the seedparent is or what the date of germination was.

Now we wait for surprise blooms!

After such care and nurturing, it’s so exciting to watch dahlia plants grow and grow, budding up around 90 days or so and blooming within 120 days. Around mid-summer, one of my favorite joys is walking my seedling rows in the early mornings. Dahlias have such complex genetics that the combinations of bloom color, form, and size are so vast! While one of the strongest genetic trait is an “open center”, starting with seeds from fully double blooms will increase the percentages for double bloom seedlings.

A 2023 favorite seedling. A cute lemon yellow ball shape with delicate pink petal tips as it unfurls.

What makes a good cut flower dahlia?

If you are growing dahlia for cut flowers, here are some things I look for when evaluating a dahlia seeding bloom. Chances are all dahlia blooms are going to be beautiful, bringing joy and brightness into your garden and vase. Double blooms are what most cut flower farmers and floral designers are looking for. I first look at the bloom itself - how many petals does it have? I’m looking for a densely packed, high petal count.

Next is the direction in which the bloom is facing. If it’s leaning downwards that’s a no go for me. Front facing, or clock face, dahlias can sometimes be nice but for me, there needs to be something special about the bloom color or shape. Ideally, I’m looking for dahlia blooms that are facing slightly upwards making them great for design work.

Is there strong bloom to stem attachment? Give that dahlia stem a good shake! Is it solid? Does the dahlia flower wiggle around or fall off? Some movement is okay but if it seems weak or is flopping around on the stem then that isn’t as ideal. Stem thickness is also a trait I evaluate. Is it a strong sturdy stem? Does it bloom on a long stem or is it stumpy? Is the stem too thick? This can sometimes be less desirable trait to floral designers as it limits the number of blooms that can go into a design.

Vase Life - I look at vase life of a bloom and if it “blows open” showing the center. Dahlia’s aren’t a long lasting vase flower. Not all dahlias will have the same vase life and I find it varies from variety to variety. Ball shape dahlias tend to have the longest vase of life of around 5-6 days while more open forms like waterlily dahlia blooms have a shorter vase life of just a few days. These varieties can be wonderful for event floral design work.

Lastly, for me as a dahlia grower, at the end of the season before the plants die back from frost, I flag which plants I want to keep for the next growing season to evaluate. I will see if it produces good tubers and then watch those tubers through the winter storage to see how they do. Some will do great, while others will not. Sometimes dahlia blooms can shift in color or traits from one season to the next so it’s important to grow them for around 4 seasons to see if they stay true to their first blooms.

Seedlings hardening off, waiting to be transplanted into the garden

I hope this guide has been helpful! Wishing everyone all the dahlia seed success and beautiful dahlia blooms!

SCF’s Favorite Seed Starting and Growing Supplies

Below are links to my preferred supplies from my favorite suppliers. These are not affiliate links and I prefer to shop small when possible. I realize it’s not always possible for some supplies but community is an important part of my growing practice.

Dahlia Seeds
Our mixes are available for the 2025 season starting on 2/15, until sold out.

Potting Soils
Dirtcraft Organics (southeast US)
Fox Farm CocoLoco (nationwide)

Fertilizers
Brown’s Fish Emulsion
Fox Farm Big Bloom Flowering Fertilizer

General Supplies
Jump Start Seed Starting Mat + Seedling Heat Mat Thermostat (I recommend using these together)
Humidity Domes
72 cell 1020 Plug Trays
Cell Packs - This is a link to larger quantities - Cell packs can be found locally at your neighborhood garden center

If you’ve found this guide to be helpful, let me know what other topics on growing dahlias you’d like to learn about!

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Germinating and Growing Dahlias from Seed