Rooting cuttings from a mature plant is one way growers and gardeners multiply their supply of many kinds of deciduous and evergreen perennials, shrubs and trees. Success is not always assured, however, so take more cuttings than you need. The best time to take cuttings from yews (Taxus spp.) is late fall to late winter. Cold temperatures prior to the taking of cuttings stimulates narrow-leaved evergreens such as yews to root faster.
Using a sharp knife or well-sharpened pruner, make 4-inch to 10-inch cuttings from the tips of the yew's branches. Choose stems that are about 1 year old, whose ends are hardwood or at least semi-hardwood. Snip or brush off the needles on the lower 2 inches of stem to prevent rotting. With the tip of a sharp knife, make a 1-inch vertical cut down each side of the base of the cutting, removing the bark. This promotes cell division and water absorption and removes hard tissue that may impede root formation.
Powders and gels containing hormones to encourage rooting aren't necessary, but they improve success rates and spur quicker rooting. Spread a small amount of rooting powder on a clean, flat surface and dip the base of the cutting into it. Don't re-use leftover rooting compound or add it back to the container in order to avoid contaminating your supply.
Use a sterile, quick-draining growing medium to deter bacteria and prevent rot. The most common mixture is one part sand, one part perlite and one part peat. Use a pencil or skewer to make a hole in the medium, insert the cutting and firm the medium around it. Water thoroughly, using a watering can with a fine rose.
Placing a clear cover over the rooting tray or a clear plastic bag loosely over individual pots sets up sufficient humidity so they don't dry out. To avoid mold, keep the medium moist but not wet and open the covers daily. Place the cuttings in a bright area but out of direct sun. Keep the temperature between 60 and 65 degrees Fahrenheit. You can use a heat mat, kept at 70 to 75 degrees, to encourage faster rooting.
A gentle tug on the top of the cutting will tell you if roots have formed, a process that may take only a few weeks or up to three months for yews. Transplant the cuttings into 4-inch pots of potting soil, covering with an open plastic bag for about a week, but gradually opening it wider to accustom the cuttings to lower humidity. Place them out of direct sunlight, extreme heat or cold.