Germinating medium for Gymnocalycium cactus seeds

[PalmatierMeg]

Gymnocalycium has become one of my favorite cactus genera. These species have grown well for me in my sweltering FL climate under a canopy structure where they aren't inundated during rainy season. And they cope with the FL winter dry season better than most cacti. I am growing them in 1/8" diameter pumice and a number of them have flowered and set pods of seeds. From a Youtube video I learned how to harvest, clean and dry these seeds. Today I harvested my seeds. But the Aussie narrator of the video did not show how he mixed his germinating medium or what was in it. His accent was so heavy I could understand little of what he said, except the word, "vermiculite".

Can cactus growers here on PT tell me what they use as a germinating medium for cactus seeds? I want to get my seeds going in the next couple weeks. Thanks.

[Silas_Sancona]

2 hours ago, PalmatierMeg said:

Gymnocalycium has become one of my favorite cactus genera. These species have grown well for me in my sweltering FL climate under a canopy structure where they aren't inundated during rainy season. And they cope with the FL winter dry season better than most cacti. I am growing them in 1/8" diameter pumice and a number of them have flowered and set pods of seeds. From a Youtube video I learned how to harvest, clean and dry these seeds. Today I harvested my seeds. But the Aussie narrator of the video did not show how he mixed his germinating medium or what was in it. His accent was so heavy I could understand little of what he said, except the word, "vermiculite".

Can cactus growers here on PT tell me what they use as a germinating medium for cactus seeds? I want to get my seeds going in the next couple weeks. Thanks.

# Definitely DON'T use Vermiculite for germinating cacti seeds.. 

Best option is a mix or course sand / fine grit ( but not typical fine FL. " sugar " sand ), perlite or pumice ( better ) and a pinch or two of something organic.. ( Cocopeat is the only " organic " thing i try to use ). You're goal is for the mix to stay moist, but not wet, and allow air to move through it as the seedlings start to develop. Once they start looking like tiny mini me-s of your mature specimens, you can allow them to dry out a little more. Avoid direct sun, but also avoid too much shade ( will cause the seedlings to stretch out looking for light )

When you sow them, don't cover w/ soil.. Majority of Cacti need light to germinate/ germinate on the surface of the soil mix. If these are like most other Cacti ( Have seed off one of my own Gymnocals i haven't sown yet ), they should pop pretty quickly ( within a few weeks typically, esp. this time of year )

With most cacti, will be at least a couple years before they reach a size where you can pot them up individually..  Can use small 3" pots, or, if you have a small Plastic container, you can start them in that ( easier to monitor/ keep moisture levels right,  less chance they'll be disturbed or eaten by something while developing ) Some people add a little Calcium in w/ the soil mix to help the seedlings develop a tad faster / stronger. Have pulverized Egg Shells and added to my own germinating mix in the past for added Calcium.

Don't worry about any seed you choose not to sow, Cacti seed is generally viable for several years ( or far longer )

Feel free to ask any other questions.

 

[PalmatierMeg]

Thanks so much for the advice. I hate vermiculite and didn't plan to use it. Based on what you tell me, I plan to use mostly pumice - should I "crush" the 1/8" stuff smaller? - plus a bit of reconstituted coco coir and maybe powdered eggshell. Most of my research indicate I need to sterilize my planting medium in the microwave or oven but is that really necessary? I'm using brand new pumice and pure coco coir and know nothing stays sterile long. I will also take your advice not to sprinkle sand or grit over the seeds. I know that Dyckia and Hechtia seeds should never be covered and it makes sense cactus seeds don't like that either.

 

[Silas_Sancona]

3 minutes ago, PalmatierMeg said:

Thanks so much for the advice. I hate vermiculite and didn't plan to use it. Based on what you tell me, I plan to use mostly pumice - should I "crush" the 1/8" stuff smaller? - plus a bit of reconstituted coco coir and maybe powdered eggshell. Most of my research indicate I need to sterilize my planting medium in the microwave or oven but is that really necessary? I'm using brand new pumice and pure coco coir and know nothing stays sterile long. I will also take your advice not to sprinkle sand or grit over the seeds. I know that Dyckia and Hechtia seeds should never be covered and it makes sense cactus seeds don't like that either.

 

No worries and you're welcome Meg.. 

You could crush it down a bit.. I've had good luck using a piece of shade cloth / window screen -or whatever- and sifted out smaller -sized material when sifting through either the Pumice, or old soil mix, then using the courser -sized bits and pieces, w/ just a pinch of the finer stuff & Coco peat added to help the roots lock in ( learned the hard way cacti seedlings can easily come loose from their position in the com. pot if the soil is too gritty /open )

Depending on the seed size, i've added a thin layer of larger grained Pumice or grit before adding the seed then sprinkled the seed over that. Seed works it's way into the cracks when watered ( i'll use an eye dropper ) and comes up fine.

Was looking over llifle ( a really good site for cactus info ) and appears these like a open, porous soil mix low in pH which means, if you have any, you could add some crushed Lava w/ the soil mix also.. No worries if you don't, just don't add anything like Limestone.. Pinch of Egg Shells shouldn't hurt.

I know some people swear by sterilizing their soil mix first, but i never have ..and have never had any issues w/ diseases, fungi, etc. Our dry heat has killed more seedlings than anything else.