1) It is the beginning of being root bound. Unless you can get them outside into their summer pots/ground fairly soon, you will probably want to repot them in the mean time.
2) Eventually, the pot size will limit the plant although they will likely grow up to a foot or more tall in those containers before you get visible signs of stress. They will likely need watering more often as they grow larger.
3) I struggle with the pot size vs lighting just like you. I used to use 6" interim pots but once you go from 3" pots to six inch pots, your area of coverage more than doubles.

I don't know when you will be able to get your plants outside for the summer, but if it is within a month, you are probably fine. Otherwise, try to find some cheap 4-5" containers to repot to. I used the 3.5" starters this year to start with, so that I wouldn't have to repot from a 1" cell to a 3.5" cell and then a 6" cell before finally going to the 5 gal buckets for the summer. I am about 2 weeks behind you, but I have a good two months before I can get them outside even part time. So, I am going to have to repot at some point.
So far your plants look good. I hope this helps,
Bruce

Thanks again, Bruce.

In my climate, I don't expect to get these guys outside before the middle of May, maybe even late May. We still have snow and frost, and the average last frost date is May 14th. I was planning to harden them off in May, and get them in the ground late May/early June.

We get milk in 1 litre cardboard cartons. They're roughly the same size as my current pots (except much taller of course). I was thinking maybe I could fit half a carton (without the bottom) inside the small pots - that way I'd get them twice as high while maintaining the drainage from the pots. Will the increased depth be good enough for the plants, or will they be stressed anyway if the pots are too narrow?

The plants look incredibly healthy, especially for their age.

I doubt that the roots have actually filled the entire volume of soil at this point - more likely, the roots are simply chasing the moisture and air at the bottom of the pot. How do you water, by chance?

Josh

Thanks, Josh. Being inexperienced, it's very helpful to get confirmation that things are looking good.

I happen to water them from the top, simply because I don't have any practical way of watering them from below. I let dry out completely between watering, to the point where some leaves loose their firmness a little. No fertilizer yet, there doesn't seem to be a need for it, as they're growing steadily.

I guess you're right about the roots not filling the whole cups. But I kinda thought the roots mostly grew downward, and would stall if not given more depth to dive into. Will it buy me more time to eventually put them in taller (but not wider) pots?

This post was edited by cjohansen on Mon, Mar 11, 13 at 13:43

Sounds like you're doing everything right. I assume that typo means you water from the top not the bottom?

In a heavy mix, the roots stay to the outside and bottom near the drain-holes, because that's where the water and, thus, the air is found. Container depth/shape doesn't make much difference if the mix is well-aerated (the roots will colonize the entire soil volume if air and moisture are present throughout).

I think you can squeeze another week or two out of the small containers, and you can let the Jalapeno double in size before up-potting. If this were a commercial operation, I'd say pot them as soon as you see roots...but I don't think you're in that kind of rush.

Josh

Yeah, I water from the top (fixed the typo in my other post). So far I've been using a store-bought "pot soil with leca". It's supposed to be "nutritious and porous", but it looks a little heavier/denser than what I see on other people's pictures on this forum. Maybe I'll try mixing it with something lighter when repotting.

Worth mentioning: I have other plants (mainly Jalapeños and Ring of fire) roughly the same size as the Jalapeño I posted a picture of, but in small pots like the Poblano above. It's mostly a coincidence that three Jalapeños are in the big pots, as I had them from some store-bought herbs that were used up :)

My rule of thumb for container size is that you ideally want a container that allows as much space below ground for roots as the stems and leaves take up above ground. For a good visual, if you could take the pot and turn it upside down on top of your plant, would most of it fit?

From your pictures, I'd say you're fine right now, but you will definitely need bigger pots for them if its going to be another two months before they can go out.

Here's a picture that better shows roughly the size-range:

I have some Habaneros that are way smaller, but obviously they aren't a big concern.

I'll try potting them taller to see how that works. I don't have room nor lights to cover a larger base area. FWIW, the plants don't seem stressed yet.

I made a decision, and will attemp this solution: Repotting them to 50cl plastic cups. Doing the double cup setup that many others are doing: Poke hole in one cup, rest it inside another one, which allows for watering from below.

I've bought more growing medium, perlite, vermiculite and 100 cups. Looking forward to an all-nighter this week of repotting :)

I've potted up most of my plants. I went from a commercial "seedling mix" to a mixture of another commercial mix (mostly peat), vermiculite and perlite - a mix that is _alot_ lighter. So far, so good, the Jalapenos that I potted up two days ago are still very happy. Here's what they look like now:

My Jalapeños and Ring of fires are the bushiest plants so far, but somehow the hot wax peppers where the ones with the biggest root balls:

For some reason my Habaneros are lagging behind. I guess it's partly because they grow slower(?), but I'm going to start them on a little fertilizer next time I water them.