Cut two willow tree branches to 16 feet in length. Select branches with a diameter of 1-1/2 to 2 inches.
Lay the two freshly cut willow branches' narrow sides together so that they overlap by 2 feet. Wrap heavy-duty floral wire around the branches 6 inches from the ends and every 6 inches in between. Twist the wire tightly so that the branches are securely connected.
Shape the branches into an arch. Measure the distance between the bottoms of the branches that form the arch.
Determine the location to erect your arch. Pound 24-inch metal stakes into the ground, using a rubber mallet. Place the stakes 4 feet apart. Leave 12 inches of the stake exposed above the soil.
Stand up your willow arch and tightly wire the base of the branches to the metal stakes. Keep the branches approximately an inch above the soil to prevent the willows from rooting in the soil.
Repeat these steps to form additional arches. Weave and wire additional pieces of willow branches between the arches for added support.