Boxwood (Buxus spp.) is a classic evergreen shrub valued for its dense foliage and suitability for hedges and topiary in many landscapes. Propagating boxwood from stem cuttings is the most reliable and effective method for cloning the plant, allowing gardeners to multiply specific cultivars and save money. This process involves taking semi-hardwood cuttings from the parent plant and providing a controlled, moist environment until new roots form. Following a few specific steps for material selection, preparation, and maintenance can lead to a high success rate in rooting these popular shrubs.
Selecting the Right Cutting Material and Timing
The optimal period for taking boxwood cuttings is from late summer through early winter (July through October), after the current season’s growth has begun to firm up. Cuttings taken during this window are considered semi-hardwood, meaning the wood is mature enough to survive but still young enough to produce roots. The material should be taken from healthy, disease-free stems that have slightly darkened or become woody at the base but retain soft, flexible growth at the tip.
Look for stems that measure approximately 4 to 6 inches in length before trimming. Taking cuttings early in the morning is beneficial because the stems are fully hydrated, reducing the chance of desiccation before planting. The ideal cutting will be from the vigorous outer growth of the shrub, ensuring the new plants will have a strong start.
Preparing the Cuttings for Propagation
Once the material is harvested, use a clean, sharp knife or bypass pruners to prepare the cutting, as dull tools can pinch and damage the stem tissue. The initial 4- to 6-inch stem should be trimmed down to a final length of about 3 to 4 inches. Next, remove the leaves from the lower half of the cutting, leaving only two to three sets of healthy foliage at the tip to reduce water loss.
To stimulate root growth, lightly scrape a thin layer of bark from one side of the bottom inch of the stem, a technique known as wounding. This abrasion exposes the cambium layer, which helps the cutting absorb rooting hormone and encourages the formation of new root cells. After wounding, dip the prepared end into a powdered or liquid rooting hormone, typically containing indole-3-butyric acid (IBA), and tap off any excess powder. Hormone application is not strictly required but significantly increases the speed and percentage of successful rooting.
Setting Up the Rooting Environment
The rooting medium should be sterile, low in fertility, and highly porous to ensure excellent drainage and aeration. A common and effective mix consists of equal parts peat moss, coarse sand, and/or perlite. This blend prevents the cuttings from sitting in saturated soil, which can lead to fungal diseases and stem rot.
Before planting, moisten the rooting medium thoroughly until it is evenly damp, letting any excess water drain completely. Use a pencil or a small dowel to create a hole for each cutting, preventing the rooting hormone from being rubbed off the stem during insertion. Stick the prepared cuttings into the medium about 1 to 2 inches deep, covering the area where the lower leaves were removed. Gently firm the medium around the base of each cutting to ensure full contact between the stem and the substrate.
Maintaining Cuttings Through the Rooting Phase
Successful rooting relies on maintaining high humidity around the cuttings to minimize moisture loss until roots develop. This is commonly achieved by covering the container with a clear plastic bag or a humidity dome to create a mini-greenhouse effect. Place the cuttings in a location that receives bright, indirect light, avoiding direct sunlight which can quickly overheat the enclosed environment.
The ideal temperature for rooting is cool to moderate, requiring protection from frost if propagating late in the season. Check the medium regularly, keeping it consistently moist but never soggy, and open the cover periodically to allow for air exchange and prevent disease buildup. Roots may begin to form in as little as one month, but the process can take up to three months or longer. To test for rooting, give the cutting a very gentle tug; resistance indicates that new roots have anchored the plant to the medium.