How to Successfully Pot Up Seedlings & Dahlia Tubers
With spring fast approaching, there is lots to do here at the flower farm. We are busy prepping our beds, sowing seeds in the greenhouse and tending to seedlings. We are also busy potting up hundreds of seedlings in anticipation of our annual cut flower seedling sale. And then there are the dahlias. We are pulling last year’s tubers out of storage, dividing them, and for particular varieties that we want more of, we are potting them up as well so that we can take cuttings. We thought we would share how we pot up our seedlings and dahlia tubers.
Potting Up Seedlings
Psst…Save the date for our upcoming Dahlia Tuber & Cut Flower Kit sales! We will be selling high-quality tubers and seedlings starting March 23rd, 2024. Get on the newsletter to be the first to hear when it begins — and even get an early preview!
We grow our seedlings in propagation trays, some have 72 cells, meaning they can hold 72 seedlings, and others have 216 cells. These are great for starting seeds but once the seedling outgrows those smaller cells, if it’s too early to plant them out into the garden, they need to be potted up into trays with larger cells or into pots. I am transplanting them into 3-inch pots which allows them to grow to be bigger more robust plants. This process of transplanting from a small cell or pot to a larger one is called "potting up".
This is how we do it:
Step 1: Gather all of your needed supplies:
Trays
Pots
Growing medium
Labeling supplies
Step 2: Water your seedlings, as this makes popping them out of their small cells easier. It also helps to prevent transplant shock.
Step 3: Fill your 3” pots (or any size you want to use) with growing medium. I use potting soil for this. Make sure not to pack the potting soil in too tightly.
Step 4: Make a hole in the soil of the pots to prep them for planting the seedling. I use a pencil or my finger.
Step 5: Pop the seedling out of its small cell. The easiest way to do this without disturbing the roots is to use a pencil to pop them out from underneath the tray.
Step 6: This is an optional step, but I like to dip the seedling into a mushroom-based root inoculant (affiliate link, but it’s our favorite!) before planting into the pot. This gives the roots an added boost to grow.
Step 7: Then, plant the seedling into the hole you made in the pot and secure it in place by lightly mounding some soil around it. Repeat this for all of your seedlings.
Step 8: Don’t forget to label! I use painter’s tape and a Sharpie.
If you water your seedlings well before you pot them up, you can wait a day or two before watering again.
Potting Up Dahlia Tubers
Dahlias are a high-maintenance crop, but one we find very worth it at Sweet Earth Co. We normally pull the dahlias out of storage in February and March to check to see how they made it through the winter and divide them before getting them ready to plant in May.
If the tubers are mushy (which is a sign of rot) or have signs of disease, they go in the garbage bin (not the compost).
All others are divided from clumps into individual tubers. For more on dividing tubers, watch our tutorial.
There may be some dahlia varieties that we want more of, and we pot those up so that we can take cuttings.
We pot up our dahlia tubers in 4” pots in a mix of potting soil with the neck sticking out.
Then, once there are some sprouts, we take cuttings from some that are on their second or third set of leaves. We’ll snip off a set of leaves and pot it into another pot with potting soil, after dipping the cuttings in some rooting hormone (affiliate link) to promote growth.
When we replant these cuttings, we plant them near the edge of the container — we’ve had good success doing this, as it positions the roots nicely.
Once you see some new sprouts coming out of these, they are ready to transplant into your cutting garden. Dahlias grown from cuttings will go on to produce tubers that you can save.
You can learn more in our video about propagating dahlias.