When I first started growing flowers from seed for my cut flower business, I read over and over again 'don't start Iceland Poppies or Lisianthus from seed, it's too hard and takes too long. Just buy plugs and be done with it.' I knew that these two crops were so valuable as a farmer florist so bit the bullet and spent several hundred dollars to ensure I had them from a plug broker. But I also decided that seed was cheap and it was worth giving Iceland Poppies a go to at least compare seed grown and plug bought plants. Much to my surprise the seed grown Iceland Poppies turned out sooo sooo much better than the plugs I had bought! I received healthy little seedlings from my plug broker, but there were multiple plants to a cell, so I ended up having to trim out one or two of the extras per cell as I potted them up. Their roots were so intertwined that there was no way I would be able to keep all of the seedlings. And while snipping out the extras still gave me lots of little babies that eventually bloomed and were beautiful, the little seedlings had been competing with each other for nutrients and water at a really important developmental stage, and were really set back by the time I got them and potted them up. It also felt great to be sustainably growing my seeds and not having to rely on shipped plugs!
Meanwhile, the poppies I had started from seed were grown one to a cell and were not shocked near as much as the plugs were when I had to lift them and pot them up. Furthermore, Iceland Poppies, Reeally resent root disturbance, so being able to pop them out of their little cells, before they outgrew them, helped a lot with them not being shocked by being moved.
This year, I am forgoing buying plugs at all and will be starting Iceland Poppies and Lisianthus from seed only. In the shipment of plugs I received last year I also received Lisianthus plugs, and much like the Iceland poppies, there were several seedlings to a cell that were root bound and went through a period of shock when I potted them up, so I have high hopes that the ones I start from seed this year will take off quicker and be healthier from the get go.
So now a little info on how I grow Iceland Poppies and Lisianthus from seed, because it is an almost identical process for both. They both take a long time to be ready to plant out, they both like to be started on heat, and then moved to a cooler room, and they both can be planted out in early Spring before the danger of frost has passed.
Preparing the trays
To start, I prep my soilless mix using Pro-mix from Ace Hardware by wetting it down and working the water in with a trowel or my hands so that it is moist all the way through and there are no dry chunks. If soil is bone dry it repels water, this is called hydro repulsion, and it is almost impossible to fix after the fact. I then filled my 128 cell trays with soil, being careful to press it into the cells so there were no air pockets, but not so firmly that it would be hard for the delicate little roots of the seedlings to work their way into the soil. I then placed this tray into another tray that had no cells and no drain holes. This bottom tray is what you will use to water your seedlings from the bottom. The seed of lisianthus and Iceland poppies are so fine that watering from the top can disturb the top of the soil so much that they can end up too deep under soil or washed out of the tray!
2. Sowing the Seed
Now that the trays are prepped it is time to sow the seed! I find this process so relaxing. Since the seed is so fine it can be somewhat hard to sow evenly and lightly; a pencil with its end dipped in a tiny bit of water to pick up the seeds and place them precisely into the cells is a great trick! The lisianthus seed that I receive is covered in a protective coating that is water soluble and makes them easier to handle and pick up. Lisianthus needs light to germinate, but I find that scattering the surface of the tray with vermiculite after all of the seeds are sown is another great trick to prevent algae from growing and to ensure that the seed has good contact with the soil.
3. Bottom heat
So now that your seeds are all sown and finished off with a dusting of vermiculite, they are ready to be placed on something that gives them bottom heat! Heat mats are fantastic for this, but I live in an old farmhouse with dozens of radiators so I place my seed trays on these until they germinate. If you do use radiators, its a good idea to place a large floor tile or long piece of wood on the top to help with stability and to spread out the heat a bit more. The trays should be lightly damp from working the water in at the beginning so you shouldn't need to water them for a couple of days, but be sure you are checking that the soil is not drying out, especially since the heat will cause the soil to dry faster! At this important step if the hypocotyl (the first bit of green you see peek through the seed) starts to emerge because the water is causing the seed to swell and the hypocotyl to break through, but then suddenly it gets no water, the seed is no longer viable because the protective coat around it was breached, so all of the goodness inside of the seed will also have dried out! I like to keep a clear tray dome over the whole tray at this step, because it keeps the humidity up, and the soil doesn't dry out as fast.
4. Growing On
When you see the first tiny little leaves (cotyledons - not true leaves), remove the humidity dome and put them somewhere cooler. I usually like to set up grow lights in the coolest part of my house which usually ends up being a spare room/my office. At this point in the process it is a bit of a waiting game. Lisianthus have an irritating habit of going into a resting stage, the rosette stage, if the temperature gets above 75 degrees, it can last for a couple of weeks which can make it difficult to grow them to a size where they can be planted out, so try to keep them somewhere where the temperature is 60-65 degrees constantly. You will need to make sure the seeds stay moist, but not too wet. Since they are in a soilless medium and are starting to grow in earnest, it's a good idea to start giving them a foliar feed every week to every other week. I like to use fish and kelp organic fertilizer sprayed with a handheld sprayer or spray bottle. Be careful though, this is smelly stuff, so I do not recommend fertilizing them in the house. At around 8 weeks, they should have developed 2-3 sets of true leaves and are not as prone to rosetting, its not as critical to keep them under 75 degrees. This is also the point when you can pot them up into a larger cell tray; I like a 72 cell tray at this point. This whole process of babying them takes 12 weeks until they can finally be planted out in April in my Zone 6b garden.
While growing Lisianthus from seed is a time commitment and takes patience, I think growing them yourself, if you have the time and space, can be a really wonderful thing to do, especially if you want to spend less money on shipped plugs, get more and unusual varieties, and if you would like to have sustainably grown lisianthus, grown well!!