
Yellowing leaves are a tell-tale sign of a nutrient deficiency
Having looked back at some photos of my Polka raspberries from last year, I think they have been suffering from a nitrogen deficiency. Not surprising, since I barely remembered to water, let alone feed, the raspberry canes all year. The tell-tale yellowing leaves didn’t have much of a trace of brown in them, which would suggest a magnesium deficiency. Rather, the pinkish hue that crept into some of the leaves made me pin the lacklustre foliage and yields on a lack of nitrogen.
Usually, I start the year off by dressing the ground around the shallow raspberry roots with some compost, followed on with fresh grass clippings to release nutrients and retain water. Having failed to do either last year, this year I need a quick fix (poultry poop, free range from friends’ pet-only homes), followed by a liberal mulching of well-rotted garden compost for a slower-release supply of nitrogen.

The raspberries looked a little healthier, but still weak, earlier in the season
If there’s a magnesium deficiency there, half a cup of Epsom salts diluted in a watering can should do the trick.
I’m keeping my fingers crossed that a little bit of TLC and a boost in the right nutrients will be just the fix I’m looking for, especially as my mum is ready and waiting in the wings to collect lots of the fruit for her cake baking this year. That’s more than enough motivation in itself to get the plants back in working order!
The trick to tell the difference between calcium and magnesium deficiency is that Magnesium is Mobile. So the plant will move it if it can to the newer leaves, leaving the older leaves to yellow. Calcium deficiency looks the same but in the newer leaves. These photos look more like magnesium deficiency.