The Japanese maple, Acer palmatum, is a deciduous broadleaf that reaches a height of 20 to 50 feet. The leaves vary in color from red to green depending on the specific variety. Japanese maple trees are popular as an ornamental feature due to attractive fall foliage colors that range from yellow to purple. Propagate the Japanese maple tree with softwood stem cuttings taken in late spring or semi-hardwood stem cuttings taken in mid-summer. The best time to take cuttings is during the cool morning hours to prevent moisture loss in the stems.
Remove an 8-inch softwood or semi-hardwood stem section from the current year growth on the Japanese maple branch by cutting it with a sharp knife. Softwood stems are new branch growth that are still green but snap when bent. Semi-hardwood stems are new branch growth that is mature and beginning to harden.
Prepare the Japanese maple propagation tray by filling it with a rooting medium made by mixing equal amounts of peat moss, perlite and course sand. Moisten the mixture with water and fill it into the propagation tray.
Cut off all leaves from the bottom 4 inches of stem. Pour a small amount of rooting hormone on a piece of waxed paper and dip the cut end of the Japanese maple stem into the hormone. Stick the stem into the propagation tray to a depth of 4 inches.
Mist the Japanese maple stems with water. Cover the propagation tray with a plastic bag to hold moisture around the stems. Set the tray in a warm location with a temperature of 68 to 70 degrees F and indirect sunlight.
Monitor the moisture level around the stems by opening the plastic cover each day. Mist the cuttings and rooting medium to prevent the soil from drying.
Pull on the softwood Japanese maple stems after three weeks of growth and semi-hardwood stems after six weeks of growth to see if they resist movement from root formation. Gently move the soil to verify the length of the roots.
Transplant the Japanese maple stems once the roots are a minimum of 1 inch in length. Plant the stems in 4-inch growing pots filled with a high-quality potting soil. Continue to grow the stems indoors for a minimum of one year and transplant them in an outdoor environment during the spring season.