Propagator hazard

[promethean_spark]

A few weeks ago (I think) the timer on my propagator lights broke. Of course it broke in the 'on' position, and since it's on in the evening when I'm home, I didn't notice anything was up, some of the plants looked a little stressed, but that's normal in mid-summer. Then I went on vacation for a week.. Got back to find some mayhem had occurred, continuous light and 90-120'F (it gets hot at noon with the lights on) had been hard on the poor things, but it did sort the xerics from the wannabees. Here's a breakdown:
Trichocereus ssp (various) 80% fatality, the rest very stressed
Mammillaria senilis 100% fatality
Strombocactus (various ssp) 0% fatality, 0% stressed
Ariocarpus (various sp) 5% fatality, rest happy
Ferocactus - doubled in size, looked happy
Turbinicarpus - 10% fatality, but only in the long stemmed types.
Welwitchia - no problem
Blossfeldia - 2% fatality (this surprised me, I expected worse)
Leuchenbergia - 50% fatality
Mammillaria herrarae - 5% fatality, several with burned tops (now offsetting)
Mammillaria schumanii - stressed but ok
Mammillaria grahamii - no problem
Echinocereus lindsayii - no problem
Echinocereus rubrispinus - 50% fatality
Aztekium hintonii - 25% fatality, most of the rest stressed
Aztekium riterii - no problem, they were bigger when I got back
Geohintonia - 50% fatality (biggest disappointment)
Ortegocactus - 5% fatality
Orroya - 10% fatality (I expected worse here)
Gymnocalxium armatus - 5% fatality, rest stressed
Digitostigma - 2 plants, one okay, one stressed
Astrophytum ornatum - all fine
Obregonia - stressed but recovering

I replaced the timer and most of the stressed plants have recovered. I think the % loss overall was maybe 10%, which isn't too bad considering there is about 2000 seedlings in there. I was worried it'd be more like 50%, but a lot of red and yellow seedlings turned green again and recovered.
This is actually the second time this has happened, it seems the timers have about a 4 year lifespan. The first time I caught it earlier when a couple grafts near the light suddenly died at the same time. I'm going to adapt a preventative maintenance interval of 2 years on which to replace it.
The welwitchia wasn't even in a bag and it soldiered through. All the rest were bagged. I am concerned that the dead ones may result in bacteria/fungus that could hurt the survivors, so I'll be graduating a bunch of pots to the GH, and make a few grafts. Fortunately the weather just broke into the fall pattern of moderate temperatures ~70-80/50-60, which is ideal for moving seedlings to the GH.

[Sharpy]

Wow that really sucks! Sorry for the loses.

Can not speak on a lot of these, but the Oretgo, Digi and Astros I would just harden off. Not sure how long they have been bagged, but they all do fine after like 4 weeks or so.

Now to think about when I bought my timer.

[Tony]

Bummer! Especially the Geohintonia.
This is a big part of the reason why I only use my propagator in December and only run the lights at night.
I find it almost impossible to keep things cool enough during the summer in mine.

[CactusFanDan]

Ouch! That's a shame, although it's certainly interesting to see the heat lovers and heat haters. I think all the results you listed are as expected to me. Aztekium ritteri seems to really love heat, I have mine in the hottest part of my propagator.
Echinocereus rubrispinus is a bit of a surprise to me though. I always considered them to be heat lovers.
Mamm. senilis is certainly a cactus which prefer cooler conditions.

Sorry for your losses, but they do provide a certain amount of information to learn from.

[promethean_spark]

Thanks. I was depressed about it for a couple weeks, but now that they're bouncing back I've still got an unreasonable number of little cacti and I've cheered up about it.
Mainly I wanted to give folks a heads up to look out for this problem because it's easy to overlook until damage is done.

Oh, there were Echinocactus horizonthalonus v nicholi in there too, completely unfazed.

[Robb]

Good to now the amount of heat some seedlings can take! I'm just about to sow some Arios, A. hintonii, some blossfelidia and frailea- without a propagator. any suggestions on how much heat to give, or how to provide it?

[promethean_spark]

80'F-90'F is about right for germination.
Don't attempt aztekium or blossfeldia without bagging them, and planning on keeping them in the bag for 2-3 years.
Under shade cloth, maybe even under the benches, in a GH might work at the right time of year. In the house, the best way to warm them is in a box with lights. A heating pad would cost more and not work as well.

[CactusFanDan]

Good to now the amount of heat some seedlings can take! I'm just about to sow some Arios, A. hintonii, some blossfelidia and frailea- without a propagator. any suggestions on how much heat to give, or how to provide it?

Not so sure about Fraileas or Blossfeldias myself, but Arios should ideally be kept very warm and humid without very much light. The less light, the faster they grow initially, but be careful not to etiolate them. I've got A. hintonii growing in the cool compartment of my propagator and they're doing really well. They don't seem phased by strong light, but like to be kept constantly moist. Blossfeldias are fairly similar to A. hintonii, but you may wish to try keeping them warmer.

[Robb]

80'F-90'F is about right for germination.
Don't attempt aztekium or blossfeldia without bagging them, and planning on keeping them in the bag for 2-3 years.
Under shade cloth, maybe even under the benches, in a GH might work at the right time of year. In the house, the best way to warm them is in a box with lights. A heating pad would cost more and not work as well.

ok, my plants are on the windowsill. on cooler days I use a desk lamp to provide some extra heat. Currently I don't use it that much because it over heats easily and that it has a limited range, so only some plants get the light.