Every year, raspberries form robust buds at the base of annual branches, which are called basal buds. In the second year, strong annual branches are produced, which are called base branches. The growth of new shoots began to slow down, accelerated after the temperature rose, peaked in June, and then gradually slowed down. After harvesting, the two-year-old branches will grow again and stop growing after 9 months. After overwintering, the new branches of raspberries become biennial branches. They don't continue to grow, but only grow fruiting branches from axillary buds formed last year. After fruiting, the branches gradually dried up from top to bottom. In order to facilitate the growth of basic branches, biennial branches should be cut off along the surface after berries are harvested.

(2) flower bud differentiation

According to Tan Yu of Northeast Agricultural University's detailed research on the local main species raspberry for five consecutive years (1984- 1988), it is considered that in Harbin area, the buds on the basic branches of raspberry formed in that year were in the state of leaf buds before winter, sprouted in the spring of the following year, that is, in early May, and soon turned into the stage of flower bud morphological differentiation. The differentiation period of calyx primordium is mid-May, the stamen and pistil primordium is May 20th, the petal primordium is about May 20th, and the sexual organ formation period is from late May to early June. At the beginning of June, the sexual organs differentiated before flowering, and then the flowers opened.

The characteristics of raspberry flower bud differentiation are as follows:

1. The critical period of flower bud differentiation

Raspberry buds are in the stage of leaf bud differentiation from June to June. After the cold protection was lifted in the following spring, the bud was still in the state of leaf bud when it germinated in late April. At the beginning of May, the bud was elongated, and 2~3 young leaves grew obviously. When the petiole was about 10mm long, the number of nodes (leaves) of the bud had differentiated and began to enter the stage of flower bud differentiation. The topmost growing point is obviously enlarged, and one or several spherical inflorescence primordia are formed below it.

2. Flower bud differentiation sequence

The flower buds of red raspberry are mixed buds, and cymes can be produced at nodes 12~ 13. Inflorescence differentiation starts from the top and forms downwards in turn. Due to the concentration of flower bud differentiation in spring, especially the rapid differentiation of several inflorescences at the top, the floret differentiation among inflorescences is staggered at the same time. When the length of axillary bud is 1.8cm, the number of leaves can be distinguished by naked eyes, and then 1 inflorescence is differentiated. After 10d, the axillary bud is 3.6cm long, and the number of leaves can be distinguished 1 1, with 5 inflorescences. With the increase of temperature, the internode elongation is faster, the number of distinguishable leaves is basically stable, and the inflorescence differentiation speed is accelerated. Raspberry is a semi-shrub tree species, and the fruiting mother branch did not differentiate before the winter of that year, but the flower buds began to differentiate in the spring of the following year, which blossomed and bore fruit that year, and the fruiting mother branch withered in late autumn.

(3) Flowering and fruiting

Raspberry inflorescences are cymes, bisexual flowers, fruits are aggregate fruit, and there are as many as 90 drupes. The flowering period of raspberry in Harbin is in early June, with the first flower in the same inflorescence, and the flowering period is as long as 1 month. The fruit ripens in early July.