Your gardening questions answered: What’s wrong with my raspberries?

I planted bare-root raspberries “Autumn Bliss” a few years ago. The first year all but one plant died. Thinking I had neglected them, I bought more bare-root plants and planted them in the same bed and these all lived. In their first year, they only produced a few raspberries, but last year they fruited well.

However, when I picked them they fell apart in my hand. I haven’t pruned them back yet, but they are starting to bud. Do you think they have a virus and what should I do?

Much as I love them, raspberries can be challenging to grow well, demanding a very fertile, humus-rich, deep, moist but (crucially) free-draining, acid to neutral soil to flourish. Unfortunately, they’re also particularly prone to infection by a wide variety of viruses passed on to the plants via a number of potential vectors, which include aphids, mites, soil-based eelworms and pruning tools as well as infected pollen. Symptoms of virus infection vary widely according to the particular virus, but classic signs include dieback, stunted growth, yellowing of leaves, blotching/mottling/puckering of the leaves and poor fruiting, including the exact problem you’ve described which is quaintly known as “crumbly fruit”.

Confusingly, however, there are also other non-viral causes for “crumbly fruit”. Those causes aren’t yet fully understood by scientists but seem to be down to a complex combination of the particular variety of raspberry (some varieties are more vulnerable than others) and the growing conditions that the plant faces during fruit formation. Anecdotal evidence suggests that the popular, late-fruiting variety “Autumn Bliss” is somewhat prone to this condition.

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To confuse matters even further, the fact that most of your first batch of plants died could simply be down to poor growing conditions such as a heavy, poorly drained soil, which raspberry plants hate. Or it could be down to the young canes being planted at the wrong time of year, leaving them vulnerable to a summer drought or extreme winter cold before their roots systems had a chance to properly establish. Or it could be due to any one of a variety of fungal diseases, to which raspberry plants are also prone.

Alternatively, it’s possible that the first batch of plants were infected and that this virus (or viruses) has now been transmitted to the second batch. All of which quite understandably probably leaves you even more confused as to what to do next.

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My suggestion is to give your existing plants one more shot, doing everything that you can in the meantime to create ideal growing conditions for them on the basis that this may hopefully resolve the problem. Along with an inability to tolerate poorly-drained soil, raspberry plants are sensitive to nutrient deficiencies, so after pruning them back hard this month, mulch your autumn-fruiting plants with a generous layer of garden compost or well-rotted manure (keep it out of direct contact with the canes) and sprinkle some pelleted organic chicken manure around the base of the canes. Some wood ash, if you have it, will also help with fruiting. Keep the plants well watered during any extended periods of drought and net them as the fruit starts to ripen to protect against birds.

But if the problem persists, then I’d advise digging out and carefully disposing of all the plants before replanting this autumn with new, certified virus-free canes in a different part of your garden or allotment. Newer, more vigorous and productive alternatives to Rubus “Autumn Bliss” include “Joan J”, “Polka” and (rather fittingly) “Caroline”.

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