Source:
http://figs4fun.com/Rooting_Bag.html
ROOTING CUTTINGS IN A BAG
Take dormant cuttings approximately 8" long, and wrap in very slightly damp paper towel or newspaper, covering the entire cutting except the bottom 1/2". This allows the bottom end to "callus", which helps to prevent rot, when rooting. If you are doing several cuttings, roll the first one in the damp paper, then add one, and roll, and add, and roll, until you have 5-6 cuttings in a bundle. Place the bundle(s) in a sealable plastic bag (a Ziploc or zipper-bag works well). Place in a warm place, with a temp of 70-80 degrees F (not in the sun or next to a heat source which considerably hotter than the desired temperature). Check frequently for signs of mold, and air out the cuttings is necessary for a few hours. Re-moisten the paper if necessary (a spray bottle works well for adding water, though this is not usually needed if the bag is tightly sealed). Under the conditions of warmth and humidity, roots will develop, starting as small white "bumps" called initials, and gradually growing into longer roots.
When there is good development of roots and/or initials, unwrap carefully, and pot up as follows. Use clear plastic picnic glasses, of about 45 ounce capacity. Drill or poke 4-5 drain holes in the bottom. Stacking 3-4 cups together makes them stiffer and easier to make the holes. Place about 1/2' coarse, well-wetted Vermiculite in the bottom of the cup, insert the cutting, and fill the cup with coarse, well-wetted Vermiculite. Place the cuttings in a container (I use a plastic storage box), with a wire rack or other suitable arrangement, which will allow the water to drain through the cup and keep the cup from standing in any water. Return the cuttings to your warm place. To maintain humidity, you will need to cover the container to simulate a greenhouse environment, but leaving it open for fresh air, periodically, to avoid mold. Water as necessary. The higher humidity environment requires much less frequent watering, which yields better moisture control in the root zone and leads to less rotting of the cuttings.
The most important element is providing overall humidity, without keeping the root zone overly wet.
The coarseness of the Vermiculite allows air in the root zone, and holds moisture in the root zone. If the Vermiculite is too fine, or packed down too much, it excludes air and holds too much moisture in the root zone. Generally, in a warm environment, if there is condensation on the inside of the cup, there is sufficient moisture, if not, it is too dry. The clear cup makes monitoring root zone moisture much easier.
The clear cup is important, enabling you to monitor of root development visually. Leaf development is absolutely NOT an indicator of root development.
When there is good root development (do not rush this step, or be in a hurry to repot in potting soil) repot in a one gallon pot using a minimum of 60% Perlite in the mix, and the other 40% compost or similar organic component. The vermiculite will shake out of the cup, when pointed down at about a 30 degree angle and rotated and squeezed, followed by the rooted cutting. After potting, place in very, filtered shade, with good humidity until the plant has adjusted and is stable; then increase sunlight gradually. Water when necessary. After about a month, water, and let the plant absorb the water for 1 hour, followed by "watering" with a one half strength solution of Miracle Gro. This keeps you from "burning" the plant with the fertilizer. Fertilize twice a month. When roots begin to grow out the 1 gallon pot (roots growing out of the drain holes), repot in a 2 gallon, with 40% Perlite and 60% Compost. When roots begin to emerge from the drain holes, move to a 5 gallon pot, using 100% compost. When roots are visible in the drain holes of the 5 gallon pot, plant it in the ground. At this point, the plant is sufficiently developed to be stable and durable. Many cuttings will grow to 2-5' tall in their first year, but some varieties are slower growing.
If you observe the principles, you can also root larger, thicker cuttings, as well.