Why are the leaves on my tomato plant turning yellow?

Tomatoes are rewarding crops, but thanks to this year’s heatwaves (I’m defending my tomato care skills at all costs), the leaves on my tomato plants are yellowing more than they usually would.

Learning how to grow tomatoes isn’t that difficult once you know how to water, feed and support them properly, but this summer’s heatwaves have taken some of their fate out of our control in recent weeks.

If you’ve found yourself wondering why the leaves on your tomato plant are turning yellow, there are four likely culprits.