Family Cactaceae > Subfamily Cactoideae > Tribe Trichocereeae.
There are 120 to 180 species depending on the inclusion or not of the old genera
    of Lobivia and Trichocereus.
Hedgehog or Sea urchin cacti are from South America.
The species are very variable in appearance and there are hundreds of hybrids.

They can be small globose cacti up to large, branching, tree-like ones.
(Lobovia species were smaller plants while the Trichocereus were taller ones.)
They all have slight to prominent ribs.
The areoles have woolly hairs and straight or curved spines.

Flowers are large in relation to the size of the plant.
There are some coloured day opening species but most are white night opening ones.
Coloured ones are yellow, orange, red or pink commonly with blends of two or more colours.
Flowers only last 1 day but new ones appear over a long period.

The funnel-shaped flowers are up to 15 cm across.
The long tube or hypanthium has hairs or scales.