Do I need a heat mat?

[Shane]

My seeds aren't germinating, and I'm trying to figure out why. I haven't really had trouble with germination in the past (aside from a couple which in hindsight were bad seed), and I haven't tried anything difficult yet. My growing area is in the mid 60s to low 70s (high teens low 20s C). I can't think of anything else that could be influencing the germination. I'm using the same soil and same light. But there could be something I'm missing. Should cacti seeds generally germinate at those temps?

For reference, here's the results of my latest seed sowing

No germination:
Cleistocactus
Leuchtenbergia
Matucana
Mammillaria
Stenocereus 
Pilosocereus (possibly one)

Good germination:
Ferocactus
Echinocactus

[esp_imaging]

Yeah, I'd up the temp a bit, although you should be getting OK germination with many species at those temps.
A few days at a few degrees higher may speed things up a bit, and is unlikely to do any harm.

[Shane]

Are the cheap ones on Amazon any good? Like this one for example. I read in other threads it's hard to control the temperature without a thermostat, so that and smallish are my requirements

[7george]

My growing area is in the mid 60s to low 70s (high teens low 20s C). I can't think of anything else that could be influencing the germination. I'm using the same soil and same light. But there could be something I'm missing. Should cacti seeds generally germinate at those temps?

Some will do but some will want highs above 25 or even 30 C and lows >22 C so maybe you need a heat mat. I had such an experience with some Mammillaria & Ferocactus. Even in these conditions some seeds will need many tries and several years to germinate so do not through out unsuccessful seeds anyway.
Good luck!

[DaveW]

I use one of these thermostatically controlled propagators in the UK, available from most Garden Centres etc:-

https://www.keengardener.co.uk/stewart- ... gJ1o_D_BwE

Kohres, the German cactus seed firm gives these instructions for seed raising and recommended temperatures:-

https://www.kaktus-koehres.de/Downloads ... ctions.pdf

However some years everything seems to come up like weeds and in others you often get poor germination. I often wonder if it is how good the previous season was when the seed was set? Also we know some seed germinates best when fresh straight out of the fruit, whilst others need to be aged and fresh seed does not germinate very well. Therefore you have to keep the pots of the seed, dry them off at the end of the season and water again next year, or even the year after that in hopes of germination.

In the case of some difficult larger seeds like Sclerocactus etc if they do not germinate growers often pick off the seeds at the end of the year with tweezers, put them back in a packet and sow the following year again in hopes. Seed in nature does not have to germinate when set, it just lies around until it is either old enough or conditions are right for germination.

I did copy these from a scientific test on germination I found some years ago for suggested temperatures:-

GERMINATION2.jpg (103 KiB) Viewed 2911 times

GERMINATION.jpg (125.33 KiB) Viewed 2911 times

[bbarv]

Are the cheap ones on Amazon any good? Like this one for example. I read in other threads it's hard to control the temperature without a thermostat, so that and smallish are my requirements

I got the combo in November 2017. Heat pad still works fine (in use for about 4 month per year) but thermostat lasted only two seasons, you cannot recalibrate it. Still seems to be a good deal.

[7george]

Even a simple mat works well bringing temps ~ 5 C above ambient ones that is good for many seeds. Some additional insulation of propagator can give you higher ones at least until germination. CFL produce extra heat as well.

[Shane]

Thanks for the responses everyone. Turns out there was a lot I didn't know about seed germination and temperature. I think I am going to try the heat mat on Amazon. Side note: I rearranged my seed growing area and my Pilosocereus and M. grahamii seeds germinated after they got moved to a slightly warmer area

[CactiJim]

Yeah, this was a nice thread. I use a heating mat, too, but I just don’t know where to take my seeds off the Heating mat.

I’m also in the Southern California area. (Rancho Cucamonga), but yeah, very informative thread indeed.

[astro_ian]

hello question about using heat mat. Do i leave it 24hrs? and 10-12 hrs grow lights

[Steve-0]

Hello AI...I would expect an expert answer at some point...but for now, yes on the heat mat and 14 hours to 16 on the lights. Heat mat temp according to the chart above. Good luck, ymmv.

[7george]

hello question about using heat mat. Do i leave it 24hrs? and 10-12 hrs grow lights

If you can not arrange temperature fluctuations you'd need from lamps heat (cool light) connect the heat mat through timer as well. But if in that case night temps go too low better leave it 24 hrs. It depends on the setup but typically heat mat increases temp. by about 5 C.