What types can the buds of walnut trees be divided into?

  Walnut is a monoecious plant with separate male and female flowers, and its buds can be divided into leaf buds, female flower buds, male flower buds and dormant buds.

  Female flower bud (mixed bud): mostly borne on the first 1-3 nodes at the tip of the branch. Its morphological characteristics are: the bud body is the largest, spherical, with scales tightly wrapped, and the bud tip is bluntly rounded. After the female flower bud germinates, it first puts out a fruiting shoot, and then bears 1-3 or more female flowers at the tip of the fruiting shoot, and flowers and fruits. In precocious walnuts, the mixed buds are not only borne at the tip of 1-year-old branches, but lateral buds may also be mixed flower buds, generally 2-5, and at most more than 20; in late-bearing walnuts, they are mostly borne at the tip of 1-year-old branches or on the 1-2 buds below it, solitary or overlapping with leaf buds and male flower buds in the leaf axils. After germination, they put out fruiting shoots, and at the tip of the fruiting shoot, female inflorescences are borne, flower and fruit.

  Male flower bud: generally borne on the 2nd to 10th nodes below the terminal bud of the branch, the bud body is long elliptical, and the scales are very small and cannot cover the bud body, so it is also called a naked bud. The male flower bud is a pure flower bud; after germination it only puts out male flowers, in the form of catkins, and does not produce branches or leaves. Longer male inflorescences can reach more than 12 cm in length, have more than 10 male flowers, and produce a large amount of pale yellow pollen.

  Leaf bud: also called vegetative bud. Mostly borne at the tip of the branch or below the mixed buds of the fruiting shoot, and leaf buds may be borne at every node of the branch. The bud body of the terminal leaf bud is larger, while the bud body of the lateral leaf bud is smaller; after the leaf bud germinates, it puts out a vegetative shoot. The leaf buds located on the upper part of the branch, when nutritional conditions are good, can put out plump and robust new shoots and can transform into fruiting mother branches. The smaller leaf buds in the middle and lower parts of the branch mostly do not germinate and remain in a dormant state. In this way, the branching situation of the vegetative shoot of the walnut tree is that the terminal bud produces a long branch, below it short branches are produced, and the middle and lower parts form a bare zone; after many years of growth, this causes the branch position to rise and the fruiting position to move outward.

  Latent bud, that is, dormant bud. It is a type of leaf bud. It is mostly borne at the base of the branch, with a small, round bud body, generally does not germinate, and its vitality can be maintained for from several decades to more than a hundred years; as the trunk and branches thicken, it is gradually buried into the bark, and when stimulated, it can germinate and put out shoots, and is used for renewal and rejuvenation.

  The nature of the terminal bud of walnut differs depending on tree age. After the terminal bud of a young tree germinates, the growth amount is large, forming scaffold branches and constituting the trunk. After entering the fruiting stage, most terminal buds form mixed buds, which can put out branches and extend growth, while a few terminal buds still continue to put out branches and fruit, expanding the crown. The terminal buds of walnut are divided into true and false; those that do not bear female flowers have true terminal buds; those whose branch tips bear female flowers cannot continue to put out branches and grow after fruiting, and their terminal buds are called false terminal buds. The false terminal bud is formed by the elongation of the base of the first lateral bud below the female flower bud; the true terminal bud more easily forms a mixed bud, and its fruit-setting rate is also higher.

  The compound buds of walnut are borne in the leaf axils of branches, arranged one above the other, also called vertical arrangement; the upper bud is the main bud, and the lower bud is the secondary bud. Their arrangement is most commonly leaf bud, male flower bud and two overlapping male flower buds.