Plant Doctor Archive

Diseased tomatoes

IN earlier issues of Weekend Gardener there have been items about growing tomatoes outdoors. But I grow mine hydroponically and get blossom end rot, especially in the fruit in the lower part of the plant. This year was the worst so far. Cucumbers were also a problem - only two or three when there is usually an abundance of fruit. I bought the nutrient mixture from the usual place and mixed it with the usual care and, of course, there's always an ample supply of water. Can you help?

BLOSSOM end rot in tomatoes can be caused by several different factors but it's usually a combination of two or more. For example, a simple lack of sufficient calcium in the nutrient solution can cause it.

However, there may be plenty of calcium but low temperatures or too high a level of other nutrients could cause an imbalance which results in the same problem.

As the problem on your tomatoes occurred mostly to fruit on the lower parts of the plant, I think low temperatures early in the season were most likely the culprit as it sounds as if the problem went away when the weather warmed up. Last spring and early summer the weather was unusually cool in many places with lots of rain and low light levels. Hopefully next season will be better.

Rather than make changes to the nutrient solution, which has worked well for you in the past, I suggest you watch the weather carefully next season and perhaps think about heating your greenhouse or even delay planting your tomatoes and cucumbers until the temperatures, both day and night, have warmed up.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.