How often should I water tomatoes grown in containers on an unshaded rooftop?

Tomato    New York

I live in New York City and grow a variety of vegetables in containers on our rooftop. Because of the configuration of the buildings around us, during the summer the plants get unbroken direct sunlight from approximately 7 or 8 am until about 3:30 or 4pm, if not later. Conditions on the rooftop are also consistently windy. The windspeed isn't enough to damage plants (we had no wind-related damage at all last year), but definitely windy enough to influence how quickly our containers dry out.

I'm trying to determine how often I should be watering our tomatoes, as recommendations for watering container tomatoes seem to vary wildly. Some sites say approximately 1-2 inches per week, but that's proven to be completely inadequate, and other sites say I should be watering deeply once to twice daily, but I'm concerned that's going to be overkill. This past year we watered deeply (to the point of runoff) either daily or every other day and experienced significant cracking in most of our heirloom tomatoes (which wouldn't be explained by the particular varieties we grew), as well as sporadic blossom end rot. Because of the cracking and blossom end rot I suspect that I actually do need to be watering more, but I'm not sure. We also did not mulch last year and I'm wondering how much of a difference it will make if we mulch our pots this time around.


Posted by: Jacob Dean (1 point) Jacob Dean
Posted: March 1, 2019


Hi Jacob, watering tomatoes can be tricky. I do not have an exact answer for you but I can give you some tricks I have learned over the years! One of them is to make sure your container is large enough for each plant. A suggested size is a 5 gallon bucket per plant. Along with correct bucket size, ensure you have drainage at the bottom of the bucket. This can be done by putting small-medium sized rocks underneath the soil. You can also reuse other materials like Styrofoam to drain while containing the dirt. Another thing to keep in mind is that tomatoes prefer to be damp all day rather than wet. This can be done by watering light-heavy (depending on the expected temperature and humidity of the day) early morning and in the evening. If you are unsure whether the soil is damp, stick your finger in the soil up to 2 inches and if it is still moist than do not water it. I hope this helps! If you have any more questions feel free to ask, thank you for your question!


Posted by: Annalyse Kehs (1 point) Annalyse Kehs
Posted: April 10, 2019

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