Apple trees will grow very well in zone 9 California. I have no experience with apple trees in a humid zone 9 like Florida. Your seedlings should be transplanted out of the egg carton with the growth of the second set of leaves. I would suggest going into a four inch pot, each in its own pot. When the pot is well rooted I would go to a one gallon size. Next winter when the tree is dormant I would plant into the garden. Al

Agree they need to be out of the egg carton ASAP. 4" pots will be good for approx. 2-3 months for apples depending on your fertilizing schedule and will allow you to get them outside and properly hardened off. Plan on 8-10" pots for them by mid-summer and that will be good until next spring assuming a 3 month winter dormancy period at which time they can be planted in the ground.

Now, keep in mind that these were most likely a hybrid variety of apple (most store bought are) and normally grown from cuttings not seeds so the apples you end up with, if they survive to produce and if you have the proper pollination varieties also available will likely be quite different. What was the name of the specific variety? You will need to use it to determine the variety needed to cross-pollinate it.

Dave

Here is a link that might be useful: Pollinating Apple Crops

If it were me, I might be tempted to try bonsai for at least one of the seedlings.

Thank you so much for your information and advice. I will transplant tomorrow into 4 " pots.

I have absolutely no idea what variety of apple this was, it was so long ago. This whole project started as the result of my 5 year old son's curiosity about growing a new tree from the seed of the apple he'd just eaten. While it would be icing on the cake to ever get fruit, I'd be overjoyed just to have one of these trees grow to a respectable size and give some shade.

If I may ask a few more questions, what does hardening off mean ?

Will these plants go dormant here in Florida ? Should I still attempt to transplant into the ground in winter time here ?

Will the apple trees survive without a true freeze during winter ?

What sort of fertilization schedule do you recommend?

The limited information I've seen made it seem as if pesticides and growing apple trees go hand in hand. Is that true ? I'd rather not nuke these trees, and if they need pesticides just to survive I'm not sure the're the right tree for our needs.

Thank you so very much.

~what does hardening off mean ?

Plants grown inside have to be very gradually adjusted to life outside, the direct sun, wind, heat, etc. Takes a week to 10 days approx. Google the term 'hardening off plants' for details on how to do it.

~Will these plants go dormant here in Florida ?

Probably not. Depends on the part of the state. Takes several days of below 45 degrees.

~Should I still attempt to transplant into the ground in winter time here ?

I wouldn't. I'd wait till next early spring when it has some size and good root development. But you might ask over on the Florida Gardening forum here as things are rather unique there when it comes to gardening. And it will take some special work to grow an apple tree in Florida from what I have read.

~Will the apple trees survive without a true freeze during winter ?

Survive, yes. Produce blooms and fruit? Probably not.

~What sort of fertilization schedule do you recommend?

Any of the various fruit tree fertilizers should work fine. Just get it something that is well balanced.

If you Google 'growing apples in Florida' some good info comes up.

Dave

Thank you so much, I will google. I had been entering terms like apple seedlings and getting lots of information on germination but not a lot of help regarding what to do next, all of this advice has been so helpful.

I am glad to hear that growth can be expected, even if blooms and fruit cannot. If I get success and health I may drive them up north to my family and let them attempt to plant them into the ground next spring.

Google Johnny Appleseed!