Problems w/ tomato starts

Asked April 28, 2018, 6:19 PM EDT

My tomatoes, started from seed, were growing just fine but recently have developed a problem. The underneath sides of the leaves are turning purple, then they shrivel and the plant begins to die. The attached photos show (1) leaves in the early stages, (2) a seed leave affected, and (3) shriveling leaves. (3) also shows shriveled branches hanging from the main stem. The growing medium is a mixture of commercial potting soil, peat moss, vermiculite, and a small amount of fertilizer. The fertilizer is a mixture of calcium, cottonseed meal, bone meal, and kelp meal. Plants receive about 14 hours of artificial light per day. I have used these same techniques in past years with good results. Any recommendations would be appreciated

Lane County Oregon

8 Responses

Thank you for including images with your inquiry. I also appreciate the numerous details you’ve included about the plants and their care. It’s certainly distressing when things go awry after years of success. I’ll add a few comments then perhaps we can resolve this together.

The purpling of the leaf reverse is commonly caused by lack of phosphorus in the plant. That occurs if temperatures are low (below 55F) and/or if phosphorus is in short supply in the growing media.

Although your growing mix sounds as if it should work for seedlings, the organic fertilizers may be available at too low a rate because the soil organisms required for their use by the plants are missing.

If your goal is to use only organics, liquid fish may work better for now. If your choice is flexible, consider using a liquid synthetic fertilizer until the plants go into the garden.

The seed leaves often fail early in the process if a brief environmental glitch occurred. More often than not, it’s related to a brief water shortage.

The 3rd image is possibly related to an exposure to cold and/or to higher than normal humidity, the latter most likely coupled with low air circulation.

The background in the first image suggests the plants are indoors. If so, how close to the window are they?

Further, because the plants are leggy – a bit spindly – what kind of artificial lights are you using? Whatever they are, can you move them closer to the plants?

Thanks for your response. I will try the liquid fertilizer.

In regards to your other observations and questions:
Plants are in an insulated outbuilding. A space heater maintains a minimum temperature in the low 60's. During the day, the temperature rises to the low 70's. RH varies between 60-80% as the temperature varies. Plants are watered a small amount daily to avoid saturating the soil. No run-off has been observed. The building has two large South facing windows. The plants are on tables immediately adjaent to these windows. Artificial light is supplied by banks of 5000K color temperature compact florescent bulbs on 6" centers. These are height adjustable and are kept 2-3" above the plant tops. It is likely there is little air movement since the building is unoccupied. I could add a fan if you think that would help. My plants have always been on the spindly side for some reason. They always seem to improve after transplanting.
Question: Could the atmospheric C02/O2 levels be an issue?

Thank you for the additional info.

I seriously doubt atmospheric CO2 has anything to do with the challenges you are having.

Suggest you add a small fan that's connected to a timer. Perhaps you can use the same timer as for your lights. (Or is that a person at the light switch?) The fan will help alleviate the "low air circulation" issue. At the same time, the fan may help the plants to move a bit, thereby also helping to them to develop sturdy stems.

With the increasing outdoor light and temperatures, I would expect the plants to progress well from this point forward.

I implemented all your suggestions but the wilting problem is getting worse. Other plants (peppers and melons) are growing in the same medium and the same conditions and seem fine. The wilting seems to be moving up the plants, affecting first the lower branches, then higher ones. They wilt and eventually fall off. It almost seems like a vascular disease.

Thank you for sending the update.

The peppers and melons appear to be doing well except that they are leggy. Your light set-up sounds as if it should be fine. So, I wonder if the variation between day and night temperatures is too low. In general, a differential of 20 degrees between day and night temperatures is advisable to grow sturdy plants. If the space heater is maintaining 60F at night, either turn the heat down or off.

The tomatoes are a bit puzzling when the other seedlings are doing so much better. I wonder if it is connected with your watering method. (You wrote "Plants are watered a small amount daily to avoid saturating the soil. No run-off has been observed.")

The guideline for watering potted plants is to moisten the entire root zone and to allow for 10 percent runoff. The runoff (drainage) helps ensure that fertilizer isn't accumulating within the root zone where it can damage the tender absorbing root hairs.

Consider moving the plants outdoors now. The current weather conditions of light overcast and nicely warm daytime temperatures should help make the transition an easy one. As I suspect you already know, it's important to harden them off gradually - start the pots in a protected and shaded place, then eventually transplant into the garden.

The melons should go into the ground soon. The larger the root system when they are transplanted, the more likely the plants will suffer a set back.

If you are concerned about the outdoor temperatures dropping too much for the seedlings, consider using row cover. (See "How to Install a Floating Row Cover -

Hope this helps. If you have time, please post an update.

I shut off space heat and increased watering rates as you suggested. The problem seems worse and I'm now having trouble with the previously healthy pepper plants as shown in the attached photos. Since it has spread to a new type of plant, I suspect some sort of pathogen. Suggestions? Observations?

Sorry to hear that your challenges are continuing. Common sense suggest that if a new regimen made things worse, it's likely wise to revert to your previous practices.

If you have extra seedlings, you might move several into the garden bed to see how they will do. But because the nights have been rather cool, the seedlings will need the protection of row cover, at least overnight, (Or perhaps a frost blanket or individual hot caps.)

Have you tracked the temperatures since the heater has been turned off. If so, what have they been?

I've contacted another expert for his opinion. He has access to this exchange and may respond online. So, the new problem, as I see it, is this is Friday. (Few experts respond on weekends.) I will immediately post any info I receive.

The expert I consulted said that the new symptoms on the peppers suggested edema, also spelled oedema. (Edema creates the slight pebbliness you see – and feel – on the leaves.) The most common causes are warm wet soils, high humidity in the air, low wind, and overcast (cloudy) skies. (In other words, the same as our recent weather.) At such times, roots absorb water faster than it is lost through the leaves.

The bottom line: Edema is not a disease.

With time, the small bumps will become corky and obviously raised, typically on the undersides of the leaves. Even so, the seedlings will not be damaged and will soon develop fresh, new, normal leaves. As long as the transplant process goes well, you will ultimately have the abundant harvests you expect.

I encourage you to start hardening off the seedlings over a 2-week period. Set them outdoors in a protected, shady site during the day, gradually increasing the number of hours per day, and take them in at night. Then get them into their final garden bed. If temperatures dip, protect them with row cover . (The link I sent previously offers several methods to apply row cover.)

Good luck, and enjoy your garden!