In principle, you can plant a walnut tree at any time from the spring to the autumn months. You can find out which variant is the best here.
A walnut tree can be planted in both fall and spring
Spring or autumn?
In principle, it should be noted that young walnut trees are very sensitive to frost.
Therefore, you should definitely avoid both the last late frosts in spring and the first early frosts in autumn.
spring
In spring, mid-April is good for planting a walnut. By this time the ground has usually already warmed up.
fall
In autumn, it is also important to only plant the walnuts when the soil is (still) warm.
Note: You can plant the walnut tree until mid-November, as long as the weather conditions are right.
Autumn planting has a decisive advantage over spring planting:
The walnut is still developing fine roots until permafrost sets in. This will make it easier for her to drink enough water next spring.
Attention: In regions where frost periods are common as early as September and October, you should prefer spring planting. Then you have to water the young tree sufficiently, especially in the budding phase.