I started trying to grow these from seed in early July, thinking they could grow enough to tolerate winter outdoors. I was told I didn't need to cool the seeds first. But none that I didn't refrigerate first sprouted. After refrigeration, it took weeks of moisture and sun to germinate. Lots of them germinated at the same time. You can see the two original leaves in the photo. They seem to pop whole out of the seed. The original two leaves have a total span (tip of one to tip of the other) of about one eighth inch. That is incredibly big for popping out of a tiny seed. But then those two leaves never grow! I moved it all inside to a south facing window and kept it watered. Each sprout stayed that same 1/8 inch size for many weeks. Finally a third leaf and soon after that a fourth appeared on most sprouts. At half inch span from tip of the 3rd to tip of the 4th, this sprout (in the photo) is the biggest and healthiest and first to start a 5th leaf (about 5 months after germinating).
Where I found volunteers outside, they got FAR less sun and less water. How do these ever get from seed to plant in the wild?

Maybe Jonna can help with this question. She is so knowledgeable on seeds and seed starting.
@JonnaSudenius

Hi jsf, and welcome. Could you give us a bit more information about what you've been doing with your seedlings?

What kind of potting mix did you use? Did it have any fertilizer in the mix? How warm are you keeping the seedlings? After they developed some new leaves, did you give them any fertilizer? How much water do they get?

The first two leaves that popped from the seed are known as cotyledons and they basically live off the food that is stored inside the seed until the plant grows a second set of leaves. On most plants the cotyledons don't get much bigger, as they aren't "true" leaves. They usually die off after a few weeks. Once you have leaves, the baby plants need bright light but not full hot sun yet. They also need a little bit of fertilizer once they have "true" leaves - use some soluble formula at about 1/4 strength at first. For a seedling that small, I'd use an eye dropper and count the drops. Increase the amount as you start to see greater growth. Too much will burn the leaves and probably kill the plant.

Since these grow naturally as weeds in the soil of my yard, I assumed they don't really need less acid soil nor extra fertilizer. That may be a problem. Maybe they would do better with fertilizer, but since they manage as "volunteers" I don't understand how what I'm doing is worse.

Most of the soil in my yard is decomposed pine needles and oak leaves. I selected soil with more long ago decomposed material and less of each of last year's pine needles, clay and sand.

Before and after they sprouted in Aug, I kept the trays outside all the time and moved them during the day to get more full sun than any spot in my yard gets and watered twice a day to keep them consistently moist but not drowned. As it got cooler I switched to bringing the trays in at night, then out during the day (during that long period only the cotyledons were visible).

Once it was getting below 32 outside during the day, I moved them to south facing windows in a cool room, where the nighttime and cloudy day low temperatures dip just below 50 and the solar gain on a sunny day gets them a bit above 70.

I'm watering every second or third day, now that there are significant roots to pull from below the surface. The soil surface gets dry in 3 days, but below the surface stays moist. There are openings at the side on level with the bottom of the dirt and I never water enough to get water to flow out of those, but just less than that.

Even with extreme care, adding water on top of the dry surface, it beads and runs around the surface for a while before soaking in. That momentarily puts the tiny plants under water, which I don't think matters. But it also washed dirt on top of the cotyledons of most of the plants, which stuck, so those plants have only the two leaves that followed the cotyledons visible. Even in five months, I don't think any of the cotyledons simply died off as you suggested. Most got buried. The rest never changed.

You implied true leaves continue to grow. I'm pretty sure they haven't. On each plant, each leaf has reached it final size before the next leaf started. Those final sizes vary. But each seems to definitely stop growing and the next leaf doesn't start until it has stopped.

In the photo, you see a leaf that was starting for a long time (after the large one before it stopped). Relative to the otherwise glacial pace of this plant, it then took off and in 9 days since the photo is almost as big as the smaller of two before it. I assume it will continue and be largest before it stops and the next starts.

I will be away the first week of April and won't have anyone to water them. Obviously the volunteers survive a week without rain frequently. I hope these are that strong by April. Maybe I need to move them to bigger pots in early March.

All these were from seeds from the white flowered campanula. All the volunteers except one were blue flowered. That one had two flower stalks when I found it, which I divided on transplant to two plants. Each flowered multiple times and then formed a large rosette still green through the severe weather. So I think I have two healthy white ones. But I prefer for nearly half the plants to be white. I expect all the volunteers I find and transplant in the spring will be blue. So these seedling may be required to get more white flowered plants (if they breed true, which is questionable)

So, you seeded in soil from the garden, with old decomposed stuff and not so many pine needles. That may be the problem. The baby plants are struggling to glean nutrients from that soil. Old stuff has had a lot of the readily soluble nutrients leached out by rain fall and snow melt (do you have snow? You didn't tell us where you are.) So the nutrients left are breaking down slowly and hardly feeding the little plants. The ones out in your garden have more organic stuff breaking down to feed them, plus they're growing slower or dormant (?) for some of the year and don't use nutrients at all then.

Try the weak soluble fert and see if they jump ahead with that. I think they will. I wouldn't pot them up until they're bigger. Don't rock the boat at this stage.

So what you really want is more of the white ones? Otherwise you wouldn't be going to the trouble of raising seedlings when these plants self-sow in your garden.

But unfortunately, you're right. The seeds from the white cultivar won't necessarily give you more white ones. Those flowers were undoubtedly cross-pollinated with the blue so you still will get a good proportion of blue seedlings.

The only way to be sure of getting white flowers is to buy seeds from a reputable grower. Then, when you've grown them big enough to transplant, if you interplant them with the blue ones they'll again cross-pollinate and probably sow more blue than white plants for you. You'll have to plant the white ones well away from the blue ones to keep the white strain going (although no guarantees a bee won't still cross them). The original plants will stay white, as long as they live though. Maybe get the mix you like of white and blue, then weed out the seedlings? Or let them put up first flowers and pull most of the blue ones?

This is the more successful of the two locations I transplanted into last spring. The two large rosettes at the top were the white ones. They annoyingly each moved 1.5 inch toward the other after flowering: All the rosettes died off during flowering (ones I transplanted, and ones I didn't). Then after the seed pods dried, each plant popped up a new rosette near but not exactly where the original had been. These two happened to each move toward the other, removing 3 inches from the separation I chose when I transplanted them (not a big deal, just a little annoying).

Snow: Winter weather here switches often between cold and dry vs. warm and wet. Most snow occurs during warm/wet and vanishes in a few days. Snow that fell during colder weather can last weeks. In a rare winter, such as a couple years ago, the snow fell mostly during cold weather, so the snow cover was solid until April. This winter so far has been the opposite extreme: Daytime temperature both below zero and above 50. Plenty of precipitation, but ONLY during warm spells, so the longest lasting snow cover lasted 3 days (shown in this photo on its last day).

This transplanted patch looks a lot less vigorous than rosette pictures others have posted. But they are doing much better than any of the volunteers I didn't transplant. Usually, campanula are just perennial, not evergreen in my yard.

13 days after the photo I wrote this thread under, it looks like the attached photo. As I expected only the newest leaf is growing. The two older leaves and two cotyledons are unchanged. The newest leaf has gotten a little bigger than the old second largest. I hope it is still growing and will exceed the old largest. For a plant that took 6 months to get this far, that is decent progress in 13 days. For a plant that might flower some year, it isn't yet encouraging.

The fertilizer I ordered should be here today. Hopefully that will make a dramatic difference.

The mature outdoor ones have made no visible winter progress. But I expect they aren't supposed to. I assume being green and unchanging above ground all winter means storing energy in some form below ground to create flowering stalks in the spring.

BTW, I added the tiny fragments of pine needles (you can see in this very magnified photo) as a semi-successful attempt to reduce the disruption of watering. Water tends to pile up on the surface pushing everything around (on this micro scale) before sinking in. The pine needle fragments help break the surface tension and make the water more willing to soak in.

Two weeks after the use of fertilizer, there is not any exciting change. The third leaf (top middle in these photos) grew a tiny bit, stopping at just a bit smaller than the second leaf and the fourth leaf has started (visible in this magnified photo, but not to the naked eye).

The fertilizer seems to have caused a green coating on some of the dirt (algae or moss, not yet enough of it to tell). I don't think I'm over watering. I hope that green stuff is doing no harm.

The many other campanula that are smaller than this one are also growing even slower than this one, so tiny as this one is, it is widening its lead. Some have a first leaf no bigger than the cotyledons and still have no second leaf.

Edit: Just to clarify things I mentioned before: These are indoors in trays in south facing windows, so they are only a little cooler daytime (and warmer nighttime) than the fall period outdoors when the mature plants have their big growth spurt, and they are getting more sun (except for filtering effects of clear glass) than any of the surviving outdoor ones ever got (the outdoor ones that got more sun died quickly).

Good to know, but as long as the weather stays cold you really can't expect a lot of growth. Once the sun gets stronger, daylight is longer and the ground starts to warm, you'll see them jump up and then be sure to start feeding them consistently.

Patience is the first thing you learn as a gardener, and after that to be an optimist.

Almost all of these that I grew from seed indoors died abruptly in early March. That includes all the larger ones, including the one I photographed repeatedly. The last few small ones, I transplanted outside in late March (because I would away too long to leave them inside unattended). Those are doing OK outside now, but no impressive growth.
The good bunch I transplanted a year ago and then protected from snow all winter are doing great and have a different leaf and overall plant shape than I had seen before. I should get a photo next time it is sunny. I had also sprayed repeatedly with deer and rabbit repellent, which seems to be required.
The worse bunch I transplanted a year ago finished dying off in the snow and nothing came back. Most of the volunteers I noticed in the fall (after bigger weeds covering them died off) also failed to come back. But I found a bunch of others that had trees providing better snow protection and were doing OK. I transplanted all those together into a spot adjacent to the failed transplant of last year. But I failed to understand the immediate need for rabbit repellent. Early the next morning I saw a rabbit finishing the overnight job of eating ALL of what I had transplanted.
Meanwhile, none of the seeds I planted outside ever sprouted.
Now I suspect rabbits may be the main reason most of the volunteer campanula I found last year grew in under LOTV. The rabbits don't seem able to pick out plants they want to eat (hostas, campanula, etc.) mixed in with LOTV. But destroyed my hostas last year right after I pulled the LOTV competing with the hostas, and destroy the campanula in my front yard wherever or whenever not protected by LOTV. I hope the repellent is what works on the patch in back (vs. some other reason rabbits don't go there) because that would mean it can save my hostas in front this year. But more likely, the repellent doesn't really work and something else about the location of the successful campanula transplants keeps the rabbits away.

I have found, in my experience, that they are very slow to get started. The ones that were most successful for me were the ones that I directly sowed in a shady protected spot with filtered morning sun. I just left them alone. I did not fertilize them or coddle them in any way. Once they were up, I would water them in the course of my summer watering.

After a couple of years, I transplanted them to a spot inside our fenced garden area that had mostly shade and filtered sun. They are just slow, but now they are doing well. Very easy, if I don't fiddle with them, moving around, etc. They have just been transplanted once. Since they are a bit crowded, I will space them more apart this coming fall. I'll just be sure to give them plenty of water during the heat of the summer.