Why are my tomatoes splitting?

Splitting is caused by uneven growth rate, which almost always traces back to inconsistent water. The skin sets at a certain size; if the flesh inside then expands faster than the skin can stretch, it tears.

The classic sequence is a dry period followed by heavy watering or rain. Under drought stress the fruit slows, the skin toughens, and then a sudden abundance of water causes rapid uptake that the toughened skin cannot accommodate. This is why splits often appear the day after a storm following a dry spell.

Consistency is therefore the whole fix. Water regularly rather than heavily and occasionally, and mulch the soil surface to buffer moisture and reduce evaporation. Container-grown plants are far more prone because their limited soil volume dries quickly, so they may need watering twice daily in hot weather.

Two patterns of splitting exist. Concentric rings around the stem end typically indicate rapid growth and are more common in some varieties. Radial splits running down from the stem are usually more serious and let in rot.

High temperature and humidity contribute independently, as does harvesting late, since fully ripe fruit left on the plant is most vulnerable. Picking at first blush and ripening indoors avoids much of the risk during unsettled weather.

Variety matters. Some cultivars, particularly large heirloom types, are inherently prone to cracking, while many modern varieties are bred for resistance.

Split fruit is safe to eat if used promptly and the split is clean and dry. Once a split begins to weep or shows mould, discard it, because the opening admits rot organisms quickly.

This is distinct from blossom end rot, which is a dark leathery patch at the base and relates to calcium uptake, itself usually a watering consistency problem too.