I started some seeds indoors for this - they have sprouted! I've seen pictures of the tubers - how many years do you suppose it will be before they fully mature?

My babies,

WOW.
A clean success!
It will be a few years till you can really enjoy the blooms, but it's worth.

yeah for the strong babies!!!

Thanks I lost so many seedlings to damping off this year that I really relish my successes. I'm not sure about when to transplant them though. They don't look like they're going to get a second leaf.

Nice! Dora! Are they a true lily or are they a perennial which is called lily?
I have never grown them.

They are an Arisaema. Asiatic species are often called cobra lilies, while western species are often called jack-in-the-pulpit. So they are not true lilies even though they form a bulb. I got the seed from Gardens North.

Yup... there's so many plants called LILY...
I would say keep them in that pot as long as you can. Even till next year.
You never know how hardy these really are...and you are in zone 3? Would an "adult" one survive your harsh winter?

According to the vendor it's hardy to zone 3. The area I plan to put them in is quite sheltered as well. So I guess I'll find out if the vendor knows what she's talking about.

The soil in the tray is about 4 cm deep. Do you think that will be enough to keep them happy for another year?

Otherwise I agree with you about the dangers of premature transplanting.

My philosophy is the opposite. I like to transplant stuff as small seedlings.

Do you plan to grow them in pots forever, or in the ground? Leave them outside for winter, or bring in the house? Outside their chance of winter survival would be greater in the ground.

If you plan to grow them in the ground, I'd transplant them soon, after danger of frost. They would have all summer to sink their feet in and establish in place before winter.

Karen

I plan to grow them in the ground eventually. It's easy enough to winter in a pot if you bury the pot in the ground as long as the pot has as drainage. I can also test out different growing sites and see where they do well without putting them through the stress of transplant.

I've lost a lot of baby perennials by transplanting out too soon. They get buried in compost and die, or they don't really like where I put them and they die, or I forget what they look like the next year and weed them out and they die. Or they just ... die.

These aren't wintersown, but I have found with wintersown in particular I have more success if I leave it to the second year of maturity to transplant. Plants that are a bit bigger are harder to lose and look like something.

These grow from a tuber and it will take some time for the tuber to grow. There is a danger that they are too crowded--I might dig one up to see the state of the roots in a couple of months.

Yes, I also tend to plant when really young, but only in cases of plants I am sure are hardy.
But I have lost a lot of seedlings, cause I only go to my garden a couple of times a week.
IF I'm not there to water the seedlings, most of them DIE.
In cases with such plants... I think the bigger the plant, bulb, rhizome is... the higher chances of survival.
I also planted out in the garden two Arisaema that were supposed to be hardy at least one Zone below mine, and they died.
I'm thinking they were not big enough.
Maybe a 50-50% approach?
Like... plant half of them now, and keep the rest in pot?
I do this even with some hard to find seeds... sow half, and keep the other half till I see what goes on with the first half :)

I would still wait till late summer, even fall. Arisaema, as far as I can tell, don't have a long growing season. Your babies, I doubt they will produce another leaf. SO keep them as they are, take care of them, and when the leaves turn yellow, you can plant half of them in the garden and the other half spread out in the pot.

I haven't seen anything about a short growing season, but I suspect you're right. That will leave plenty of time before winter to transplant once they go into dormancy.

Resurrecting this old post!
I planted an Arisaema flavum I bought from Edelweiss Perennials June two years ago. I neglected it, it withered away and died. After taking "a year off" this year it showed up again, just a little thing. We have had the worst drought in recorded history (no rain since June here), and I again neglected it. However, before it "died" again it made a seed pod or whatever you call it, I just found it in the garden, the stalk had broken off. The berries are turning red, so I am hoping I will have fertile seeds.
Any advice on how to sprout them? I looked in Dr Deno's book, it sounds like he had best success at 70 degrees, less so with cold then warm but that did work too, so possibly winter sowing... Would y'all wait until they are all red and look mature, then clean and store over winter? Right now the cluster of berries is sitting on my kitchen counter.