Cylindropuntia germination experiment

[Shane]

I started an experiment on C. imbricata seeds this February. I wanted to test whether chipping or freezing had better germination. Initially I used two groups of seed. One was chipped and planted immediately, the other was frozen

Since 2/4, only one of the 68 chipped seeds has germinated. Before I planted the frozen seeds (last week), I decided I need to do another batch of seeds for a better control. I planted four groups in all: Frozen and chipped, frozen and not chipped, not frozen and chipped and not frozen and not chipped. There's been one germination so far [EDIT]: in the not frozen but chipped pot

Here are the details
Plant date:

2/4/2020
Group 0
68 Cylindropuntia imbricata seeds. Soaked overnight and planted in open air on my porch. Frequently watered to keep the seeds moist

4/11/2020
Group 1
34 Cylindropuntia imbricata seeds. Frozen for 10 weeks then soaked for 5 hours. Planted in sterile soil in humidity under artificial light
Group 2
34 Cylindropuntia imbricata seeds. Frozen for 10 weeks, chipped, then soaked for 5 hours. Planted in sterile soil in humidity under artificial light
Group 3
34 Cylindropuntia imbricata seeds. Chipped, soaked for 5 hours. Planted in sterile soil in humidity under artificial light
Group 4
34 Cylindropuntia imbricata seeds. Soaked for 5 hours and planted in sterile soil in humidity under artificial light

All seeds are from the same seed pod, season of 2017. I plan to remove the humidity after a month or two and place the plants outside. The frozen seeds were frozen in my kitchen freezer at a temperature around 0F (-20C). I used nail clippers to chip the seeds (where applicable); I tried to cut as close to the embryo as I could without cutting into it

I will post updates as the experiment goes on

[Shane]

So far I've had two germinations each of the ones that didn't go in the freezer (groups 3 and 4). Still nothing from the frozen ones

[esp_imaging]

I'll be interested to see how this develops.

I sowed Opuntia imbricata 2 years ago. From memory, I got about 50% germination within 2 months I think, no special treatment (maybe soaked overnight, but no chipping or scarification etc). I can check my records (not on this computer) if you are interested. So it seemed for me it wasn't a "hard to germinate" species, unlike various Tephrocactus etc.

[Shane]

I can check my records (not on this computer) if you are interested. So it seemed for me it wasn't a "hard to germinate" species, unlike various Tephrocactus etc.

I'm pretty inexperienced with Opuntiads, and am doing the experiment to try to make some sense of growing them from seed before I move on to harder ones. I chose C. imbricata because I have a ton of its seeds

I would be curious to compare notes with you. I'll keep you updated on how it goes

[Shane]

An update:

Group 0 (no treatment, not sown in humidity)
1 germinated (no change)

Group 1 (frozen)
2 germinated so far

Group 2 (frozen and chipped)
No germination

Group 3 (chipped)
3 germinated so far

Group 4 (not frozen or chipped)
6 germinated so far

I don't think there's enough here to draw any conclusions, though I might hesitate to chip Opuntiad seeds in the future

[esp_imaging]

It's early days yet.
I'm still getting germination from O. basilaris sown about 2 months ago, it wouldn't surprise me if it continues for another month or 2.

I find Opuntias often respond to heat - maybe get them (or selected sets of seeds) up to 30deg C or higher during daytime for a few day and see if you get burst of germination a few days afterwards .

[Aloinopsis]

it wasn't a "hard to germinate" species, unlike various Tephrocactus

Why are Tephrocactus hard to germinate?

[esp_imaging]

it wasn't a "hard to germinate" species, unlike various Tephrocactus

Why are Tephrocactus hard to germinate?

Good question, but they are!
Other associated genera (some Cumulopuntia?) have a reputation for being exceptionally difficult.

I tried at least 6 packets last year of Tephrocactus, Cumulopuntia & Austrocylindropuntia and only had 1 seed germinate. I tried soaking, chipping, scarifying, drying and rewetting, and I'm trying again with the same seed pots this year, with no further germination.

[Aloinopsis]

I planted 14 Tephrocactus seeds last year and 6 germinated within 2 months. I did not realize they were supposed to be difficult.

[esp_imaging]

I planted 14 Tephrocactus seeds last year and 6 germinated within 2 months. I did not realize they were supposed to be difficult.

Well done! What species, and what was your method / conditions?

[Aloinopsis]

I planted 14 Tephrocactus seeds last year and 6 germinated within 2 months. I did not realize they were supposed to be difficult.

Well done! What species, and what was your method / conditions?

They were Tephrocactus alexanderi. I didn't do anything different, I put them on a timed heating mat with all my other seeds. I normally turn the heating mat off at 8 weeks, which is also generally the first time I check on seedlings.

[esp_imaging]

That's a great result!
According to http://www.llifle.com/Encyclopedia/CAC ... alexanderi, "Seeds are extremely difficult to germinate."

[Shane]

There hasn't been any further germination. I think I'm going to end the experiment and put the plants outside where they can get better light

My conclusions are:
1. The sample size wasn't large enough to yield much statistically significant data
2. Freezing doesn't seem to have a large effect on germinate rate
3. I still don't have a great idea of how to germinate opuntiad seeds. They clearly need humidity for germination (see group 0), but also brighter light than I can reasonably provide artificially (if I move them any closer to the light, the plastic bags could melt, or worse). I'm at a loss as to the proper way to germinate Opuntiads. The only option seems to be in bags outside, but I'm afraid that an enclosed environment (bag) outside would get too hot. Maybe a tray in a greenhouse with misting would work, but I don't have a greenhouse

[esp_imaging]

3. I still don't have a great idea of how to germinate opuntiad seeds.

It's possible that with the types of treatments available to most amateurs, they normally germinate erratically, so searching too hard for a method to get consistent, quick germination, like for most other non-opuntiad cacti, may be a waste of effort.

[samhain]

The first seeds I tried were Opuntia basilaris, I pulled them from a native plant in my yard. Did the baggie method indoor, poor light, 70s temp, no special treatment. I don’t recall when they were started but they were sufficiently dry, crushed the dry fruits to get the seeds. Had near 100% germination. Killed all but two of them off when I tried to transfer outdoor. Only tried one other opuntiad from seed, a single seed germinated from the fresh fruit, that’s about on par with most the other cacti I’ve tried.