Blossom end rot

Blossom end rot image

Question ...

How often, and in what quantities, should outside tomatoes be watered? Mine are beginning to suffer from blossom end rot, which I believe is an indication that I've got the watering wrong.

Answer ...

Blossom end rot occurs when there are insufficient calcium levels in developing fruit. This is most common when the first trusses are forming and calcium demand is high. As water transports calcium around the tomato plant the condition is usually linked to inadequate or irregular watering. Tomatoes need the equivalent of 2-4cms rainfall every week, though the amount of water given is less important than maintaining consistent water levels. Watering daily, at least, will be necessary in hot conditions. As little as half-an-hour of water deficiency can cause the condition to develop. Pick off and compost any fruits that have been affected. Mulching around tomato plants with grass clippings, straw or hay will prevent plants drying out.
