Growing cacti (and other succulents) underground

[schmiggle]

There are some cactus species that grow mostly underground in the wild but above ground in cultivation, and in some cases it changes their appearance hugely. The one that particularly comes to mind is Ariocarpus scaphirostris (I hope that's the correct spelling now?), but Ariocarpus trigonus sometimes does it to, as well as Cintia knizei and some Lophophora and Gymnocalcium species (and probably many others I'm not thinking of). This trend is, if anything, more pronounced in African succulents--various Haworthia, Fenestraria, Conophytum burgeri, and caudiciform Euphorbia, for example.

In some cases, I find the underground plants more attractive than the exposed plants seen in cultivation. I've read that putting Haworthia truncata underground makes it rot prone, but it seems to me that Lithops are usually grown by putting most of the leaf underground, and while lithops are known for being rot prone, there's no question that cultivating them is far from impossible. Has anyone tried to grow these other plants underground, as seen in the wild, and if so, what were your experiences?

[DaveW]

Most of these plants retreat below the soil surface in the dry seasons due to contractile roots that pull them down below the surface, probably as they dehydrate. I am more familiar with Thelocephala, now included in Eriosyce. However they go far dryer in Chile for longer periods in habitat than we give them in cultivation, but they will pull down in the pot in winter in cultivation.

An example here if you scroll down the link to T. riperia.

http://forum.bcss.org.uk/viewtopic.php? ... 1&start=30

Bear in mind that this was an exceptionally wet year in Northern Chile in 2015, the wettest for 30 years, so we saw more Thelocephala's above ground and flowering than usual. When my friend visited the same site to following year he could only find a couple of plants since they had all retreated below ground again and the soil blown over them. the Germans call them "earth cacti" from this subterranean habit.

Regarding rotting if the plants are planted low down, that is probably because soil in a pot stays wetter around the body for longer than it would in open ground where it quickly sinks below the level of the plant. If you grow any plants bedded out you will find the top surface of the bed dries out long before plants even in small pots on the staging's do.

[schmiggle]

Dave, that is very interesting. I'm reminded that Yavia does something similar. See, for example:

It's amazing how these plants can grow up through the substrate after being completely covered, sometimes by fairly large stones relative to the size of the plants.

Are there ways to make pots drain more like the ground? For example, one might cut out the bottom and replace it with a metal screen fine enough to keep the pieces of substrate in, make it very deep, use a substrate that's got lots of large pieces of grit. One thing that occurred to me was that one might use net pots, the kind that are often used for hydroponics. I've seen them used often for epiphytic orchids and Utricularia, both of which need excellent drainage and aeration, but I've found a couple of threads where you say not to use them for anything other than epiphytic cacti. Why is this? It seems like the easy way to grow rot sensitive plants, particularly ones with large taproots.

I sadly don't have the space to grow plants in large beds. Hopefully one day

[esp_imaging]

Are there ways to make pots drain more like the ground?

I don't think it's especially easy! In the ground, there is both a temperatue and a moisture gradient away from the surface, so a few cm below the surface it will be significantly cooler (in sunny weather at least) and retain a little moisture. Also the soil continues indefinitely, it's not enclosed in a small finite space (except for plants growing in crevices etc.)
Increasing the porosity of pots (or using net, etc) means that the exterior of the root ball tends to dry very quickly. If exposed to direct sun, it may also be exposed to high temperatures, so may be very detrimental to root growth.
Having a deep pot, filled with consistent potting medium (i.e. no boundaries where different mixes meet, these can hinder movement of water through the medium) helps moisture to be drawn down under gravity.
At the end of the day, the watering regime needs to suit the plant, the medium and the growing conditions. Trying to replicate habitat soil conditions, including depth, porosity etc, only makes complete sense if you replicate habitat precipitation (or dew formation etc) and temperature and other conditions.

[DaveW]

The problem is the Perched Water Table that occurs in all containers used for plants. The difference with deep pots or open ground is the perched water table is further away from the neck of the plant.

See:-

http://oregonstate.edu/dept/nursery-wee ... rties.html

https://davesgarden.com/community/forums/t/719569/

I use net pots for some epiphytic cacti, but find it hard to keep them wet enough. Many epiphytic cacti seem to do better in a normal plastic pot. Most roots are negatively phototropic and grow away from the light, therefore open mesh sides may inhibit them spreading. Epiphytic cacti have ev0lved for their roots to be more exposed to light.

The hydraulic power of plants is amazing, they can push rocks aside, burst their way through asphalt etc, even split their pots if left to get rootbound for two long. Another reason not to grow plants in expensive designer pots unless you are prepared to keep repotting them on.

See:-

https://www2.palomar.edu/users/warmstrong/pljuly96.htm

[greenknight]

There is a way to make pots drain more like they were in the ground - have a wick coming out of the bottom of the pot and dangling down some distance below it. This moves the perched water table down into the wick, outside of the pot.

As for plants growing underground, I do have one. In 2015 I started some Coryphantha maiz-tablasensis seed, got good germination and growth, but then mold got into them - by drying them out I managed to save one. After that I watered it very sparingly from below, never enough to moisten the surface. It grew okay, though slowly, and half buried in the growing medium. I wasn't too surprised - this is the way they grow in habitat.

This Spring I moved it into the smallest pot I had that was deep enough for its tap root, a 2" (5cm) terracotta. I decided to keep it at the same depth it was growing naturally. During a recent heat wave, the temperatures at night were so high that I was concerned the plants were in heat dormancy, so I gave them afternoon shade and didn't water them. The cacti came through just fine - but the little Cory pulled itself completely below the surface. Temperatures moderated a bit, and I gave them all a good watering - the Cory has now re-emerged. Here it is:

Pic-20180809-004.jpg (58.19 KiB) Viewed 2027 times

[kuni1234567]

I have some plants that are growing underground but none of them are cactus or succulents. The problem with growing plants underground is over watering and most plants need sunlight to survive.