They are beautiful! Where I live, we plant in the Spring or the Fall. Mix good soil in with your existing soil when planting and water the baby trees a couple times a week the first few months. Mulch before their first Winter.

There used to be a great forum called QDMA Quality Deer Management Association. There were great posts on Chestnuts. This appears to have been discontinued. I think some have moved to the new forum below. In the United States, hunters/landowners grow habitat attracting food plots and nut trees to attract wildlife. Try searching "forum hunters chestnut" to locate good forums on planting Chestnut trees.

There is also great resources on Chestnuts through the American Chestnut Foundation. You will increase your search results on Chestnut growing if you search for the "Dunstan Chestnut". A blight resistant variety gaining great popularity with growers and hunters in the US.

To answer your question, germinated Chestnuts can be planted anytime. You should protect the tree closely outside until the Chestnut is removed since squirrels/mice/rats will destroy the tree to eat the remaining nut. I typically let mine grow all season and plant in the ground first Fall after germinating. Keep in mind they are highly sought out by wildlife and will be eaten down to the ground if you have deer or other foraging species. I would invest in some tree tubes if you are planting out in a wildlife area. Try this site below.

http://habitat-talk.com/index.php?threads/growing-chestnut-trees-from-chestnuts-transferred-from-qdma-forum.5676/

ootockalockatuvik - take a look at the photos. The OP's trees are not true chestnuts, they are Aesculus, which are toxic. Plus s/he is in Israel so I doubt deer hunting is a big thing.

Floral - I do not expect his/her trees to be American Chestnuts or the Dunstan hybrid, but expect them to be a Chinese or European variety. Cultivation from a chestnut is the same.

My references to deer hunting are in regards to Habitat Culture for deer including Chestnut trees. If you visited my links or perform the searches I suggested you will find a great deal of information on "Chestnut Culture" and growing trees from acorns, nuts, etc. There is more information in these types of forums on growing Chestnuts and Oaks from seed than anywhere on Gardenweb. My goal was to provide a bank of resources along with answering their question.

***Visit this link- A great forum post about growing Trees from Chestnuts.

http://habitat-talk.com/index.php?threads/growing-chestnut-trees-from-chestnuts-transferred-from-qdma-forum.5676/

Ootockalockatuvik, I am afraid you are mistaken. The OP's 'chestnuts' are not any kind of true chestnut be it European or Chinese or any other type. The common name is misleading. Just look at the pictures. Large digitate palmate leaves totally unlike true chestnuts. They are Aesculus hippocastanum, Horse Chestnut, not a member of the unrelated genus Castanea, or true chestnuts. They are toxic to humans, cats, dogs and horses and in my experience are not even eaten by wildlife. In addition the OP is in Israel so culture of any tree species will be climate and site specific.

Here's Aesculus hippocastanum growing in one of my local parks. Note the huge white blooms all over it. Nothing like any Castanea.

The OP's duplicate posting of this question on the Tree Forum is here.

Attempting to provide cultural information to someone who asked and received no responses. I did not see the duplicate post in the tree forum. Your picture looks great!. Looks like a great park. I bet an American Chestnut would flourish in that location.

The main use of 'chestnuts' is the time-honoured method of threading them on string and whacking the sh*t out of them in a game of conkers (as they are called in the UK). Various (cheating) methods have been tried in order to get the hardest and toughest skin...such as soaking in vinegar, baking in the oven and so on...but afficionados generally have a favourite horse chestnut tree which yields large, glossy and, most importantly, tough conkers. A victorious player will often retire their favourite conkers with an unbeaten score of many direct hits and a dozen shattered opponents.