The green giant thuja remains in the public domain of plants, allowing anyone the right to propagate its cuttings. This majestic conifer grows upwards to 60 feet during its lifetime, making it a good specimen for wind breaks and privacy hedging. Thuja delivers quality cuttings in the winter after the tree reaches dormancy. Trying to propagate thuja cuttings during any other time of the year results in less than satisfactory results.
Take thuja cuttings from healthy trees to keep the spread of disease to a minimum. Make the cuttings about 6 to 8 inches long. Remove the bottom 4 inches of vegetation from the stem of the cuttings.
Fill the growing tray with potting soil. Create uniform holes in the soil with a pencil. The holes keep the rooting compound from rubbing off onto the surface of the soil. Dampen the surface of the soil, but keep it from getting soggy by misting with water.
Avoid contamination of the master supply of rooting compound by pouring 2 tablespoons of the compound into a separate dish. Dip the thuja cuttings into the rooting compound and stick them in the holes. Remove air pockets by tamping the soil around the plant cuttings. Air pockets breed bacteria, which kills cuttings.
Cover the growing tray with plastic and place it on the heat mat in a bright location, away from direct sunlight. Direct sunlight generates too much heat for the thuja cuttings to survive. The cuttings will wilt before they have a chance to root.
Ventilate the growing tray daily by removing the plastic for at least an hour a day. Check for mold growth and discard any infected or dead cuttings, so contamination does not spread through the entire tray.
Water only when the soil appears dry, and keep the water off the cuttings. Conifers suffer when water builds up on the foliage. Maintain care of the cuttings until new growth starts to appear. The new growth signifies a developing root system.
Remove the plastic when the roots develop, and move the growing tray into direct sunlight. Keep watering and maintaining the thuja cuttings until a healthy root system develops. Transplant into individual containers and continue growing until the desired size has been reached. Transfer the new thuja trees outdoors when weather permits.