The Green Giant Arborvitae, a fast-growing hybrid evergreen, is popular for creating dense privacy screens and hedges. This specific cultivar, a cross between Western Red Cedar and Japanese Arborvitae, must be propagated from cuttings to ensure the new plant retains the desirable characteristics of the parent tree. Propagating via this method allows gardeners to clone the exact genetic makeup of the hybrid, which is not possible with seed propagation. This guide details the process of successfully rooting Green Giant cuttings into new, healthy plants.
Timing and Necessary Supplies
The most successful time to take cuttings is during the late fall or early winter. This period corresponds to the semi-hardwood stage, where the current season’s growth has firmed up but is not yet fully hardened. Taking cuttings when the parent plant is semi-dormant reduces physiological stress and allows the cutting to focus energy on forming a protective callus.
To begin, gather all necessary equipment. You will need sharp, clean pruning shears or a knife, sterilized to prevent the spread of pathogens. A high-concentration rooting hormone, typically a powder or gel formulated for woody stems, will enhance success rates.
A suitable propagation medium must be sterile and well-draining, such as a 50/50 mixture of peat moss and perlite. This blend retains moisture while providing aeration to prevent rot. You will also need shallow propagation trays or small pots, along with a clear plastic humidity dome or sheet to cover the cuttings. These tools create the controlled environment necessary to keep the delicate cuttings from drying out.
Selecting and Preparing Cuttings
Selecting the correct material from the parent plant is crucial for successful propagation. Choose healthy, current-season growth that is firm and flexible, avoiding soft, limp, or fully woody material. The ideal cutting length is between six and eight inches, taken from the tips of side branches on a robust, disease-free plant.
For the highest success rate, employ the “heel” cutting technique by gently tearing the side branch downward from the main stem. This removes the cutting with a strip of older, semi-hardened wood attached to its base. The heel contains stored energy and cells that are more receptive to the rooting hormone. If tearing is not feasible, use the sterile knife to lightly scrape two thin vertical strips of bark away from the bottom inch of the stem to create a similar wounding effect.
Once harvested, remove the foliage from the bottom one-third to one-half of the stem. Stripping these lower needles prevents them from sitting submerged in the moist medium, which causes fungal disease and rot. The prepared base, including the heel or wounded area, is then immediately dipped into the rooting hormone. Gently tap the cutting to remove any excess powder or gel before planting.
Establishing Cuttings in the Medium
Before inserting the cuttings, thoroughly moisten the sterile peat and perlite mixture until it is evenly damp but not saturated. Pre-moistening prevents the dry material from wicking moisture away from the cutting and ensures the rooting hormone adheres to the stem. Use a pencil or small dowel to poke holes into the prepared medium, spaced so the cuttings do not touch one another.
Carefully insert the prepared cuttings into these holes, ensuring the lower half of the stem and the hormone-treated base are fully submerged. Gently firm the medium around each cutting to establish good contact with the rooting environment. Cover the propagation tray with the humidity dome or plastic sheet to trap moisture, creating a microclimate with near 100 percent humidity.
Place the covered cuttings in a location that receives bright, indirect light, avoiding direct sunlight which can scorch the foliage and overheat the dome. The ideal ambient temperature for root formation is moderately warm, maintained between 65 and 75°F. Lift the dome occasionally to allow for air exchange, which helps prevent the development of mold and mildew.
Long-Term Care and Transplanting
Rooting Green Giant Arborvitae cuttings requires patience, as initial root development typically takes between three and six months. During this period, the environment must be consistently monitored to maintain the balance of moisture and humidity. The medium should be kept evenly moist, but never soggy, to avoid suffocating the nascent roots and encouraging rot.
Watering is best accomplished by bottom-soaking the tray, allowing the medium to wick up moisture as needed, rather than overhead watering which can dislodge the cuttings. Check the moisture level regularly and mist the foliage lightly if the needles appear dry. Continue to ventilate the dome frequently to cycle the air, which reduces the risk of fungal infections.
After several months, check for root development by gently tugging on one cutting; slight resistance indicates roots have begun to anchor the plant. Once a robust root system has formed, the young plants must undergo hardening off before transplanting. This involves gradually acclimating them to lower humidity and normal atmospheric conditions over several weeks.
Begin hardening off by progressively removing the humidity dome for increasing lengths of time each day. Start with an hour and slowly increase the exposure until the cuttings can tolerate being uncovered all day and night without wilting. The new Green Giant trees can then be safely transplanted into larger nursery pots or directly into the landscape. Newly planted propagules require consistent watering until their root systems are fully established.