Growitnow, I can't speak to the specifics of growing Platycodons, but I do grow seeds under lights for prolonged periods. You will need to provide greater root volume for your plants by having them in larger pots. You will need relatively bright lights. Some artificial wind from a fan or fans can make for healthier plants. Fungus gnats can become a problem (put a little Bacillus thuringiensis in your plant's water.) A buildup of urea and/or ammonium nitrogen can reach toxic levels. Nutrients with mostly, if not all, nitrate nitrogen are advisable. The calcium and possibly the magnesium in your growing mix will likely become depleted and some soluble calcium nitrate (from a hydroponics supplier) and a little magnesium sulfate (Epsom salts from a local drugstore) will be helpful. Be sure to dilute all soluble nutrients down to about half strength before applying them. MM

I forgot to put the tops back on my sprouts last night..(something about being knackered after digging and turning all day and 15 minutes in the hot-tub with a glass of Pinot). Anyhow, to my shock, we had a good frost last night. I checked on them at 6:30 when I got up..gently touched some leaves, and they were stiff! The surface of the soil was hard frozen. What did I do! Planticide! So, I ran around covering them all up, (like what good would that do), but, I figured the morning sun would warm them up quicker with the tops on. Checked them out at 11:00 am, and !!! they were fine! Sprouted basil got some blue spots on the leaves, but everything else (at least 30 containers) had not turned into cooked spinach. Yeah! Decided not to put them through that again overnight..so I put the tops back on before I 'tubbed' it!

I started my petunia's in winter and they did fine. They start out really tiny too. I agree on the painted daisy comment and yes biennials are like two year perennials. First year growth second year beauty. They generally reseed well. There were a few annuals that didn't mind the cold for me and I started in winter/snow. Dianthus, poppies, alyssum, viola's or pansies and petunias. In my z.5 I had to wait till frost was past for cosmos, marigolds, morning glories and four o clocks.

Marg.. I plant the boxes indoors around mid April.. when I see several spears appears I move them OUTSIDE into a cold frame. That frame is a rectangle of old storm windows that is only around 28" high... 5 x 10' for dimensions. It is screwed together tight.. will make 70's F even on a 40's day.. with sunshine. On warmer spring days the top must be left partially open to avoid overheating. 90's inside is my goal... the 30-40 shoe box containers warm and hold a good deal of heat. One electric heater keeps the temps from freezing on the coldest nites. One could go a step further and make the floor area capable of holding more heat... cement brick etc... rocks. I do not soak seeds.. this is for over-dried poor quality seed. Mine are stored the winter in the fridge at 40F... I get over 90% germination on most crosses... a few have made 100%.. this for 80 some seeds. I have tried soaking some over dry crosses.. ones that I have purchased.. crosses from plants that produce sub par seeds. I am not sure this helps.. goes to what kind of mix you use for starting them. My mix is reused annually.. a combination of good heavy soil AND some agent to lighten that mix and allow air in the soil. That is important.. too soggy makes for poor germination.. I've used coarse vermiculite, stryofoam via the bags I get at Lowes or Menards-- this used in concrete construction. I make sure the mix is wet enough... but not soggy.. learned from experience. I cover the plastic shoe boxes (come with lids) I use.. having adopting the use of these containers from Melanie Mason's routine. I do not make drainage holes in these boxes.. the watering routine making sure to avoid getting too wet.. easily learned as the containers are clear color for soil observation. Lids of course are off when germination is well underway.. make sure NOT to allow the seeds to dry.. lite watering frequently is best. I read comments per 'raisin seeds'... not good quality. Either harvesting too soon... from poor seed makers.. and/or over drying. W/O measuring them.. seem to remember my boxes are 10 x 14".. max planting density is 81 here.. 9 rows of 9. At least one inch deep.. think mine go deeper most often. With some care one can tip the box over on a side and usually get the whole mass out w/o too much trouble. If your planting different crosses in rows... trim the tops in a pattern for indenification should they get mixed on the tip. I also have used paints for ID prior to tipping. With the airy mix I use shaking the plants apart is pretty easy. My soil dries each yr in the garage.. bone dry.. I get no pests at this stage. Use the tree drench when watering early on it pests appear... that concentrate at 1/2 TBS per 2 gallons. I use a lite dose of Peters fert at each watering.. around 1/4 strength starting out... maybe 1/2 strenght later on. THIS YR.. I am going to stradify some seeds/boxes.. their ready now. Planting the seeds just before freeze up.. covering and/or burying the covered boxes with soil.. set in a shaded area behind trees to avoid overwarming in thaws. A friend in NY z4 uses fall planting.. and sez 95% or so of what germinates in cold hardy. I am going this direction.. albeit in stages. I lack the acres to do it much different.. space at a premium. But in the end my routines select what works well in z4.......