Left to their own devices the canes can grow over ten feet in length.
I prefer to keep them a bit more manageable and improve the number of flowers produced.
Starting with the canes from last year.
In the spring coming out of their long winter nap you will look for when the growth buds on the canes begin to swell
Give them some time and you will be able to identify the growth points that have made it thru the winter and where you will prune off the parts of the canes that did not make it thru the winter.
Trim the canes back to just above the top most healthy cluster of leaves
This will allow the side canes to grow creating a more compact growth habit
Next to address the new canes that begin to grow this year.
I have the top wire of my trellis at 6 ft and so that is where I would like the growth topping out with out removing flower buds that are the fruit for later in the year.
At about 4 feet in height, you will pink out the growth tip of the cane. Do not worry about how much you remove of the growth tip all will be well.
This will result in the plant pushing it energy to the side buds below where you pinched out the growth tip of the cane.
These will develop into side branches
At the tips of these flower buds will develop. You can pinch out these side shoots to develop additional branches and flowers, but I prefer to limit the quantity of the berries forms so that they are the largest they can be,
Tie the developing branches to the trellis to keep them supported. As the fruit develops it will weigh down the cane and can cause the cane to rip off from the main stem.
The flowers will develop and bloom