Hi Jenna,

I'd mention to folks to whom this may not be obvious, this is a type of Euphorbia. Watering gingerly isn't so great for plants, even succulents need good, thorough drinks, given good drainage & appropriate mix.

Sorry but around here folks believe that rocks at the bottom don't actually help anything.

Mush is a serious problem & can spread quickly.

Root rot & related overwatering aren't necessarily always abt too much water. It can be compounded when the bottom soil is still moist & doesn't get a chance to dry out enough btwn watering to get air, which plants need as well.

How have you been deciding when it needs water?

Thanks Karen, I've been watering when soil a couple inches in is dry - a little more frequently now in the summer. It had been growing steadily for months, so I'm baffled. Are you saying you think it could be because the roots were not getting enough oxygen?

There are several genera of damping-off fungi (Phytophthora, Pythium, Rhizoctonia, and Fusariums) that are the bad guys, wreaking havoc on root and stem tissues. Typically, the infection starts in a root and moves systemically in the vascular system to affect additional roots and the stem(s) as well. There is no cure for something as advanced as what we see in the image, but there's a middling chance that propagation of one of the appendages growing from the stem toward the top would be successful.

Large stones used as ballast are effective at reducing the amount if excess water a soil can hold, but drainage layers exacerbate the issue.

The images illustrate how ballast works as a positive method for reducing excess water, and how drainage layers cause water to "perch" above the drainage layer.

Al

Al — so are you saying this is a fungal infection?! If so, was there anything I could have done to prevent it?

Also the drainage I am using are lava rocks - they are large and porous acting much like the bricks in your illustration. Obviously can’t use actual bricks for many plantings in smaller containers. Thanks for your input!

1. A tetrahedron is a 3 sided pyramid + the base. It's often used to illustrate what is required for a disease to prosper by labeling each of the 4 facets/sides with one of the requirements for a disease to infect an organism. There must be a population of virulent inoculum present (fungal spores) large enough to begin the disease process, and the inoculum must be able to genetically recognize a/the host.
2. The environment must either stress the host and weaken its ability to defend itself, or favor an increase in the numbers and movement of inoculum. In this case, It's likely that too much water and too little air in the rhizosphere/root zone both caused the plant stress and favored multiplication and spread of the fungi.
3. The host must also be susceptible to the particular pathogen
4. The 4th side of the tetrahedron is time. Conditions have to favor development of the disease over a period long enough for it to develop to the degree it can overcome the plant's defenses.

All 4 of these conditions are essential to the development of an infection. In order to prevent a disease, it is only necessary to eliminate 1 of the 4 facets from the tetrahedron. Regarding #1 above: There is no way to know where the disease originated, but cleanliness (clean up old dead parts of plants, don't use old soils, sterilize pots after/before use, ..... is helpful, as would be using a soil that has excellent air porosity at container capacity (when the planting is holding all the water it can), and watering judiciously. #2 Regular checking of moisture levels with a wooden tell is very effective when it comes to avoiding over-watering, but there are other factors that contribute to the plant's vulnerability - high root temps, low fertility, low light levels, a generally depressed metabolism due to any cause, .... #3 Not much you can do after the fact about susceptibility, but researching for info about cultivars that are resistant (mainly for plants in the landscape) can be helpful. #4 The time factor often involves prolonged periods that stress the plant and favor the pathogen. Monitoring moisture needs carefully, shading pots to keep root temps low at midday, and anything else that reduces the amount of time the plant has to endure conditions at the extremes of what it's genetically programmed to tolerate, along with making sure conditions do not favor the pathogen can stop it from gaining traction.

Without really knowing what the underlying cause was, nothing specific in the way of what you could have done to avoid the infection, but being able to consistently ensure your plants are in a good soil, one that can be watered to beyond saturation so the soil is being flushed whenever you water is the largest step forward you'll be able to take at any given time. IT makes everything sooo much easier.

If you're interested enough in doing some homework, let me know and I'll provide some links I think you'd find helpful.

Al