Branch selection and shaping methods for Chinese ash (Fraxinus hupehensis) bonsai stumps

  Fraxinus hupehensis belongs to the Oleaceae family, genus Fraxinus. Native to Jingshan in western Hubei, it is a deciduous tree reaching over 30 m in height. Young and middle-aged trees have smooth, pale grayish-green bark, while middle-aged and old trees have vertical dark gray furrows. The new shoots that sprout in the first year should be handled according to the vigor of sprouting and branch growth of each stump.

  For vigorous trees, generally after the Beginning of Autumn in early August, when most branches have grown to over 40 cm, branch selection is carried out: keep the branches that match the intended shape direction, keep 1-2 branches from clustered shoots, and remove the rest. If a position that needs a branch has none, a surplus branch from the lower part of the trunk can be approach-grafted to the position lacking a branch, and the lower shaping parts should be pulled into place with rope or aluminum wire; at this time it is best not to use the wrapping method to tie and shape. Because Fraxinus hupehensis branches thicken quickly, if you are not careful the wire will cut in, affecting the beauty and growth of the primary branches. After branch selection, apply urea once every week at 10 g-20 g per sq m according to the planting area of the stump, to promote thickening of the new branches.

  Because Fraxinus hupehensis can grow when the average daily temperature is above 15°C, as long as new stumps have sufficient water, fertilizer and sunlight, the base diameter of vigorous branches can reach over 20 mm from the current year to before frost. Therefore, for terminal shoots, the tips should first be pinched to control length (for fast-shaped commercial stumps, the primary branches can be pruned and set, and the secondary branches pruned and set at the end of the year). Branches at the bottom and other parts that need thickening are left to grow freely. During management, observe at all times; if surplus shoots sprout from the base of branches on the trunk, they should be removed promptly, otherwise rampant shoots will shoot up suddenly, wasting nutrients for nothing and affecting the growth and thickening of the shaping branches.

  After frost causes leaf fall, the tree can be potted. Dig the stump material out of the sand bed, shake off the gravel from the roots, cut off overly long root fibers, prune and set the branch shape, plant according to the size of the stump shape, fill with nutrient soil; shallow pots should have a rim added so that fibrous roots do not show above the pot soil surface. Finally, water thoroughly and strengthen winter management. If the sand bed is not urgently needed for other use, you may prune branches in winter and pot it on the eve of spring sprouting, which is even better.

  For weak trees, although they sprout and send out branches, if the roots have not grown or have grown sparsely, they should continue to be cultivated in the sand bed, and potted only after the roots and branches grow vigorously in the second year. By all means avoid rushing to prune branches and pot them, which would affect the survival rate.