This topic is inspired by the fact that Massachusetts probably received a year's worth of rain in just 4 weeks from mid July 2018 through mid August 2018. With so much rain, even if semps are planted in 100% grit, they can still rot if they never get relief from daily deluge rain, heat, and nearly 100% atmospheric humidity, never experienced a summer like this.

Semp 'Bjorn' seems particularly sensitive, this is the third pot that has gone belly-up and collapsed with rot without notice. As a reminder, my semp mix has been 25% compost and 75% grit, sand, and perlite. It doesn't seem to matter, if receiving an inch of rain every day, and nearly 100% humidity, eve bog plants could rot.


I removed the rotting material from the 'Bjorn' rosette, photograph shows the sturdy material remaining, then brought it inside my air conditioned room to dry off for up to a week.



On a different topic I showed a pot full of Semp 'Super Dome' (an arach webby semp) that was distressed with rot, cleaned off the rosettes and kept them dry in my air-conditioned room bare-rooted for a week. Today I potted them up and hope for the best.


Many semps are showing great distress with exposure to so much constant deluge thunderstorm rains (daily) for a month or more. Here is Semp 'Thunder' with about half of the outer leaves showing discoloration and distress, I removed almost half the outer leaves and replanted, the outer leaves still show distress and discoloration but hopefully they will recover. On the right, cleaned up rotting leaves on 'Thunder' and replanted in extra gritty mix.


Some semps sort of look okay, but signal that something is wrong, I noticed that Semp tectorum from Soldeu looked odd, checking the plant I found most of the roots melted away even though in a very lean grit mix, so I'm attempting to salvage them by re-planting in a 90% grit mix.

It sounds like you're doing all you can. I guess the weather you're having is really hard on semps. How are other plants doing? Any others rotting? It sounds like you need some shelters for them while it rains so much.

Boy Mark, I don't see how you do this. What an uphill battle you are fighting. I probably would have thrown in the towel by now.

Perseverance will pay off Mark. The rain has to stop at some point.
Question, is there any way you can grow under a roof? No sides just a roof.

Yes, that is pretty much what you can do for now, grow the semps in much more grittier media since you have more rains and provide some overhead protection if forecasts shows daily rain.

My goodness, I lost track of this topic, so replies to the good comments

plantmanager said:It sounds like you're doing all you can. I guess the weather you're having is really hard on semps. How are other plants doing? Any others rotting? It sounds like you need some shelters for them while it rains so much.

Karen, yes other plants were impacted by the nearly 2-month long high rainfall and heat combination, the nursery owner here suffered lots of rot and losses with tuberous spring plants such as Sanguinaria (bloodroot) and Trilliums. People might think of these spring woodland plants as loving adequately mosit soil, but when they're in summer dormancy they need dryish conditions, the bloodroot in particular is sensitive to rot with too much rain.

MelissaHopper said:Boy Mark, I don't see how you do this. What an uphill battle you are fighting. I probably would have thrown in the towel by now.

Melissa, I couldn't throw in the towel, it was in constant use trying to mop up all the excess moisture ;-)

valleylynn said:Perseverance will pay off Mark. The rain has to stop at some point.
Question, is there any way you can grow under a roof? No sides just a roof.

Lynn, the rain did indeed stop and heat moderated, the last week of August and 1st week of Sept. Some heavy rainfalls here in the last week and a half, but temps are much cooler and the semps look happier, not finding any rotters now. Once I get settled someplace, I would indeed consider building some sort of open air roof for plants sensitive to too much rain.

tarev said:Yes, that is pretty much what you can do for now, grow the semps in much more grittier media since you have more rains and provide some overhead protection if forecasts shows daily rain.

Tarev, I started using much leaner gritty mix, and that seemed to help. In the long run, I don't think growing them in such an austere lean mix will harm them in any way.

Following up on a rotter I spot back in the 3rd week of August, is 'Veleda'. First photo shows my initial salvage effort, where I removed all rotting parts including 60-75% of the leaves, and carefully gouged out the soft rotting parts of the tap root base. Then dried the rosette inside the house in an air conditioned de-humidified space for a week or more, then planted it out in an extra lean mix. I hadn't looked at it for a couple weeks, was pleased to see it looking so fresh this morning, second photo.

Mark your reclaimed 'Veleda' is looking beautiful. Good save.

valleylynn said:Mark your reclaimed 'Veleda' is looking beautiful. Good save.

I have several more pots of Veleda, so this one was added to one of my 7 Semp Trays, for donation at my talk in October, it's fast approaching.

It'll be here before you know it. Time sure does fly.

Haven't had problem with many "rotters" once we got past the HHH days of summer with extraordinary rainfall amounts and record consecutive days of rain. Beginning of Sept we had some relief from heat and rain, but that was short-lived, latter 2/3rds of Sept we had RAIN, Rain, and more RAIN...beginning of October has been _________ (rainy is the right answer), spotted another rotter today, it was 'Chocolate Dip', I had 3 chicks, the biggest one is a loss, I salvaged a small one, and a tiny one.

Photo closeup after rot-removal surgery, half of the rosette was removed, it's now drying for a week in my room before going back out again. While we can get light first frosts in October, serious freezing typically holds out until mid-late November, so there's still some time to get it healed back in before a winter rest.

Wow, Mark you have really been getting some very trying weather conditions.

Semps here are so happy with a very occasional rain and cool weather, daytime in the 60's with night time in the low 40's. This make for some happy semps.

valleylynn said:Wow, Mark you have really been getting some very trying weather conditions.

Semps here are so happy with a very occasional rain and cool weather, daytime in the 60's with night time in the low 40's. This make for some happy semps.

Yes, I agree. There can be days of rain where one gets 1/2", and then there are days of 3-4" of rain, over and over again, we're getting that, everything so drenched and no chance to dry out. This is not normal, we are WAY OVER normal rainfall amounts. At least with cooler weather, this Chocolate Dip rotter was the first in the last month. Hope I can save it.

Mark can you put it somewhere that it won't get rained on?

valleylynn said:Mark can you put it somewhere that it won't get rained on?

I'm going to build two open-air rain/snow covers, quick and dirty 2x4" slanted roof construction, plastic on the top slanted roof but open on the sides, will be able to use it in summer too. After my semp talk on Oct 20, that's the first order of business. Next year we might be the Sahara Desert like we were in 2011 & 2016, weather has become so unpredictable and erratic.

Great plan Mark. And yes, we just never know what next year will hold for us in the weather conditions.

A large number of my 'century' semps bloomed this spring - more than I have ever had bloom at one time. I attributed it to more than average rain also. Not really much rot - but they are very hardy - but they sure did bloom all over the place.