I have to say that for the most part of my cactus collector life, I never really noticed the variations in color. But recently I could not help become completely taken with “the blues”. From what I can tell, most deep blue cacti are of the columnar variety, pilosocereus, cipocereus and of course azureocereus imperator (or browningia hertigliana, don’t know the difference). So here are some photos of the blues I own.
This is my azureocereus, and yes, I know, it is not blue yet, but I haven’t lost hope. These are not easy to purchase online in the US and I got this, along with most of the other blue cacti in this post from Giromagi in Italy. This is a photo of what an adult one typically looks like.
Azureocereus imperator
I also got a few cipocereus bradei in the same order. They were relatively small but have picked up considerably since. They had some black spots and other fungus-like type of scaring by the time they got to me but nothing some serious fungicide didn’t fix.
Cipocereus bradei 
Pilosocereus odilensis
Some pilosocereus cacti are famously blue. I have several p. azureus, from giromagi and from arid lands nursery. They have grown a few inches in one summer, which is much more than any of my other columnar cacti. While p. azureus are for sure good-looking cacti, I really hope to get my hands on a p. glaucens one day, like the ones roaming the gardens of Venice Beach in these photos.
This is another blue cactus I don’t own: I took this photo a couple of summers ago at the Cactus Store NYC, a pop-up store echoing the LA-based Echo Park Cactus Store. I do not know what it is but I would sure like to find out.
Another famously blue cactus, this time not a columnar, is melocactus azureus, the tropical cephalium-producing cactus. I have several of these and I have also started growing them from seeds. They are the fastest growing of the melocactus seedlings I sowed – the ones below are 8 months old. The two adult plants are from Arid Lands, the bright green one in the center, and from CalCactus. Disclaimer: This one used to be bluer but lost some of its color due to the neem oil I have been spraying to prevent spider mites infestations.
