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I bought a young blackberry vine in the spring 2 years ago and planted it in my "balcony garden" (57cm wide, about 3m long and 25-28cm deep soil). I don't remember the type or other details about the plant, only that it's a common variety here in Austria.

The vines grow very well and there are a lot of them, making a thick bush, that I sometimes have to trim. However, the plant hasn't flowered at all. Not a single flower and obviously no fruit.

I don't use pesticides. All our other plants grow well in the same garden: wild strawberries, tomatoes, thyme, 2 types of lettuce, rose and some other herbs. The soil is slightly acidic, nutritious and a bit loose.

The issues (pests and viruses) I could find would only reduce the amount of flowers and/or produce inedible or low quality fruit, but nothing that would cause no flowering at all.

Thank you in advance for any tips.

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    What kind of pruning did you do? Selected canes or more like overall trimming?
    – Stephie
    Commented Jul 25, 2022 at 9:12
  • Overall trimming of too long vines and I cut away vines above the base when it gets too thick. I usually choose those that look a bit worse.
    – Sjama
    Commented Jul 25, 2022 at 10:45
  • Does your soil have enough calcium, potassium, phosphorus, and nitrogen? Commented Jul 26, 2022 at 9:31
  • I use natural fertilizer and egg shells. Calcium definitely enough. If any other nutrient was lacking, wouldn't my other plants have issues as well?
    – Sjama
    Commented Jul 27, 2022 at 8:42

1 Answer 1

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Blackberry vines are usually very long, often 2m or more, unless you have a compact variety, which the length of your vines (3m) truly not indicates.

The first issue to consider is the size of the container. This source suggest the roots are 30cm deep and 60cm in width. You have "a lot of" vines in a limited container. First change to try is pruning. The latter source suggest keeping 16 canes per plant every year. If your container is smaller than 30cm x 60cm x 60cm then you should keep less than 16 canes proportional to the container size. Also consider to limit the length of the canes in the spring. Alternatively you can change to a compact variety with might be much easier to handle in a balcony garden.

Next issue is understanding the canes: Even the root system is perennial the canes are biennial. First year canes are called primocanes and canes from last year are called floricanes, and unless your variety is flowering on primocanes, then you should expect flowers on the floricanes. After harvesting the last berries on a floricane you must prune it at the base. It may survive to a third year, but most likely you will not see any flowers the third year.

If your variety is flowering on primocanes, then you can prune all canes to the base in the autumn. Else it important to keep exactly the primocanes to the next year as they then will become floricanes.

In late spring the floricanes will grow branches, and you will see flowers on those branches only like on this photo:

Flowering Branch

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