For fruitnut (or other): potted blackberry question

lsohAugust 30, 2013

I planted 2 triple crown blackberry plants in spring 2012, each in a 14 gallon pot. Together, they produced 1 gallon of delicious, ripe, fresh blackberries. I don't know if that's a lot or a little for first year potted black berries, but we were pleased.

However, each plant has produced only one new cane this year. Surely we won't get many berries next year. Something's wrong.

Let me describe their care and feeding.
- I used an organic potting mix of mostly compost and pine bark fines. I have other fruits growing well in a similar mix.
- In 2012, I selected around 6 canes per plant, and tipped them at about 3'. Weaved them onto a small trellis. As I remember, I thought I tipped them pretty late, but I was waiting for the canes to grow a little first. Those canes (tipped in 2012) didn't produce much lateral growth until this year (2013). But they did grow a mess and produced a lot of berries.
- In 2013, I gave them a balanced slow release fertilizer at bud swell and again late June or early July.
- They generally get watered every day in the summer. In the winter the pots were in an unheated garage, but keep moist.

Any ideas about why these plants only produced one new cane? I'm thinking maybe
1) Not enough nitrogen?
2) Over cropped. Should have selected fewer canes in 2012 for 2013 production?
3) other?

Any suggestions for better results in the future?


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This was my second year with my TC plants growing in their new digs, like yours, in containers. I don't know what kind of plants you started with, but two of mine were rooted tips from the original plant I bought and that plant originally had only one short and narrow (less than a pencil) cane.

Each plant sent up at least one thick cane during the first real growing season (I think the original mother plant maybe had two).

From those three plants I harvested a gallon-sized plastic bag (freezer). Like you, I thought that was pretty good (and about the same as my boysenberries also in containers).

Going into Fall I have cut off all but the four strongest new canes on each plant. Considering the vigor of both kinds of berries I think that 4 canes is about as much as you can ask from containers. Those canes have been tipped at about 5 feet and I'll let any laterals that develop grow until the dormant season and then cut them back to about a foot.

My berries grow in tall cages (rectangular prisms), with one cane tied to each vertical edge. I feed weekly during the growing season with a liquid hydroponic mixture that I copied from some university site describing greenhouse production of containerized raspberries.

    Bookmark   August 30, 2013 at 6:49PM
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fruitnut Z7 4500ft SW TX

Only one cane sounds like not enough nitrogen. I fertilize a lot for container plants. If not they just don't grow. Everything else sounds great. One gallon is a great harvest so it can be very rewarding. I'm going to try another Black Diamond this winter but probably not in a pot. I'll plant in the ground in my greenhouse. That will likely provide more growth and fruit. Black Diamond is much less vigorous than Triple Crown.

    Bookmark   August 30, 2013 at 7:02PM
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What is your fertilizing schedule for fruits in pots?


    Bookmark   August 31, 2013 at 8:36AM
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fruitnut Z7 4500ft SW TX

No set schedule but a complete, controlled release once or twice a year according to directions. Then when wanting more growth add a soluable fertilizer once a week. The soluable could be 21-0-0 or Miricle grow complete fertilizer.

    Bookmark   August 31, 2013 at 9:24AM
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franktank232(z5 WI)

From my need to fertilize the heck out of container plants...i think its hard to over do it...especially if you are watering once a day.

    Bookmark   August 31, 2013 at 10:44AM
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    Bookmark   August 31, 2013 at 11:35AM
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shazaam(NC 7B)

I really like the soluble and controlled release fertilizer combination that fruitnut suggested. In previous years, I've relied on a soluble fertilizer alone, and my container fruits have never really thrived. This year, I added a light dose of Osmocote Plus in the spring and then applied a water soluble at 1/4 to 1/2 strength at ever watering. The difference was like night and day. I have a figs and raspberries that didn't get the CRF, and they're a fraction of the size of those that did.

    Bookmark   August 31, 2013 at 12:47PM
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