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I'm an absolute beginner so bear with me.

I've started growing tomatoes but I'm seeing multiple problems:

  1. Looks like mushrooms are sprouting under the plant.
  2. The bottom of the fruit is black.
  3. The leaves at the bottom of the plant are curling.

Here is an array showing the (apparent) mushrooms, the black spots on the bottom of the tomatoes, the curling leaves, and then the overall planter.

Array of pictures showing the three symptoms, plus the planter

Based on looking around online I see that the mushrooms are likely caused by over-watering or too much moisture in the soil, and no opportunity for sunlight to hit the soil. But then item 2 (bottom of fruit is black) is most likely blossom end rot -- see the comments at the end of this post -- and the most likely cause of that is under-watering of the plant. Lastly, my research tells me that the curling leaves are a sign of distress, but there could be multiple causes of that distress.

I had been giving the plant a thorough watering 1x daily (I had no idea of the "correct" watering schedule, this was just a guess). I'm located in Southern California so the days have been very hot and dry lately. I've been giving plant food once every 2 weeks per the directions on the box. Am I over-watering? Under-watering? Or do I perhaps have both problems due to the small size of my planter? Any advice on the underlying problem, and best way to fix it, would be appreciated.

  • Two questions - is the planter open to the soil at the bottom, or does it have a bottom with drainage holes and is just sitting on the soil? And what soil did you use inside the planter? – Bamboo Sep 5 at 10:31
  • Daylength is rapidly decreasing now. Tomatoes notice that and become less vigorous. The shrooms make over-watering likely. End rot is sometimes encouraged by environmental stress, heat etc. I just trim generously around the stuff if I need a tomato. – Wayfaring Stranger Sep 5 at 15:51
  • @Bamboo the planter is just sitting on the soil (more like gravel). The bottom is solid wood and sits above the ground. But there are gaps between the slats of wood on the side of the planter, so I would suspect that drainage isn't a problem. Soil in the planter is Miracle Gro raised bed soil, mixed in with some older stuff that was in there before. – Mr. Snrub Sep 5 at 20:04
  • @WayfaringStranger so if I understand correctly, you're saying that the blossom end rot might be entirely beyond my control...? – Mr. Snrub Sep 5 at 20:05
  • That's been my experience re end rot, Mr. Snrub. As Bamboo says, consistent watering is important, but in my part of the US at least, weather is so variable, that you can get the rot no matter how careful, consistent, you are with the watering. Water here runs 180ppm Calcium, so that's not likely the trouble. – Wayfaring Stranger Sep 6 at 15:47
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As you suspected,the black parts on the fruits are blossom end rot - this is usually a result of erratic watering rather than simple underwatering. Once the fruits are forming, they need calcium - this is transported from the soil through the plant's vascular system and into the fruits. It is quite rare for the soil to be deficient in calcium, but if the watering is insufficient or irregular (maybe you forget one day and do it the next instead, or you usually water twice a day and only do it once for a day or so) then the calcium supply to the fruits is intermittent, and blossom end rot appears. In terms of watering, daily or twice daily in hot weather is probably essential, but generally, feel the top of the soil with a finger - if it feels just about dry, water, if its still wet, don't. Water should always be applied to the soil and roots, not the foliage, to discourage disease.

The toadstools are nothing to worry about - the mycelium for these will have been present in the soil already, and these are just the fruiting bodies and should disappear shortly. If you have been overwatering, that would have encouraged them to form, but they are not uncommon at this time of year.

The container is too shallow, as you also suspected, which is the likely cause of the stress symptom on the foliage - tomatoes should be in a container that is at least 8 inches deep and 6 inches wide, but bigger if possible. Given there is no proper drainage at the bottom, it's possible the soil remained wet for too long, but as the roots grew and took up all the space in the container, it would have been more difficult to keep the plant well supplied with water because of the shallowness of the soil within. You might well have watered thoroughly in the morning or evening, but as the plant matured, it was probably necessary to water twice a day - this difficulty in keeping the plant regularly hydrated would link in with the presence of blossom end rot. If the plant is still growing and producing fruit, then check the soil for dryness morning and evening, to try keep it evenly hydrated. Next year, use a much deeper container...

You can still eat the fruits with the blossom end rot - just remove the rotted parts first.

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  • Excellent and thank you. I was wondering if it could help to re-pot the plant in a bigger container, but based on your comment "Next year use a much deeper container" I'm guessing that re-potting would not be a viable option here...? – Mr. Snrub Sep 6 at 2:36
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    Unfortunately, the roots by now will have formed more or less the same shape as the container, which would make it next to impossible to move into something deeper and not so wide without causing root damage. Unless you're trying to keep your tomato going over winter, its coming to the end of its time anyway,although I don't know how long the growing season is where you live. You are likely to lose some of the topgrowth and fruits if you repot now.,.. – Bamboo Sep 6 at 9:38

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