One of the few conifers which can tolerate household conditions, the Norfolk pine (Araucaria heterophylla) reaches heights of up to 200 feet in the wild. It remains smaller indoors, often serving as a potted holiday tree during the Christmas season. Perennial in U.S. Department of Agriculture plant hardiness zones 10 through 11, it usually is grown as a houseplant. You can propagate the tree most easily from seeds or air-layering. Cuttings are more problematic.
The seeds of Norfolk pine usually mature between mid-summer and autumn inside the 3 to 5-inch spherical female cones of a tree ten years old or older. Break those cones apart to harvest the teardrop-shaped seeds, which are enclosed in wedge-shaped scales. For the best germination, plant those seeds as soon as possible after you harvest them. If you must store them, dry them on paper towels or newspapers for 1 to 3 weeks before storing them in a capped jar inside your refrigerator. The University of Hawaii Cooperative Extension Service warns that the seeds' viability will decline by 50 percent every three months.
You can plant the seeds outdoors in a partially shaded raised bed -- in areas where the tree is hardy -- or in a pot with drainage holes, either of which should be at least 12 inches deep. Fill the bed or pot with a mix of one part loam or potting soil, one part sand, and one part peat. Push the point of each seed at a 45-degree angle into the surface of the soil, leaving its broader end protruding from the soil.
If you use a pot, place it under the end of a grow-light or on a partially shaded windowsill, at a temperature between 60 and 90 degrees. Either in a bed or pot, seeds whose soil is kept damp should germinate rather erratically over a time span ranging from 4 days to 6 months, with the majority sprouting by the 12th day.
Norfolk pines may become leggy when grown in low-light conditions indoors and eventually will outgrow their allotted indoor space due to their size. To restore a plant to its original less lanky condition and reduce its size, Tim Johnson, director of horticulture for the Chicago Botanic Garden, suggests that you root the upper part of the tree while it still remains attached to its original roots, in a process called air layering.
Find a bare spot on the tree's stem 12 to 18 inches below its tip. After cleaning the blade of a sharp knife with rubbing alcohol, slice upward into that bare space for about 1 inch, only penetrating about halfway into the stem. Wedge a toothpick into the cut to prop it barely open.
Soak the cut with a liquid rooting solution of 1 part liquid rooting concentrate and 4 parts of water or whatever amount is indicated for hardwood cuttings. Pack damp sphagnum moss around the cut, tie it in place with string, and enclose the moss in plastic wrap, taping the wrap firmly to the pine's stem above and below the cut to keep the moss damp. After about 1 month, roots should begin to appear. Once they have thoroughly pervaded the moss, you can remove the plastic wrap. After cleaning the blades of your pruning shears, as you did the knife, cut the stem below the roots, and pot up the new little tree.
Starting cuttings from Norfolk pine can be tricky, as each one should be taken from the topmost tip of a young tree -- preferably a seedling -- if that cutting is to root well and grow correctly. However, such pruning will ruin the shape of the seedling from which you take the cutting. As Lynn Hunt warns in the Christian Science Monitor, "If you prune a tip or healthy branch, new growth will go upward, not outward." Also, seedling cuttings can take up to 3 months to root, while cuttings from older trees may require an even longer time.
If you want to try a cutting anyway, snip off the topmost 6 to 8 inches of the central leader and remove all of the foliage one-third of the way up from its base. After filling a pot with a moist mix of 1 part peat and 1 part perlite, dip the bare base of the cutting in a solution made from combining 1 part of rooting concentrate and 19 parts of water -- or the amount recommended for softwood cuttings -- and insert that base into the potting mix. Repeat this process as necessary for more cuttings. After placing a few short stakes around the outer edge of the pot, encase it in a large plastic bag with the stakes holding the plastic away from the cutting or cuttings.
Tie the bag shut with a twist tie, and place the pot in a warm position where it receives bright indirect light, until new growth indicates that the cutting or cuttings have rooted. At that point, begin to remove the bag from the pot for a short time period each day, gradually lengthening that period until the bag is off permanently.