Recognition

[Cachi]

Hi,

which species? I got these guys from a friend so no tags on them.

[Steve Johnson]

Unfortunately I can't help you on the ID, but I did want to make a couple of observations. First, your mix appears to be nice and lean (in other words, not too soil-heavy, so that's good drainage and aeration of the roots -- what desert cacti need). But second, the pots are way too big for the plants, and their roots won't be able to take up all the water in such a big pot. Here's the basic "rule of thumb" for sizing pots properly:

• Diameter -- a 1.5 cm-2 cm margin around the root ball or the base of the plant, whichever is bigger.

• Depth -- a 1.5 cm-2 cm margin between the lowest root and the bottom of the pot.

You'll need to take the cacti out of the pot, measure the diameter of the root ball or the base (once again, whichever is bigger), and measure the length from the base to the lowest root. Then you'll be able to determine the correct pot size. You can get away with pots that are a little bigger, but a lot bigger causes serious problems over time. By the way, I think your 2 Pilosocereus azureus are also too big for their pots, so you may want to investigate that.

[Cachi]

Thank you for your reply. But can you explain me how a pot could be too big? In nature they don't have a limited area.

Regarding my Pilosocereus azureus, are they too big for the pot or is the pot too big?

[greenknight]

Pot culture is very different from growing in the ground - excess water is drawn away by the surrounding soil in the ground. In a pot, only the force of gravity drains it, and it's a weaker force than the adhesion of water to the soil. Soil in the bottom of the pot remains saturated until the plant takes up the excess water. For a fuller explanation, see: http://gardening.stackexchange.com/ques ... ater-table

[Tom in Tucson]

My guesses:

The cluster on the left looks like a Euphorbia. Either E. tubiglans, or a hybrid with E. polygona.

On the right the stems appear to be withered Echinocereus viereckii var. morricalii.

Steve's suggestions for pot size are very valuable. Be sure to wait at least a week after transplanting before watering.

[Steve Johnson]

Pot culture is very different from growing in the ground - excess water is drawn away by the surrounding soil in the ground. In a pot, only the force of gravity drains it, and it's a weaker force than the adhesion of water to the soil. Soil in the bottom of the pot remains saturated until the plant takes up the excess water. For a fuller explanation, see: http://gardening.stackexchange.com/ques ... ater-table

Spence is absolutely correct, and I have a feeling that most beginners aren't aware of what he just said. With that in mind...

Regarding my Pilosocereus azureus, are they too big for the pot or is the pot too big?

The pot is too big for the plants. More specifically, the pot is too big for their roots.

My guesses:

The cluster on the left looks like a Euphorbia. Either E. tubiglans, or a hybrid with E. polygona.

On the right the stems appear to be withered Echinocereus viereckii var. morricalii.

Good catch, Tom. Although all cacti are succulents, not all succulents are cacti. Cachi, see this:

https://www.cactiguide.com/cactiornot/

I'll pull out a quote pertaining to the Euphorbia Tom mentioned:

• "Perhaps no other taxon is more commonly confused with true cacti than that of Euphorbia. Some Euphorbias look more like a stereotypical cactus than even some cacti species. Euphorbias can be found all over the world, but most originated in Africa. If you cut a Euphorbia, it will secrete a sticky, milky-white fluid. This fluid contains latex. Flowers of Euphorbias are typically small nondescript buttons with no sepals or petals. Many Euphorbias also have thorns, making them appear even more similar to cacti. Upon closer inspection, however, one can easily see that these are not a separate spine arising from an areole like that of true cacti."

Regarding cultivation, there's a significant difference between cacti and succulents:

• Cacti grow in spring and summer, then go dormant in fall and winter. (This applies to the northern hemisphere. The growing and dormant seasons are flipped around in the southern hemisphere.)

• Succulents are either summer-dormant or winter-dormant. Knowing which is which will depend on the genus.

Euphorbia is winter-dormant, so theoretically it can be grown in the same pot as Cachi's Echinocereus (a desert cactus). However, I wouldn't recommend it since cacti and winter-dormant succulents may have different requirements in terms of how often they should be watered during the spring-summer growing season. And there's another problem to consider -- if one plant has shallow roots while the other plant has deep roots, they'll definitely need to be in separate and properly-sized pots.

Cacti and succulents do have one thing in common -- fertilizers good for cacti are good for succulents too.