So, I would love some wiser gardeners than I to weigh in on this! Sometime in, oh, probably July, I purchased two beautiful white phlox, tall ones, and no ID saved here. Planted both and both did well until about a week or two ago when one started to die. They are maybe 14 inches apart. Exact same conditions and care. Well, some condition must differ, but what?

We have had other plants mysteriously sicken and die too. A Liatris, when the others are still doing fine, and a couple of coreopsis in a patch grown from seed -- actually, three of those have withered and died.

At first I thought "cat urine" because there are two resident outdoor cats and I know one at least uses the beds as a litter box. But since these two are showing such a distinct contrast, and in case there is some other likely cause, I wanted to ask.

And, can cat urine really do that much damage? Bummer! Imean, I know it's not good, but did not know it could be deadly.

Pictures, first the dying phlox:



right next to it, the healthy phlox:

Nah, Kyla I don't think you can blame the cats. I've had outdoor cats for years, and never had a plant killed by cat urine. They don't pee enough at one time, nor do they do it in the same place. You'd be able to smell it if they did. Rain and irrigation would wash it away in any case.

Now, human urine can kill a plant for sure. Urea is a component of many fertilizers, but too much in one place can burn. That plant does kind of look burnt, with the crispy brown edges to the leaves. Maybe it got too much fertilizer? Or if you do have anyone at your house (it's usually the guys . . . ) who likes to 'go' in the yard, tell them not to do it in one spot, spray it around.

I don't know much about phlox, as they don't grow here so it's been years since I grew any, but I'd hurry and dig up the ailing plant, and take a good look (and smell) at the root system to see if there are grubs, fungus or some other problem underground? Otherwise, for something to up and die that suddenly, I'd suspect overspray of some sort of weed killer or even lawn fertilizer from the neighbor's "lawn".

You might actually be able to save it, if you rinse off all the old soil, let it rest in the shade in new potting soil for a week or two, and then plant it out again, somewhere else. OR, if you still have the receipt (I know, I can never find them) you could take it back to where you got it. Most places will guarantee a plant for a year - especially if you say you bought two, and one is still doing fine.

The grass behind looks rather droughty. When you bought the plants were they established plants in soilless media in a pot, or were they plants that were dug up for a plant sale or something like that? If the first, was the pot watered well before it was planted? As Elaine said, the leaves are scorched on the edges, which could mean too much fertilizer. It might also mean drought. That can happen even if you water a lot after planting if a root ball of soilless media has dried out significantly. If you lift it as Elaine suggested you would be able to see if the media is overly dry. If it is, soak it in a tub of water before replanting. It sounds as though it had only been in the ground a couple of weeks before it started its decline?

As far as Liatris is concerned, I had some wiped out this year by voles chomping on the roots.

Huh. Okay, well, I am relieved I don't have to blame the cats.

No guys live here, so that's out.

We don't use either artificial fertilizer or weed killer, but we have indeed had a very dry season. That grass is in the neighbor's yard. Our's looks a tiny bit better due to my watering occasionally.

What it looks like to me in every instance is the plant's roots reached a zone where something inhospitable to it lurked. What that might be? No idea. My housemate says she hasn't used Miracle Gro in years. I know her yard guys have used Roundup on the lawn but as of this spring they no longer do. I suppose they might have used it in the beds too (and I know it's a controversial subject whether it stays in the soil, some say no some say it does) -- even if so, even if it stayed that long, would there be those little pockets like that?

Neighbor, nope, she only has her grass cut every week or so and that's it.

As for the original plants, they were purchased at Southern States, were potted in some kind of potting mix, were healthy and watered at the time of purchase.

I'd guess they've been in the ground for a month.

Hmm. Well, I might just dig that one up tomorrow and see what I can see. I won't bother trying to take it back because it's not really on anyone's flight path to go there, so more hassle than it's worth. Plus I feel pretty sure it wasn't the plant or the care they gave it that is the problem here.

Thanks for the help! and if anyone else has a clue, I'm all ears.

I know it does happen sometimes, but RoundUp wouldn't routinely be used on a lawn for a general application, it might be used for spot treatment. It's non-selective so doesn't discriminate regarding what it kills. While it's controversial whether there is some residue that remains in the soil, it is not, and doesn't remain, active as a herbicide in the soil. What is often used on lawns is a selective weedkiller and the triple-herbicide ones often do contain a soil-active herbicide. I think it's doubtful it would cause that isolated a problem though this long after. Has anything else died besides the coreopsis, liatris and phlox? Any odd branches on trees or shrubs or anything like that?

Yes, the Roundup here was only used for spot treatment.

And nothing else -- well, no, one other plant followed the pattern, a Dicentra, but it wasn't in great shape when I bought it and again, the soil is generally pretty poor. Still, that one, I hoped to nurse back into shape, and instead, pffft!

"human urine can kill a plant for sure"

Elaine, this gave me such a chuckle! Long, long ago, when my now-husband-of-24-years and I were first going together, I was living in a cabin that was really in the middle of nowhere -- he was a "city boy" and loved that he could go out at night to pee off the deck (this is definitely a "guy" thing)... I kept telling him he was going to kill all my grass, and yet it grew more rampantly there than anywhere!!

Back to the actual subject of this thread... Kyla, sometimes plants just "croak" -- it can be very frustrating when there is no apparent cause!

I just dug up the ailing phlox, and found what looks like a fungus. The first area I found was down in the root mass, but then when I looked closer I found a patch right next to one emerging stem. Meanwhile, the healthy plant a foot away was wafting its sweet scent into the air, and it was starting to sprinkle rain.

So I got in a kind of hurry. Couldn't wash off all the soil but inspected as closely as I could for more of whatever this is, and rinsed off as much of the root mass as I could without destroying it, filled the hole with plain organic potting soil from a bag, and replanted the phlox. I'll watch closely that its neighbor stays healthyand keep an eye out for more of this stuff. Which may or may not be the problem!

Anyone know what it is? Here are two shots of the little things at surface level, next to the plant stem:



and here is the little patch I found first, deeper in the root mass. My fingers for scale:

If those round things look to you like mustard seeds and you don't usually see them in your garden, look up "southern blight" (Sclerotium rolfsii) on Google. If that looks like what you're seeing you'll need to get rid of the plant and as many of the "mustard seeds" as you can.

I bet that's it. Thanks for the ID!

This is a useful bit of information, from The American Phytopathological Society (https://www.apsnet.org/edcente...)

"Soil amendments, fertilization, biological agents and plant-produced chemicals. Soil can be treated with organic amendments, fertilizers, or biological agents to help control S rolfsii. The addition of organic amendments such as compost, oat or corn straw, or cotton gin trash to soil sometimes reduces southern blight incidence and development. This effect may be due to the increase of toxic ammonia and/or the increase of certain soil microorganisms in the soil. Furfuraldeyde, an organic (sugar derivative) amendment, has been shown to change the soil microflora, and this change has been related to a decrease of S. rolfsii in the soil in lab and greenhouse studies. Also, neem oil and pine bark extracts or pine bark powder have resulted in reduced growth of S. rolfsii. To date, these amendments have not been widely used for disease control, but future refinements may allow their use in the field. Fertilizer studies have shown that treatments with ammonium, calcium nitrate or calcium sulfate may help control southern blight. Increased nitrogen may inhibit sclerotia germination, alter host susceptibility, or alter the soil microorganisms. Biological control of S. rolfsii has been achieved to some degree with bacteria (Bacillus subtilis), actinomycetes, a mycorrhizal fungus, or certain Trichoderma species. There have been several studies to attempt to explain the mechanism for Trichoderma inhibition of S. rolfsii. Many studies have shown disease control by biological agents in laboratory and greenhouse tests, but disease control is less effective in the field. When control is seen in field studies, the required quantity of the biological product may be very high and not practical in most agronomic situations. In addition to the above, certain compounds in some aster roots and mustards are being studied for their inhibitory activity against this pathogen. ..."

Kyla, also you might want to throw some shade cloth (or any old piece of cloth) over that plant for a few days until it recovers from the digging up and re-planting.

If you have any Neem oil concentrate, I'd recommend mixing some up in a watering can and giving both your Phlox plants a douse with it. I've had some success against blight doing that here. (and your article mentions it!) We have every blight known to man in Florida.

I have no Neem oil, but I do have alfalfa pellets mixed with manure which are quite ammoniac and generate actinomycetes freely. I spread some of those on the soil.

Since this is a cottage garden type situation and not a commercial growing operation, I am going to take a low key and slow approach of working away at balancing the soil -- because I feel that is the best solution anyway, and really the only one available to me.

I'll get some Neem oil too, first chance I get.

As for the shade cloth, we are having an overcast day and it's forecast to be rainy and cloudy all week, so I think hot sun won't be an issue. If the weather shifts I'll probably do that though. Thanks!

This is a serious disease, it's not worth trying to save the plant, it needs to go, and the sclerotia, and the soil it was in. Quoting from the above article, and others on the disease will say the same:

"As with many plant diseases, removal of infected plants is an important aspect of disease control. Sclerotium rolfsii usually causes infection at the lower stem (crown) section of the plant, and once infection takes place, removal of the whole plant is necessary. Prompt removal of infected plants will help prevent the addition of abundant fungal inoculum to the soil. If infected plants are allowed to remain in an area, these plants will serve as a continuous source of inoculum. Plant removal is a practical measure in landscapes, gardens, nurseries, and greenhouses, but not in field situations."

Oh, good point about removing the plant, Sue. But if the fungus is also in the soil, shouldn't the soil around there also be treated, and unaffected plants around the area?

Kyla, alfalfa pellets are a fantastic soil amendment, and as you say they add and generate actinomycetes which surely will help with long-term health of your soil.

The other thing to do after frost kills things back in the fall is to till the soil up wherever you've had these problems in hopes that freezing temps will kill off the pathogens.

Down here we don't have enough cold to do that, so instead, we 'solarize' infected soil by covering with clear plastic and letting the sun bake the soil. If this continues to be a recurring menace for you, this is another good, non-chemical treatment. I solarize my garden in small segments, as I clear out an area. Up where you live, it's best to do this in June when the sun is hottest.

You know, this is the kind of situation I run into, having moved around more than I'd like, and gardening where I land, doing what I can with what I find, etc.

The soil here is out of balance, that's visually apparent in the plants, or was to me right away. The more intensive methods of repair are often just not practical for me. In this instance, the various locations this "sudden plant death" have arisen are ... various. Until this one, the plants have stayed in the soil for a while. What's next to those spots -- things are healthy, so far. The entire length of that bed is in process of being redone, and so this is just one more item to factor in.

Meaning, I am not at a stage right now where I am able to mount any kind of major effort targeting any one specific problem. Is this problem so serious I should drop other (fairly urgent and ongoing) tasks to attend to it as a priority? Maybe it is! However, my sense at this moment is that if I am observant and work with the organic solutions suggested in that article (and I will get Neem oil soon as I can!) it is not going to be that dire.

I did remove the diseased phlox, by the way. I'd already disposed of the soil and the blight bits that came off of it. So, next is to get some neem and see if that takes care of it.

Ugh and double ugh to that Sclerotium... I knew there was some reason to like our winters!

Glad to help.