Successfully growing plants from cuttings depends on getting the cutting into the growing medium quickly and keeping it moist while it takes root. Do not fertilize before taking a cutting. Fertilizer encourages the growth of foliage, and rooting requires the plant to put all of its energy into growing roots. Mother plants grown with hydroponic nutrient solution need to be purged from the nutrients by watering with nothing but water for three or four days before taking the cutting.
Some plants will grow a new plant from part of a leaf or a small piece of a stem; others need a stem with several leaves and nodes or parts of a branch or vine. Consult a propagation chart to determine which kind of cutting is best for your plant.
Herbaceous cuttings taken from a 3- to 5-inch piece of stem with all but the uppermost leaves removed will usually root quickly.
Cut softwood cuttings from soft new growth that has sets of older and newer leaves. Take these cuttings in early summer and take care to prevent them from drying out.
Cut semi-hardwood cuttings from the current year's growth in mid-summer through fall. Take hardwood cuttings from dormant wood.
Rooting hormone is usually not necessary; most plants will root successfully without it. Harder-to-root plants are helped along by dipping the rooting end into rooting hormone before placing it in the rooting medium. Poke a hole in the rooting medium to avoid rubbing off the hormone; place the stem in the hole, then firm the medium around the stem.
Builders sand, normally used in mixing concrete and filling sandboxes, is available at the hardware store or builder supply. It is free of salts that can harm the plants and makes a good rooting medium. Sand supports the stem while being loose enough to allow the roots to grow. Moisten clean sand before use and keep it moist during the rooting process.
Commercial rooting blocks are also available; some have natural rooting hormones incorporated in the block. These do a good job of supporting the plant, but are more expensive than sand.
Taking the Cutting
Prepare the rooting medium in advance. Moisten the sand and place it in a pot or cup, ready to receive the cutting. Make up the rooting hormone, if required, according to the package directions.
Make the cut with a craft knife or razor blade. Make a clean cut without crushing the stem. Remove lower leaves and place the cutting immediately into the growing medium.
High humidity is vital to the success of rooting plant cuttings. When rooting only a few plants mist the plants with water and cover with plastic to maintain humidity. Keep the cuttings humid enough that small water droplets condense on the plastic. The plants must absorb moisture from the air since they do not have roots yet.
Growing trays with clear plastic domes are commercially available and provide a mini-greenhouse-type environment. When rooting a large number of plants, an automatic mister maintains humidity. Other options are to use a humidifier next to the cuttings, or place the pots with cuttings on a tray of rocks sitting in water.