• erratic watering
• erratic temperatures

These 2 causes are often responsible for a whole range of problems with tomatoes: -

• Flower shedding
• Blossom end rot
• Immature fruit fall
• Split skins
• Sun scald
• Blotchy ripening
• Tomatoes not ripening

Of course temperature extremes is the most difficult of the 2 causes to manage as you are very much at the mercy of mother nature and what she throws at you, certainly where we are in the South of France, it is not unusual to see temperatures of up to 100F during the summer on occasion which will actually halt the ripening process.

If you have a greenhouse then you do have options for whitening the glass or opening doors and windows when the temperature is very warm, there are automatic window openers available that operate on a temperature basis to make this easier to manage, other than that you just have to do things manually.

Ideally you want to keep your temperatures constant and somewhere between 65F and 70F, the minimum temperature you can live with is about 55F and the maximum is around 90F. Out of doors this will be very difficult to control, so for cooler climates you may need a greenhouse and for warmer climates you can try temporary shading at the hottest part of the day or you can perhaps position them so that they don’t get full sun at the hottest part of the day, a little tricky because you still need sufficient sun to ripen the tomatoes i.e. at least 6 hours.

Watering is to a lesser extent affected by the weather but you do need to monitor whether there has been a lot of rain and whether you actually need to water that day, if the soil is moist and not dried out then you can probably  miss a watering session. It’s been said before but it is a fact that watering of tomatoes is extremely important they neither like to be dry or saturated and if you struggle to keep on top of your watering program then you may need to consider an automatic watering system.

* Top tip – extremes of moisture and temperature are compounded by the use of containers that are too small, the minimum size pot that should be used is 12″ diameter. The extra mass of compost slows the rate of temperature change and is less susceptible to drying out quickly.