About the genus
Blossfeldia was first discovered in Jujuy Province, Argentina and described in 1937 by Erich Werdermann. It was thought at the time to be very rare but has since been found over large areas of Argentina and southern Bolivia, having been overlooked due to its small size and tendency to inhabit narrow crevices in rock faces.
There are differences between individual plants in size, clustering habit and flower structure but to claim that these represent a wide range of separate species is absurd, and you cannot go far wrong calling them all Blossfeldia liliputana and using cultivar names if you want to differentiate between particular plants.
With age, most specimens tend to cluster. Adult plants flower on and off from April onwards for up to six months, and once a Blossfeldia starts flowering you will never be short of a supply of seeds as these are produced in great numbers by all flowers whether they open fully or not.
How to grow them
Known as being the smallest of all cacti, Blossfeldia appears to have the fewest stomata per unit area of surface of any photosynthetic plant and be capable of a very large degree of dehydration without coming to any harm. Most of the cultivation advice you find for adult Blossfeldia seems to suggest you should treat them like seedlings with regular spraying and shading against strong light. This is unnecessary and, once past the seedling stage, they thrive on a hardy regime
Grow them in an open substrate, give well-spaced waterings with the mix allowed to dry out in between, and plenty of light and a long, cool, completely dry, winter rest. They can take the full sun on a south-facing wall in a conservatory where shade temperatures can easily reach the high 30s on summer days though in a greenhouse they would need a little shade. The dry winter rest causes shrinkage but does them no harm and they soon fill out when watering starts again. Even after many decades of growth and clustering, no Blossfeldia will ever need more than a 10cm pot.
Given the size of their seeds, blossfeldias are not the easiest of plants to raise from seed but neither are they impossible, just tricky. Sow the seeds on the surface of well-drained damp seed compost in 5cm pots and seal in plastic bags with a small splash of water added to the bag before sealing. Leave well alone for a year, just giving plenty of light (but no direct sun) and only open the bag to add another splash of water if the contents of the bag appear to be dry. After a year, open the bag but leave the pot in it and add water to the bag when the soil appears to be drying out, and do this for another year. After this the bag can be discarded and the plants potted up. Although they are very tiny at this stage, fight the temptation to treat them like seedlings of other cacti of a similar size. They are much tougher than they look and can take the same treatment as other two-year-old cacti.
Text (adapted) and photos by Bob Humphrey.
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