Raspberries are a unique berry fruit because they grow on canes, versus growing on established stems and limbs from the previous years. A cane is simply a fresh shoot that is sent up from either the root of the plant, or from a previous years’ growth.
First year canes that are sent up directly from the root of the plant are called primocanes, while second year canes that are sent up from the previous years’ growth are called floricanes. Both of these canes are capable of producing fruit.
Canes can be fragile, which is why trellising raspberry plants is highly encouraged. A cane can be broken under the weight of fruit, animal interaction, or wind. Once a cane is broken, that part of the plant will die and no further fruit can be produced. Trellising raspberry canes keeps them supported and up off the ground, making them less susceptible to breaking.