Pumice & Cacti

[PalmatierMeg]

A few years ago I had a large container garden of cacti but years of FL humidity and rainfall decimated it. This climate is unkind to all but a few species. I've since acquired a 10 x 16' garden shed that has one large window each on the east and west ends plus two small ones on the front. And that got me thinking: maybe I'd have a better chance growing cacti on the window sills. Humidity might be an issue but rain would not. My collection would have to be small in number and size, so I am focusing on several genera: Sulcorebutia/Rebutia, Eryosice, Turbinicarpus, Neoporteria, Obregonia, Strombocactus and Pelecyphora. I managed to salvage several Turbinicarpus still surviving and some small Gymnocalycium(?). Yesterday my husband installed shelving in the east- and west-facing windows.

But I got to thinking. I need create a specialized soil mix for these guys. Many posters here have praised the addition of pumice (over perlite) to create a lighter, well-draining potting mix for all their plants. Problem for me is almost no one in the nursery trade here even knows what pumice much less stocks it. And it is expensive to ship here. Still, I bit the bullet and ordered about 10-12 lbs of it which I will designate to cacti, my Agave pumila  and maybe my smallest, most valuable palms.

I need advice on what fraction of my new mix is to be pumice vs. fraction of cactus/palm soil (MG brand) in my humid climate. Also, do you suggest additional additions or substitutions? I plan to be very parsimonious with watering and water only from below. I give my A. pumila hardly any water at all and it seems to be doing fine. I'd planned to leave it outdoors all "dry" season but we've had nothing but dreary, chilly, rainy weather so I put it back in the shed. In summer the shed will get hot inside but we do have a roof vent to release some heat.

Ideas? Thanks

[Silas_Sancona]

Meg,

Best ratio that has worked out well for me  has been no less than 50% Pumice as the main ingredient for cacti and succulent mixes. I also add things like Gro-stones and calcined Clay, Aka Turface- the stuff they often use to skin baseball fields. Have also taken decorative stone sometimes known as "Timberlite" (Lightweight, earth colored Lava Rock) and crushed it to smaller sizes for top dressing, or incorporation in a given soil mix. Any Potting soil or Organic stuff should make up no more than roughly 5-10% of the same mix.

As for placing, most of my cacti have stayed outside sheltered on a wood slatted bench i built which is covered with plastic coated screen on the top and sides with some gaps built into it to allow for air circulation. The open side of the bench faces east so the cacti are sheltered from the sun in the afternoon. Worked very well keeping out rain during the summer. Echinopsis and Pachypodiums grew like crazy. That being said, i lost all of my Rubetia and Sulcorebutia.. they really hate our heat/humidity, regardless of how they were watered. I did throw a couple pieces of my Echinocereus pentalophus (Lady Finger Cactus) under my larger potted Rio Grande Cherry out in the yard and all in all, they handled the heat/humidity and rain well..

Agree that Pumice( in any quantity) is hard to come by here.. had to go to a Hydroponics store up in Tampa to find small bags of it. Same with Gro Stones though i have seen one of the big box stores offering it in their online catalog recently. Bags of Calcined Clay can be found at any of the well known Landscape/tractor supply locations.

Hope this helps,
-Nathan

[PalmatierMeg]

1 hour ago, Silas_Sancona said:

Meg,

Best ratio that has worked out well for me  has been no less than 50% Pumice as the main ingredient for cacti and succulent mixes. I also add things like Gro-stones and calcined Clay, Aka Turface- the stuff they often use to skin baseball fields. Have also taken decorative stone sometimes known as "Timberlite" (Lightweight, earth colored Lava Rock) and crushed it to smaller sizes for top dressing, or incorporation in a given soil mix. Any Potting soil or Organic stuff should make up no more than roughly 5-10% of the same mix.

As for placing, most of my cacti have stayed outside sheltered on a wood slatted bench i built which is covered with plastic coated screen on the top and sides with some gaps built into it to allow for air circulation. The open side of the bench faces east so the cacti are sheltered from the sun in the afternoon. Worked very well keeping out rain during the summer. Echinopsis and Pachypodiums grew like crazy. That being said, i lost all of my Rubetia and Sulcorebutia.. they really hate our heat/humidity, regardless of how they were watered. I did throw a couple pieces of my Echinocereus pentalophus (Lady Finger Cactus) under my larger potted Rio Grande Cherry out in the yard and all in all, they handled the heat/humidity and rain well..

Agree that Pumice( in any quantity) is hard to come by here.. had to go to a Hydroponics store up in Tampa to find small bags of it. Same with Gro Stones though i have seen one of the big box stores offering it in their online catalog recently. Bags of Calcined Clay can be found at any of the well known Landscape/tractor supply locations.

Hope this helps,
-Nathan

Thanks Nathan. I'm not familiar with any of the stuff you mention so will have to do my research. Sounds like I should back off from too many Sulcorebutia/Rebutia. I noticed many of them come from high altitudes. Too bad. Hope the ones I have make it.

[SHEP]

I am in Bay Area, west of Berkeley.  I have warm 90-95 degree Summers.  I have many cactus and succulents, most in pots (non winter hardy).  I use a potting mix of 50% pumice, you could substitute perlite, and 50% of my own compost.  It works well for me.  I use 100% pumice for my Aloes.  Some people substitute peat moss, but, I don't think that its a good idea.  I would use the Palm/Cactus Mix as a substitute for the organics.  Most of these plants are situated in morning sun. I have been using this mix for about five years.  I am not sure it matters what you use for Agaves, as they can take the heat.  I suggest looking at San Marcos Gardens in Santa Barbara, CA, for browsing.    Cecile

[Silas_Sancona]

Not a problem Meg..

Not to tempt you too much, but here are a few of the Echinopsis i have that held up well here:
#1Echinopsis "Sorceress"
#2 Echinopsis "Fuzzy Navel"
#2 Echinopsis "Sierra Skyline".. Pups like crazy
#3 Echinopsis "Fond Adeiu" Slow to pup but flowers change from Pink to Orange. 8" across
#4 Echinop/Trichocereus "First Light" spectacular.
#5 Echinop/Trichocereus "Flying Saucer"Flowers on this specimen at the Huntington were 8-9" across. Flowers can reach 12". Can't wait until mine flowers.

[PalmatierMeg]

Fabulous flowers!

Thanks, Cecile. I know of them and will look into it.

[John Case]

Meg,

I have access to pumice but must but a yard at a time......I am running low but may have to bite the bullet this year and get more....80 bucks plus driving the truck 80 miles.....

the things we do for our plants.......sheesh....

[SHEP]

John, you can buy pumice in bags at American Soil in Richmond, CA.  I usually get mine up in Medford, OR, where I buy in bulk and have a choice of three different sizes.  I use the pumice fines, for some of my alpine plants.  I have had some small, grafted Daphnes, live in this for several years.