Post harvest black berry plant care?

Anybody recommend fertilizing post harvest for black berry plants? I have been pruning out the spent canes as the become evident, but didnt know if any fertilizer now would benefit growth for next years crop?

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Yes. Give them a potassium supplement. Since most supplements of K contain high concentrations, small quantities might be sufficient. Check the label.

The sooner the better as blackberries in many regions stop growing in October. Applying cow compost or similar in late winter and/or other fertilizers in Spring is a more typical routine.

I’d avoid that due to the N and P components. Sul-Po-Mag is a better choice for fruiting plants this time of year in your region.

As long as you give it what it needs, the plant will be ready to produce when time comes.

I have some friends that grow a lot of blackberries and all they use is cow manure amended into the soil. Those blackberries put out a large crop every year.

Not a bad choice for spring and early summer.

Can you explain?


The center of life for many plants (incl. blackberry) is below the ground in the roots – everything above ground is essentially solar panels and sex.

The volume and quality of harvest for an individual fruiting plant is usually determined by nutrient stores and protein development in the roots during the fall and winter months.

For your region, this is the wrong time to supply growth stimulation – in particular Nitrogen.

Protein and internal enzyme development is largely driven by potassium availability. A small quantity of potassium supplement at this time is typically beneficial. For most home gardeners, a 4-lb box of Sul-Po-Mag is sufficient for multiple years. Follow directions on the box or feel free to contact me with more details about your plantings for a dosage recommendation. Please note that more is not better - an extreme overdose will kill your plants.

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Why would you appose using nitrogen?

At this time in your region I recommend you don’t add any new fertilizer containing nitrogen because it will stimulate new vegetative growth.

I have been reading along with interest. Didnt want people to think I asked and didnt read the responses.


I agree. New growth at this time of year is much less likely to harden off sufficiently to develop full winter hardiness.