Detailed Explanation of Hokkaido Boxwood Cultivation Techniques

There are many propagation methods for Hokkaido boxwood. The following is a brief introduction to several commonly used methods:

1. Cutting method: The cutting method is further divided into hardwood and softwood cutting methods. Hardwood cuttings are carried out between October each year and the end of March of the following year. For units with sufficient seed sources, the cuttings can be cut slightly longer; for units lacking seed sources, the cuttings can be slightly shorter. The cuttings are 8 to 15 cm long, and the insertion depth is generally 3 to 5 cm. Roots can grow after 1 month. As long as cuttings are made according to the methods introduced below, seedlings with relatively good growth can be obtained quickly:

1) Lay out a sand bed with good drainage performance, and disinfect the sand bed with potassium permanganate or carbendazim two days in advance.

2) Prepare alcohol and plant rooting powder, and mix the solution according to the instructions.

3) When cutting the cuttings, do not choose shoots that are too tender. Those with a high degree of lignification are easier to root and sprout.

4) When pruning, keep the main trunk and cut the side branches, and leave at least one bud at the base to facilitate the next cut.

5) Remove the lower leaves of the cuttings, keep 2 to 3 leaves at the upper part, and after the cuttings are trimmed, soak them in rooting water.

6) Use a small shovel to make a furrow in the sand bed, place the cuttings at 5 to 10 cm intervals, and after placing them, cover with soil and press firmly. The row spacing is 10 to 20 cm.

7) The cutting process needs to maintain appropriate temperature and humidity. Watering should be based on temperature and humidity, and the leaves must always be kept moist. Do not water excessively, as this prolongs rooting time. After the seedlings root, watering can be appropriately reduced.

8) After cutting, roots generally form in about 30 days, and they can also be potted at the appropriate time. The nutrient soil for potting can be prepared with sand, soil, and peat soil each accounting for one third, to facilitate aeration. Do not fill the pots too full.

2. Single-bud cutting method: The single-bud cutting method can be used to rapidly propagate Hokkaido boxwood seedlings. Cutting is carried out between May and October. The bud piece is preferably 1 to 2 cm long, one bud with one leaf, and the leaf must be retained. The knife used to cut the buds must be very sharp, and after the bud piece is cut, it should be inserted promptly. Each square meter of cutting bed can hold 500 to 1,000 seedlings. Roots form 1 month after cutting, buds begin to sprout after 40 to 45 days, and after 2 months the seedlings can reach 10 to 15 cm in height.

3. Leaf cutting method: Select mature leaves as cuttings. The petiole of the leaf used for cutting must be complete. When taking the leaves, do not use scissors. It is best to twist the petiole off from the base of the bud by hand, and insert them as they are taken, or place the leaves in a basin of clean water. Storing leaves for too long will cause the cutting survival rate to decline. The insertion depth is 2 to 3 cm. After 20 days of cutting, callus tissue can form at the base of the petiole; after 30 days, new roots grow from the callus tissue; after 50 to 60 days, young buds form on the root primordium; after 70 to 80 days, the young buds break through the soil and grow into new plants. A 1 sq m cutting bed can hold 1,000 to 1,500 leaves, and the survival rate can reach more than 95%.

4. Seed sowing method: Hokkaido boxwood bears fruit early, has a large fruit set, and has a high seed germination rate. When the fruit skin cracks, it should be harvested promptly; otherwise, the mature seeds are easily eaten by birds. After the seeds are harvested, remove the red aril promptly. When removing the seed coat, use gentle force; if the force is too strong, the seeds are easily crushed. After the seeds are dried in the shade, store them with moist sand. The sand moisture must not be too high; high moisture makes the seeds prone to mildew and rot. The storage room temperature must not exceed 15°C. When the room temperature exceeds 15°C, the seeds are prone to germinate early. After the soil thaws, sow as early as possible. Sowing should be early rather than late. If sowing is late, the air temperature and soil temperature rise, the seeds root and sprout quickly, the seed roots grow long, and the seed roots are easily broken during sowing, causing damage to the seeds. Seedlings propagated from seeds show obvious variation, especially in leaf shape, which varies greatly. Among seedling plants, 50% to 60% of seedlings have leaves the same as the mother plant, 20% to 40% of seedlings have leaves that become pointed-leaf shaped, and 1% to 10% of seedlings have leaves that become broad and large. For seedlings propagated by seed sowing, regardless of how the leaf shape changes, the arborescent trait and fast-growth habit of the seedlings are almost the same as those of the mother plant. However, it should be noted that when propagating seedlings, do not easily throw away those pointed-leaf type seedlings.

5. Grafting method: Although Hokkaido boxwood shows an arborescent trait and grows 3 to 5 times faster than ordinary large-leaf boxwood, for Hokkaido boxwood to grow into large-specification seedlings with a diameter at breast height of 5 to 6 cm, it takes at least 6 to 8 years, or as many as 10 to 15 years or longer. To cultivate large-specification, large-quantity seedlings within 5 to 6 years, it is necessary to first cultivate Euonymus bungeanus used as rootstock. Euonymus bungeanus has a well-developed root system, a high transplant survival rate, and fast growth, and can be cultivated into seedlings with a diameter at breast height of 5 to 6 cm within 3 to 4 years. Hokkaido boxwood grafted onto Euonymus bungeanus rootstock forms a crown early, and the grafted seedlings have strong cold resistance.