Sorry, I'm unfamiliar w/ this Plant.

Why not try a search by its botanical name which you have & see what results?

Hey Squidy..Yep, Windmill Palms can be grown indoors.
Congrats on getting seeds to germinate..it took a year?

When plants are grown in containers, they don't get as large as planted in-ground. 'Tree-Types'

Also, indoors, palms are slow-growing.

How small do you want it to be?

By keeping underpotted, a palm will grow slower and only get yay high.
Even if you repot into a larger pot, it'd take years before outgrowing your ceilings.

Since your seedlings are doing well, continue watering as usual. How tall are the seedlings and are they covered in plastic? Toni

Morning Squidy..What pot size would I recommend?
Do you mean after your palm is mature? I'm 'guessing' 10".
One of my palms, 3 varieties in one pot, have been in the same 10" container 10+ years. It's stands 3-4' tall, exceedingly rootbound.

But, don't transfer your seedlings in a pot this size..
Squig, palms are slow-growing. Last year I bought a variegated Palm, 'can't recall its type right now,' that I potted in a tree pot..The diameter is approximately 4", length/height 18".
In a years time, it grew 3 new leaves..lol..I hope its roots are growing. 'love variegated plants.' I bought two other small/seedling palms this spring; both are in tree pots, which may or may not survive.

But I want my palms to grow taller. If you want yours 'X' high, repot according to rootball size. Usually 1-2 sizes larger than the rootball. After roots are established, a 4" pot should do for a time. Gradually, 'as roots continue growing,' increase pot size until your Palm is in a 10" pot.
Since you don't want your palm too tall/wide, keep roots snug by keeping underpotted.

OR, you can always prune roots and leaves to desired height. But, we're jumping the gun..lol..Palms are unlike annuals... germinate in days, and ready for a 4-6" pot in mere weeks.. lol

Oh great, not a year..Did you use bottom-heat to speed up germination? The reason I asked...I recently received Bottle Palm seeds..'Bottle Palm plant is super expensive.' I'm waiting for Begonia seeds to arrive from Austrailia, then sowing together.

Time probably differs according to palm type, but it's said, some seeds can take up to a year to germinate. Since I thought yours took a year confirmed length of time correct. A YEAR!!
I'd rather not wait that long..lol.

Roots are important. Without roots there wouldn't be leaves. Don't peak..lol. Let them do their thing w/o disturbing roots. People who peak usually lose their plants. lol.

Western Window..Most Fan-type palms require bright/direct sun; other palms scorch. They don't need as much humidity, either..

There's a guy in Chicago, Il, another in Canada, who grow Windmil Palms in their back yards, year round.
Do you have a cool room in your house..'winter?' Toni

Thank you very much, all this information is helping a lot.

I did not use a heat pad or anything special. I didn't know about any of that, I just soaked them overnight and put them in a pot and kept the soil moist from then on. But I had just plucked these seeds off a tree in a parking lot on a whim, I didn't pay for them or anything. I had no idea if they'd germinate. And I have already disturbed the roots twice.. once when I was going to toss them because I thought they were dead and was surprised when I dug up some sprouting seeds, and once when I repotted them. They seem to be very tolerant to my inexperience, lol. That's probably why they can grow here in WA in very non-palmlike conditions.

The window they're in really isn't like a super harsh sunny window, it's just one of the sunnier ones out of my selection of not-especially-sunny windows, lol.
And are you saying I should keep them cool in winter? (Don't they grow in places with more mild winters too?)
Also, what do you mean by "tree pot", is that different from a normal pot?

Good luck with your bottle palms, I googled it and they look really cool!

This is a very popular tree with the guys at the palms forum. I would repost your question over there. And I wouldn't worry about these guys getting too big too soon. They are slow growers and indoors I would think they would be even slower. I have had two of them for about four years and because I got them when they were small they really haven't grown too much. They are extremely tolerant of cold so they would do well outside in your area too.

Squidy, sorry I never got back. In summer, I'm very busy outdoor gardening and hauling house plants outside.

Hope you're still around GW.

How's your palm doing? How large is it now?

By tree pot I mean....

{{gwi:91970}}

Tree Pots come in different sizes. Notice their height? They're not wide, but roots have enough room since pot is long.
Two small palms I purchased 2009 were placed in these pots, and doing fine. Especially variegated Rhapsis.

Like Aloyzius said, Trachycarpus fortunei is slow-growing.
If you visit the Palm Forum search for Trachy growing in the ground, outdoors year round, in Chicago IL and Canada. Toni