Bulgaria Post issued the cactuses stamp series in one set of 4 stamps and one souvenir sheet composed of one stamp. The species of cactuses. were depicted are Artichoke cactus , Mammillaria, Octopus cactus, Astrophytum asterias.
Artichoke cactus (Obregonia denegrii)
The artichoke cactus is found in semi-desert and shrubland at elevations of around 600 - 700 metres above sea level. It is often found on rocky, gentle slopes in limestone gravel.
0.10 Leva - Octopus cactus (Rathbunia alamosensis)
Octopus cactus is a species of cactus native to Mexico.It is viviparous (that is, the seeds germinate before leaving the parent plant), apparently an adaptation to living in coastal plains which are prone to flooding.
0.50 Leva - Mammillaria (Mammillaria pseudoperbella)
Mammillarias have extremely variable spination from species to species, and attractive flowers, making them specifically attractive for cactus hobbyists. Most mammillarias plants are considered easy to cultivate, though some species are among the hardest cacti to grow.The genus Mammillaria is one of the largest in the cactus family (Cactaceae), with currently 171 known species and varieties recognized.
0.60 Leva - Artichoke cactus (Obregonia denegrii)
This small cactus is just visible above the surface of the ground, as the heads emerge only slightly from the larger underground root system. The distinctive appearance of the head, which has given rise to the common name of 'artichoke cactus', is formed by the spirally arranged, erect tubercles; at the tip of each, there are 3 - 4 flexible spines. White flowers emerge from the centre of the whorl of tubercles, and these develop into whitish-brown fruits if cross-pollination is successful.
1.50 Leva - Star Cactus (Astrophytum asterias)
Astrophytum asterias is a species of cactus that is native to the lower Rio Grande Valley of Texas in the United States and the states of Nuevo León and Tamaulipas in Mexico.
Astrophytum asterias is spineless and squat, reaching a height of 2.5–6 cm and a diameter of 5–15 cm . In the wild, they flower throughout most of the summer season.Its decline in the wild has been largely attributed to over-collection and poaching. Astrophytum asterias is listed as endangered by the United States Fish and Wildlife Service vulnerable by the IUCN and critically imperilled by The Nature Conservancy.