Two cactus in need of identification

[jmoney]

Can anyone identify these two cacti? I have no clue what they could be.

[teo]

Left one is a monstrose Cereus (peruvianus or jamacaru).
I must admit I'm unsure (from the picture) if the other one is a cactus or a Euphorbia. Lower part seems to have single thorns (which might indicate a Euphorbia) but there seems to be multiple spines at the top (which would indicate a cactus). If you prick it with a needle and it bleeds white sap it is probably a Euphorbia.

[jmoney]

What's the difference between a cactus and an Euphorbia?

[jmoney]

Left one is a monstrose Cereus (peruvianus or jamacaru).
I must admit I'm unsure (from the picture) if the other one is a cactus or a Euphorbia. Lower part seems to have single thorns (which might indicate a Euphorbia) but there seems to be multiple spines at the top (which would indicate a cactus). If you prick it with a needle and it bleeds white sap it is probably a Euphorbia.

Here's a better picture of the second cacti in question. It's a little sunburned right now but I am giving it shade using a small plastic pot for most of the day at the moment to give it time to recover.

Also a repeat of my reply. What is the difference between a cactus and Euphorbia?

Not sure why the pic came up sideways but there you are.

[teo]

They are totally different plant families - cacti are from America (north and south) - Euphorbias (at least the succulent ones) are mainly from Africa.
There is much to say about why they look alike but I won't go into that here

[teo]

That picture suggests a Hoodia (yet another plant family from Africa) but I think I will wait for someone more knowledgeable than me....

[greenknight]

What distinguishes cacti from other succulents is they have areoles (spine cushions), which your plant doesn't. I see the resemblance to a Hoodia, but I think they have single thorns only. Maybe Euphorbia virosa.

[Saxicola]

It is a Euphorbia. You could be sure by making a small cut or puncture in it and see if it bleeds white. Euphorbias virtually always have paired spines (if they have spines at all, some don't) just like your plant.

Euphorbias come from all over the world, though most succulent ones grow in Africa. Cacti are only from the Americas. Euphorbias bleed white, very few cacti do, and the ones that do don't bleed as heavily as a Euphorbia. Cacti can have paired spines but usually it is one or many. Euphorbias never have areoles where spines or hairs radiate out from a single point like a cactus. Cacti have showy flowers while Euphorbia's generally do not (I'm tempted to say virtually never but that would require a deeper botanical discussion than you may want).

The more cacti and Euphorbias you see the easier it will be to tell the difference when presented with a plant you've never seen before.

[jmoney]

It is a Euphorbia. You could be sure by making a small cut or puncture in it and see if it bleeds white. Euphorbias virtually always have paired spines (if they have spines at all, some don't) just like your plant.

Euphorbias come from all over the world, though most succulent ones grow in Africa. Cacti are only from the Americas. Euphorbias bleed white, very few cacti do, and the ones that do don't bleed as heavily as a Euphorbia. Cacti can have paired spines but usually it is one or many. Euphorbias never have areoles where spines or hairs radiate out from a single point like a cactus. Cacti have showy flowers while Euphorbia's generally do not (I'm tempted to say virtually never but that would require a deeper botanical discussion than you may want).

The more cacti and Euphorbias you see the easier it will be to tell the difference when presented with a plant you've never seen before.

Do you happen to know what kind of Euphorbia it might be?

Someone else thought it might be virosa but I didn't think so because it doesn't have brown vertical lines along the column of spines. Could this be because it is a young plant our a different variety?

[greenknight]

It's young, and etiolated (had weak growth due to inadequate light, which is why it sunburned so easily). Once it makes some new, stronger growth you'll be able to identify it with more confidence. E. virosa was the best candidate I could come up with, but I'm far from certain.