The paper towel method uses damp paper towels in a warm (usually) space to germinate seeds. Once germinated, sprouts are transferred to prepared seed trays for growing. Pre-sprouting dahlia seeds using the paper towel method works really well for us. The paper towel method allows us to germinate lots of seeds in a small space and creates a situation where we are not wasting any seed tray space on seeds that won’t sprout. As a bonus, all seedlings in a tray are about the same age, so growth across the tray is more consistent. We live in a small 700sq. ft. house, and do not have any insulated/heated greenhouses. All of our “before last frost gardening,” like starting dahlia seeds and taking dahlia cuttings, is done on a three foot wide, fifteen inch deep, four shelf wire rack in our living room and growing on/maturing is done on a covered rack on our porch (with lights and heat mats) so saving space and growing efficiently is really important for us!
Materials I use to pre-sprout dahlia seeds:
· Dahlia seeds
· Cookie tray (plate or platter also works)
· Paper towels
· Plastic wrap
· Garden marker
· Plant labels
· Seedling trays with humidity dome
· Seedling medium (I use coir/perlite/vermiculite)
· Grow lights
For each variety, I fold a paper towel in fourths, then moisten it with water. I squeeze out the excess water so that it is not as squeezed out as possible but isn’t dripping wet either. I write the variety on the plant label and place that in the middle section of the paper towel along the fold. I then place the seeds on the damp paper towel and fold the top over so the seeds and label are sandwiched in the middle. I continue this with each variety and stack them on the baking sheet. When all the seeds are in their little paper towel “books,” I cover the baking sheet with plastic wrap and set it on my indoor shelves. I do not use a heat mat for this, but since the shelves are in our living room, next to the woodstove, I estimate the tray stays between 60-80F.
I use the 3 foot lights inside and the four foot lights outside; nice and bright, easy to set up, easy to switch on and off
Dahlia seeds have a wide window of when to expect sprouting, so it’s best to have your seed trays ready once all your seeds are in their paper towels. We had 80 seeds sprouted and ready to transfer to trays on day two this year and another 60+ on day three! I am using 40 cell trays that fit well on my shelves and I am filling them with a coir/perlite mix that I combine with some vermiculite. I will up-pot seedlings to 4” pots once they are growing well, so a soilless mix works well for this first tray. This tray gets filled with medium and watered well in preparation for sprouts. I begin checking the seeds on day two and check each little “book.” Any seeds that have a root tail poking out of the seed coat are ready to be planted! I poke a small hole in the center of the cell (pencil, dibber, etc all work for this) and carefully place the root end of the seed in the hole. Holding the top of the seed (or leaves if the seed coat slips off), I gently firm the medium around the seed, so the root is in the medium and about half the seed is poking up vertically out of the medium. I then write on a label with the variety and date and put it in the cell with the sprout. Once all of the sprouts are done, or the cells are filled, the tray gets its humidity dome on and it goes to the rack with grow lights on. I am not suing heat mats for these, as the don’t really need it in our space. I move the humidity done on and off as I feel it’s needed. I’m not scientific about it, and I prefer to err on the dry side after the first 48 hours or so.
It's important to monitor moisture in the trays and water as needed; little sprouts can dry out fast! Keep them as close to the lights as you can, so they don’t get leggy (tall/thin/weak). The seedlings will need fed and moved to bigger pots as they grow (unless you started them in 4” pots). They will still need lights and to be kept warm until it is safe to plant them out (after last frost for dahlias). Our dahlia seedlings generally get large enough that we can pinch them before they go out to the garden, so they are nice and bushy and it’s one less dahlia chore to attend to once they are outside.
These labels come in different colors and are sturdy. I am using yellow for seedlings, pink for cuttings, and white in the field for tubers
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