Hi, I have been away for three weeks and when I got home found my spinach and silverbeet have gone to seed. One of the spinach plants has a really thick flattened stem. What is wrong with it? Thanks, Owen.

The thick, flattened stem is called fasciation - the flattening of the cells in the growing tips of the plant. This can be genetic, or it can be fungal, bacterial, viral or caused by insect damage on growing tips. It is also caused by changes in temperature, zinc deficiency, excessive nitrogen in the soil or dry periods followed by excessive rain or watering.

Because you've been away for three weeks it is likely your plant's weird stem has been caused either by temperature fluctuations, insect damage or inconsistent watering. Recommend you remove the plant as it has gone to seed, however don't be concerned as fasciation is mostly a physiological disorder so there is little chance of it spreading to other plants.