Diagnostic Case Study: No Raspberries

Question:

I was wondering why my raspberries have never produced. They get mostly afternoon sun, they seem to always have bees around pollinating, the canes themselves look robust and healthy... they were planted about 5 years ago and for the first 2 years never produced anything, not even flowers. The past few years they get flowers all over, but then they turn brown and never produce the actual fruit (the last photo is the closest I’ve gotten to a berry). The photos I attached from from 6/16, 6/28, and 7/16 respectively. Any ideas?

Plant Diagnostic Process

The Ask an Expert Master Gardener assigned to this question reached out to her fellow Master Gardener Volunteers for help in determining an answer. Several responded that there could be issues regarding pollination and a lack of pollinators, referencing Poor Pollination in Raspberries from UCANR, but it seemed strange that there would be zero pollination, especially three years in a row.

The Master Gardener reached out to university experts, who suggested the following:

Winter injury. Some winter-injured plants can bloom but don't set fruit.
A virus might contain pollen sterility. Symptoms would be apparent on other parts of the plant. Where did the plant come from?
Unlikely, but is there a severe nutrient imbalance?
How is the plant watered?
How much sun does the plant get?
How is the plant pruned?
Could they be growing blackberries (mistaken for raspberries), which are injured by late winter frosts?
To have nothing developed seems like plant hardiness, or repeated interference with pollination

Master Gardener Response to the Gardener:

Hello. I'm glad you've turned to AaEx.

Well this is a puzzle. I've consulted with the U of MN Extension raspberry expert, Emily Tepe, and we have a few questions for you because it seems to be more than a problem of pollination for several reasons.

What cultivars do you have and if there are more than one, are they all exhibiting the same issue?
Where did you get your raspberry plants?
What is your watering practice with these plants (i.e., how often and how much)?
Do you prune them and how and when do you prune them?
You do say they get afternoon sun but how many hours of sun is that (since the sun can move behind buildings and trees later in the afternoon)?
Are you seeing any other problematic symptoms on your plants?

Your answers may help us figure this out because even if there are fewer pollinators or there are barriers to pollination (e.g. rainy days), there would always be some fruit production even if sparse or disfigured berries.

Thank-you.

Gardener Follow-Up Answers

I can't remember off the top of my head, but I believe Heritage sounds familiar. I think at the time I had bought 3 plants and split them down the area and made 6, which have now taken over the garden bed. The entire patch produces flowers but no berries.
I purchased them at Gertens.
I watered by hand throughout the month of June since we didn't get much rain. I would water so the soil was sufficiently wet, esp when the flowers first appeared. I watered every other to every 3rd day until we started getting more rain. I haven't been watering in July because we have been getting a decent amount of rain.
Before the new canes come up, I cut out the old, dead canes and thin out the rest of the canes a bit to make room for new ones coming up.
The back of our house faces southwest. There is a big tree off to one side which tends to shade some of the raspberries on that end of the patch in the later afternoon. I'd say overall 6 hours of sun or so for the rest of the bed. I attached a picture of our backyard.
The canes and leaves all look healthy, up until this past week when the Japanese beetles have invaded... But the raspberry flowers were dead and shriveled long before they arrived.

Based on the provided picture, what do you think the issue could be?

The Final Answer from a Horticulture Educator:

I did some further reading and looked at the picture provided. Soil around foundations is usually very poor and raspberries are heavy feeders. The plants also appear to be overcrowded and restricted.

Because the plants bloom and it looks like they are starting to form fruit, but then don't develop, I am guessing the issue is nutrition and overcrowding.

Depending on her motivation level, she should at least be fertilizing these in the spring, working in compost when soil is workable and mulch. She should also be aware of overcrowding. If she is really motivated, she should start over and move these plants to a larger, truly full sun site (no tree shade), amend the soil deeply and spread those plants out more.

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