What are some good methods for protecting walnut trees from the cold in winter?

Mounding soil for cold protection: For 1- to 2-year-old young trees that cannot safely overwinter in the open field, bend the entire tree trunk to one side and cover it with soil. This is the most effective and reliable measure to prevent winter dieback.

Hilling soil for cold protection: Build a mound of soil within a 30 cm radius around the base of the seedling to prevent frost damage to the root crown and graft union. Remove it in the following spring after temperatures have risen and stabilized, and level the tree basin.

Whitewashing for cold protection: Whitewashing young trees can ease the temperature difference between the sunny and shady sides of the trunk and gives good cold protection; it can be applied before the soil freezes. The whitewash formula is: 0.5 kg salt, 6 kg quicklime, 15 kg clean water, plus an appropriate amount of adhesive and residue of lime sulfur mixture, applied evenly over the trunk and branches of young trees.

Polyvinyl alcohol trunk coating: Use properly boiled polyvinyl alcohol to evenly coat the main trunk of the seedling. The boiling method generally uses a ratio of "polyvinyl alcohol : water = 1 : 15 to 20". First heat the water to about 50°C, then add the polyvinyl alcohol (do not add it after the water has come to a boil, otherwise the polyvinyl alcohol will not dissolve completely and the solution will be uneven). Stir while adding until it boils, then simmer over low heat for 20 to 30 minutes, and use it after the temperature drops to where it is no longer hot to the touch.