Boil, then mash the potatoes.

Use a vegetable peeler to make long strips of cucumber.

Cut the cucumber strips in half, sprinkle salt and let sit for 5 minutes.

Rinse the strips in water (The photo only shows 2 strips, but it's better to make 3-4 ).

Shape mashed potatoes into a Christmas tree shape.

Wrap the cucumber strips around the potato, starting from the top.

It's going to look more like a Christmas tree if the cucumber is wrapped unevenly.

Slice off both sides of mini tomatoes, use to decorate your tree and it's done.