Watering tips for tomatoes

Ever grown a nice crop of tomatoes only to have them spoil just before they were ready to pick? Splitting tomatoes and blossom end rot are frustrating disasters that can be avoided with these watering tips.

Why does it happen?

Splitting tomatoes is usually the result of uneven watering while fruit are forming. When soil moisture is low, the fruit develops, but the skin tightens. Then along comes a heavy rain event like a thunderstorm, which thoroughly soaks the ground, and the sudden moisture surge causes the fruit to burst.

Moisture stress can also cause blossom-end rot, a disorder that appears as a brown rot at the blossom end of the fruit. This is primarily due to a calcium deficiency, sometimes from low soil pH or calcium levels. More often, it’s caused by poor water supply. Since calcium is relatively immobile, inadequate moisture prevents tomato plants from absorbing the calcium they need.  

How to avoid

Naturally, the way to avoid these problems is to be diligent about watering, even if the plants don’t show signs of dryness, such as wilting. When conditions are warm give tomatoes a deep soaking every second day to ensure a quality harvest. It also makes sense to maintain a surface cover of compost, straw or sugarcane mulch to help hold moisture in the ground.

Something I like to do is bury a pipe next to the seedling when planting to direct moisture deeper into the soil, which saves lots of water. I use 40cm lengths of PVC or agricultural pipe, burying one end about 20cm deep. When plants are young, water the surface and fill the pipe. As they grow, water the surface less and fill the pipe more.

Phil Dudman has written about organic solutions for the top 12 tomato problems you need to watch for. You’ll find his article in our Spring 2025 issue (OG 160). Subscribe to the magazine and get practical solutions delivered to your door!