How to Grow Dahlias From Seed

Growing dahlias from seed is such an amazing exploration. You truly get to experience the full life cycle of a plant. If you have already grown dahlia tubers, growing dahlias from seed is a totally different experience. The seeds will require a bit more babying than just sticking a tuber in the ground. But the results are well worth it as you discover never before seen blooms.

Now let's get into the nitty gritty! This is the method I use, which I learned from Kristine Albrecht’s wonderful book, Dahlia Breeding for the Farmer-Florist and the Home Gardener. It is by no means the only method, but it works for me!

Figure out when to start.

Dahlia seedlings are more susceptible to frost damage than tubers are, so I plant them 1 to 2 weeks after my last frost date. Any frost will totally kill your dahlia seedling. I have found it is better to plant a larger plant later, than stick a smaller plant in the ground before the temperatures are safe.

So once you know the date you want to plant your dahlia seedlings, you need to work backward to figure out when to get started. Don’t start too soon! Especially if you are growing a lot of seedlings, the dahlias may quickly take up more space than you have if you need to repot them before the weather is appropriate for planting outside. Six to eight weeks before planting is a good time to get started.

Germinating your seeds.

Dahlias seeds are expensive and have a very low germination rate. Germination takes anywhere from 2 to 21 days. So the point of this method, while it may seem finicky, is to ensure as many viable seeds germinate as possible.

Dahlia seeds need two things to germinate, moisture and warmth. You'll need Saran Wrap, paper towels, and a warm location.

Throughly rinse a stack of about 15 half sheets of paper towels and wring them out. Now lay a couple sheets on the plate. Scatter about 25 dahlia seeds on the sheet and cover with 2 more paper towels. Repeat this process until you have about 5 to 7 layers of seeds. Cover with 2 final sheets of paper towel and tightly wrap with Saran Wrap.

Now you'll need to place your plates in a warm location that stays about 72 to 75 degrees, such as a stove with a pilot light, the top of a refrigerator, or a grow mat. Use a thermometer to make sure the temperature remains steady. Too cold and the damp seeds will rot, too hot and they'll cook!

After a couple days start checking on your seeds. You can also use this time to give the paper towels a spritz if they are getting dry. Once you see a little root cracking through the seed, it's time to plant!

Planting your seeds.

I use a 72 cell tray for this step, but any small pot will work. It is a good idea to prepare your tray or pots with moist soil at the same time that you warm up your seeds. This way the tray will be ready as soon as the seeds sprout.

Dibble a small hole into the cell with a pencil, gently place the seed in the hole ROOT DOWN, carefully firm the soil around the seed with your fingers, and very lightly water. A teaspoon of water will be sufficient to sett Leave about half the seed sticking above the soil line. Within a few days the first leaves will sprout and it is time to get your tray under grow lights or in a greenhouse. Make sure the temperature stays around 72 degrees and water as needed. Do not let the soil dry out! When your plant is about 4 inches tall, it is ready to go outside! But you can always transplant to a bigger pot if the weather is not yet appropriate for planting.

Planting your seedlings in your garden.

Before you plant your seedlings in your garden you must harden them off over the course of a week to get them ready for the outside world. Set them outside in a sheltered location (not too much wind, not too much afternoon sun) for just a couple hours. Repeat this process every day, slowly increasing the amount of time they are outside.

Now plant your seedling! Make a small hole in a sunny location, plant your seedling, and water well!

At this point you can start to treat your seedlings just like your tuber grown dahlias: use Sluggo Plus regularly, pinch when the plants are about 8 to 12 inches tall, support the plants with stakes or rope, and fertilize and water regularly. Make sure you harvest your blooms, so your plants continu

Wrapping up the Season.

Now that you have created a garden full of never before seen dahlias, you have to decide what to do next.

Of course, not every variety will be a winner. Maybe you don’t love the color or the form isn’t ideal. But they will all feel special because they are YOUR creations.