Why Are My Raspberry Leaves Turning Yellow Between the Veins?

Raspberry leaves that show yellowing between the veins while the veins themselves remain green — a pattern called interveinal chlorosis — are most commonly suffering from iron or manganese deficiency. The counterintuitive twist is that both minerals are usually present in garden soil in adequate quantities; the problem is usually that the soil pH is too high (alkaline), which locks these nutrients into a form the plant cannot absorb. Adding more fertiliser will not fix it — correcting the soil pH is the starting point.

How to confirm a pH problem

Test soil pH with an inexpensive test kit from any garden centre. Take samples from the top 15cm of soil in two or three places along the row. A pH above 7.0 is strongly associated with interveinal chlorosis in raspberries. A pH above 7.5 means nutrient uptake will be severely compromised regardless of soil fertility.

How to lower soil pH

Work sulphur chips or flowers of sulphur into the soil around the row. This is a slow process — the soil takes several months to a year to respond. Mulching with acidic materials (composted pine bark, pine needle mulch, ericaceous compost) and avoiding lime, wood ash or other alkaline materials helps maintain pH in the long term. A dilute solution of chelated iron or manganese (sequestered iron) applied as a liquid drench gives a faster temporary fix for severe deficiency while the longer-term pH correction takes effect.

Nitrogen deficiency — the other cause of general yellowing

Older leaves turning uniformly pale yellow (not interveinal) with younger leaves remaining green suggests nitrogen deficiency. Apply a nitrogen-rich feed or a balanced fertiliser in early spring when canes begin to grow. Yellowing that starts at the leaf margins in summer may indicate potassium deficiency, corrected with a potassium sulphate application.