Thank you for contacting the Jeffco Extension Garden Help Desk with your question regarding  your raspberry and blackberry bushes.  

Here are the fact sheets that we have available for raspberry and blackberry bushes.

Growing Raspberries in Colorado Gardens

Growing Blackberries in Colorado Gardens

There are fall-bearing and summer-bearing berries.  Knowing which type you have will determine the best time to prune and fertilize your plants.

In the documents linked above, it details how pruning can significantly impact plant performance.  

Both blackberry and raspberry bushes prefer well-drained soil.  Heavy/clayey soils may result in poor performance regardless of fertilization.  There is a paragraph about what makes raspberries produce poorly in this document https://planttalk.colostate.edu/topics/fruits/1219-diagnosing-raspberry-problems/#:~:text=There%20are%20several%20factors%20that,their%20second%20year%20of%20existence.

It was a good idea to prune surrounding plants to give the berry bushes more sunlight as they do prefer more sun.

 To have a better idea of the chemical composition of your soil, you could purchase a Horticultural Soil Test through the Colorado State University Soil Testing Lab.  There is information at this link.   https://agsci.colostate.edu/soiltestinglab/    If you pursue getting your soil tested and want the tester to send you fertilizer recommendations, include the depth of the soil that you included with your sample and add a note that you would like fertilizer recommendations.

Note that the The Espoma Soil Acidifer you mentioned contains Ammonium Sulfate and not Aluminum Sulfate.  Always be sure to follow the package directions on soil amendments carefully and wear appropriate personal protection as directed.

As for growing grapes, there are a couple varieties that are recommended in Plant Talk: Grapes:   "Along the Front Range, grape varieties such as Concord, Perlett and Beta are successful. Concord Seedless is a mediated fruit producer with medium vine vigor and high winter hardiness. Perlett is a European variety producing white, early season fruit. Beta fruit ripens very dark colored in September and can be used for making juice or wine."

Grapes require full sun, good drainage and support for the vines.  It sounds like the fence would provide adequate support, but you'll need to determine if the plants will get sun at the beginning of the season at the base to encourage young growth.  As the plants get taller, will they 'reach' the sun available later in the season?  

If you have further questions, please contact us again.

Sincerely,

Sue

Master Gardener Help Desk, Horticulture

Colorado State University Extension, Jefferson County

jeffcoextension.org

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303.271.6632 - Direct

303.271.6620 - Office

15200 West 6th Ave, Unit C

Golden, CO 80401

CSU Extension programs are available to all without discrimination.

I've planted some rasberries and a few black berry varieties in my (small) back yard almost 5 years ago. After the first few years of no blossoms/berries, I assumed they weren't getting enough sun due to nearby shrubs/small trees. I cut them back so more than 6+ hours of direct sunshine. After a year or two, still no blooms. They've spread (rhysomes) quiet a bit, so they seem to be healthy. I'ver fertilized, still nothing. I was about to rip them out and when as a Colorado Master Gardener I did some research and one thing suggested was the soil ph. Knowing Colorado soils are alkaline, I thought this could be the reason (though our county CMG office raises rasberries). So I thought I try to lower the ph using aluminum sulphate using a product called "Espoma Organic Soil acidifier soil amendment. I bought a 6lb bag and pour about a cup of granules at the base of most plants to see if I could get blooms. Probably too late. . this year? So I'm going to buy a bigger bag and spread over this 8x8' area, and if that doesn't get a change, maybe cut them back in the fall and see if I can work this product more "into" the soil with a small tinged rake, and hope for the best. . next year. Since my back yard planting ares (no grass)is VERY small ~50'x20', if they don't bloom next spring, I'll rip them out to provide more space for my perennial plants.

I would like some advise if this is a good idea or is their a better course to follow. I'm not a veggie gardener, more of a blooming gardener. I want to plant seedless grapes along my 6' fence that I've mounted a trellis but it faces north and during high sun summer, the sun doesn't quite reach the bottom of the fence. Should I abandoned this idea too?

Appreciate some advice. Neither is critical to my ambitions, but would be nice to have som "produce" from my labor.