Yearling plant of E. paradoxum, grown from seed, producing
its first enations.  The leaf is about 3 mm long.

     In general, cultivating eriospermums is similar to cultivating other winter-growing succulent plants from South Africa, like conophytums or tylecodons.  A sunny, cool greenhouse with plenty of air circulation is just about essential, though one could probably keep them going on a windowsill that gets five or six hours of direct sun each day.  In places like southern California, with climates similar to the Eriospermum motherland, they do very well outside with only enough cover to keep off excessive rain.  Below is a summary of the horticultural practices for erios that I use here in Connecticut (northeastern USA).  For a somewhat more in-depth discussion of the cultivation of winter-growing succulents, see my  Conophytum Page.  Most of my advice for growing Conophytum plants is applicable to eriospermums.

The Annual Cycle.  Or: That is not dead which can eternal lie

     One of the really critical points to keep in mind when cultivating erios and other winter-growing succulents is that you must respect their growing cycle.  Eriospermum tubers are dormant during the summer, at which point their pots can be stored somewhere out of direct sun, and given only light waterings when the soil is bone dry.  In early autumn (September in my hemisphere) they should be given deeper waterings to encourage them to wake up.  Happy, mature plants will flower, and then send up their leaves.  While they're growing, you should water your eriospermums whenever the soil dries.  Try not to let them dry out to the point where the leaves wilt.  Some sluggish plants may not produce any growth for months, or may elect to stay dormant for the whole season -- just keep watering these goldbrickers as you would an active plant, and hope for more action next year.  No, growing eriospermums is not an appropriate pastime for those who fidget while waiting two minutes for their microwave burritos.
     The leaves will remain green all winter and into the early spring, photosynthesizing and sending sugars down to the tuber.  In mid to late spring (April or May for me), the leaves yellow and wither, and the plants are ready for another dry summer rest.
      Sometimes people in the northern hemisphere wonder if they have to keep track of what season it is in the southern hemisphere when they grow plants from South Africa.  The answer is no: the plants take their cues from the daylength and temperatures of whichever hemisphere they're growing in, and adjust their schedules accordingly.

Soil and Nutrients.

     Whatever well-drained mix you normally use for succulents is probably good enough for your eriospermums.  I mostly use a "native soil" mix based upon sandy-loam soil with added perlite and Turface MVP (calcined clay chips) for aeration.  Soiless mix (e.g. Promix)-based media also seem to work well enough.  I've had fairly crummy results with coir-based soils, though some excellent growers out in California swear by the stuff.
      Eriospermums seem to have modest needs for mineral nutrients; a few doses of balanced, water-soluble fertilizer at half-stength over the course of the growing season are sufficient.  I've never noticed any special need for trace-mineral supplementation, either.

Pests.

     In my experience, erios have few problems with pests; even the dread root mealybug seems to leave them alone.  I have seen occasional damage from thrips, in the form of small yellowed spots on the leaves, but it hasn't really been bad enough for me to break out the pesticides.

Propagation.

      Vegetative propagation is possible for the species that produce offset tubers, or multiple growing points.  Daughter tubers can be broken off of the original tuber when they have had a chance to grow for a few seasons, and have reached a decent size (1/4 to 1/2 the size of mature tubers is probably safe).  I have had good success dividing Eriospermum tubers at the start of the growing season, and keeping the soil barely moist for a week afterwards, to allow the cut surfaces of the tuber time to heal.
      Raising eriospermums from seed is also an amusing project.  To produce your own seed, you will probably need to have two individuals of the same species flowering at the same time -- transfer the pollen between plants with a brush or your finger.  Some eriospermums are marginally self-compatible, and will produce a few seeds from pollination of the flowers of a single individual.  Fresh seed germinates rapidly and completely if sown just beneath the soil surface and kept moist; seed shouldn't be more than a year or two old for good results.  The seedlings should be kept consistently moist for their first season, given dilute fertilizer every few weeks, and be exposed to as much light and fresh air as adult plants need.  Under my growing conditions, they take about three years to reach flowering size.  Species-specific elaborations of the leaves, like enations in E. paradoxum (see photo above) or the bladder cells of E. titanopsoides, are not present in the earliest true leaves, and can take several years to manifest themselves.