I was a little late starting my gardening under lights this winter, I like to start some perennials in the fall so they have a jump on the season and are closer to blooming the next summer. But I was having a problem with aphids coming indoors and infesting plants under my grow lights which are by an outside French door, so I moved all the plants out and tried to wash the leaves off regularly to get rid of them. And I left the grow shelves empty for a while to try to get rid of any stragglers. I think at least in the case of my aquaponics system (where I can't use pesticides, even natural, because of the fish) by a sliding glass door that was wiped out by aphids last year, that large black ants were actually carrying the aphids in. I try to stop bringing in plants at the end of the growing season, frequently they have aphids.
So here are my tomato seedlings, started Feb. 7 in small beading ziplock bags with wet paper towel inside, and the sprouted seeds are then planted into individual pots. I used to start tomatoes 4 per expandable Jiffy peat pot. Sometimes 4 would sprout, sometimes only 1, the range to come up was from 7 days to as much as 31 days. Long ago I even kept the 4 plants growing in the one peat pot until planting out in spring, and they did go on to make tomatoes OK. Then I tried sowing into pots with soilless seed mix of 1/3 peat moss, 1/3 perlite, and 1/3 potting soil, sterilized by cooking in a microwave for 10 minutes. Next I tried sprouting seeds in ziplocks and transplanting seedlings to 2 1/4" pots to give the seedlings lots of room and cut down transplanting. With ziplocks I wait until the little sprouts are 1/2 to even 1" long and plant directly into 2 1/4" pots, then later sometimes into 4" pots if they get too big under lights for my shelves, about 11" tall, or if I have to hold them longer without planting out. I get a smaller incidence of stuck seed coats this way, and less time wasted on preparing unnecessary pots for seeds that don't germinate, etc. There can be a problem with the occasional seed that wants to wait 31 days to sprout, but usally germination is faster in ziplocks.
I use my treasured 2 1/4" rose pots for all my seed starting, I originally acquired a good supply buying up mini roses for $.50 when Justice Mini Roses quit business. Unfortunately most of those roses are not around any more, since rabbits seem to like to eat them to the ground in winter. When I started needing more rose pots I found Anderson Die and Mfg. Co. was in Portland and wouldn't sell retail but with a business license I could buy them wholesale, a box of 950, #1680. So now I have a supply and reuse and bleach them when needed. As long as they are not in the sun they last for years. The whole advantage of the rose pots is that they fit 9 rows across and 4 deep in standard flats that are around 10" wide and 20" long, and flats fit 2 to a shelf on my metal shelves that have 4' fluorescent fixtures suspended below 2 shelves and plants on the 2 shelves below. The lights do extend past the ends of the shelves, and the flats stick out past the ends of the shelves, but it works. It doesn't take up much floor space and can be stuck in a closet or along a wall. With 4 flats of 36 seedlings, one unit holds 144 plants! I've had 4 shelf units going at once. Once plants are in 4" pots fewer fit.
Here are some of my perennial seedlings, this is a group of several kinds of Agastache- A. nepetoides, A. mexicana 'Sangria', and A. anisata, with A. hybrida 'Astello Indigo' and A. rugosa just germinating. They are in the mint family, generally with anise = licorice scent/flavor, many are native to the USA (unlike Mentha which is mostly introduced), many will bloom the first year from seed and come back the next year, and they can be used for tea. They range in size from 12-18" to 4-5'. Butterflies, bees, and other pollinators are attracted to them, and hummingbirds like the orange or pink ones. Deer did bite off the buds on some of my A. rugosa last year but left some A. rupestris alone, but deer are hard to predict.
I generally try for 9 seeds to a little pot, since germination is uncertain and I can generally handle that many seedlings and up for transplanting. I don't cover them with plastic like is often recommended because I had trouble with mold in that situation, but I do mist them with a hand sprayer 2 or 3 times a day. Here is a typical pot of seedlings, I wait until they have true leaves and are a little developed before transplanting, these Platycodon 'Hakone' double blue Balloon flower seedlings are about 1 month from sowing, coming up after generally 7 days. My computer is not playing nice so I couldn't rotate this-
Platycodon is an interesting plant, some I grew before are still alive several years later but overrun by other plants so I don't see them bloom much. They have a fleshy root used in Chinese medicine.
To transplant I first put my middle finger over the center of the pot and invert them into my hand, then break apart the little seedlings gently, hopefully keeping some soil on the roots.
I fill 1/2 of the pot vertically and press the soil, then hold the seedling by the base and line up the root junction with the top of the soil, the add a couple of tablespoons of soil at a time and backfill the other side.
The finished seedlings vary some in size, the smallest ones may not make it, but generally plants are like computer programming, if the conditions for growth are met they grow. Seedlings that have died on me generally needed sandy rather dry conditions or alkaline soils, and were too wet. Or died from not being watered enough when things got too busy, or so many plants make it hard to see which ones need water.
Well, what are you growing under lights?
Happy 2/3 winter, Hannah