ok, a quick primer on rhizomatous gesneriads......
The first one I grew was a mini that I started from seed.... and after it flowered, it died back. As I was a newbie and didn't realize it was rhizomatous in a bulb-kinduva way, I threw out the pot. *poof*
So the first lesson, guys and gals, is to know that the plant has a rhizome. Or, if you're like I was when I first started with these things, write it on the back of the tag. That way, when you see the empty pot, you can check the tag before you toss it.
Now, can you name five rhizomatous gesneriads?
Here are some:
Achimenes
Kohleria
Phinaea
Smithiantha
Eucodonia
Diastema
Gloxinia (the real one, not the Florist's Gloxinia which is really a hybridized Sinningia speciosa, a tuberous species)
I think there are others but I'm not coming up with them right now. Let's see here. Achimenes has been used as a bedding plant in some parts of the world. Kohlerias are becoming very popular these days and quite a bit of hybridizing is going on to create more compact floriferous cultivars. Phinaea is a mini of botanical interest. Smithiantha is gaining popularity among hybridizers too. Eucodonia - not sure about this one, but it is sold by a few plant (non-gessie) nurseries too. Diastema is another mostly of botanical interest. Gloxinia is grown somewhat but it's another genus I don't know all that much about, other than that many of the Gloxinias were moved to another genus, Seemania, in a publication in the spring of 2006.
What's the difference between a rhizome and a tuber?
A tuber is an enlarged storage area on the root, whereas a rhizome is a thickened section of plant stem. Both tubers and rhizomes can be at the soil surface or below, although rhizomes in gesneriads are usually just below the surface.
So what does one of these rhizomes look like?
Many are scaly things that look like grubs. (I freaked the first time I found one in the pot.) Each scale is viable and will produce a plant, although it's more common to break the rhizome into 1-2" pieces and plant them like that. Others look more like eggs, and no doubt there are other shapes I have never seen.
Do they all go dormant?
No, not all will go dormant, and it also depends on the growing conditions. For example, if you grow at a steady warm temperature under lights, some of them will not go dormant. Others will always go dormat between flowerings regardless of temps or day length. Stressful conditions in either direction (e.g., hot or cold) can induce dormancy.
How do I store the rhizomes?
While dormant, many of them must be stored moist or they will dry up completely. Others, like Achimenes, are said to rot unless kept dry. Eucodonia might be another to keep dry.
How do I know when to pot them up?
If you store them out of the pot, you can store them in a plastic bag with perlite. Many people hang the bags off the side of their growing shelves. When they start to show growth, pot it up.
How do I propagate a rhizomatous gesneriad?
Well, scaly rhizomes can be broken up into little pieces. You can also root cuttings and they will form rhizomes. The species can be propagated by seed, but obviously, if you propagate a hybrid by seed, you will get a generation of hybrids that are not exactly the same as the parent. Many seem to produce more rhizomes when they are pot bound.
Corrections, clarifications, additions are welcome :-)
The pic here is a sprouted smithiantha on the left, and a Phinaea on the right.
