Q: Roridula cultivation
R. gorgonias
R. gorgonias
R. dentata
A: I follow Matt Opel's method of growing Roridula and have had, so far,
good luck. However, I have an advantage because I happen to live in a more-or-less Mediterranean climate
(in the central valley of California), so my conditions are predisposed to growing Roridula.
The key to growing Mediterranean-climate plants is to give them a long, hot, relatively dry summer and a cooler, moist winter.
Those are the conditions that Roridula expects in South Africa. If you do not have conditions like
that, I can only wish you good luck but have little advice for you!
I have almost only ever seen Roridula sold as seed. So your first job will be to get good germination. I have
tried to germinate Roridula gorgonias seeds only about four times. Each time I was
unsuccessful, except for once. On my one successful attempt, I had great results with fairly high germination rates. I did
nothing different. Go figure. All my germination attempts were on a pumice:sand:peat (1:1:1) mix. Coercing
germination from Roridula dentata is reportedly more difficult. Experts recommend that you do one or
both of the seed treatments called scarification and smoke water.
I have found no difference between using smoke discs alone, vs. smoke discs combined with scarification. However, my experiments
were small scale, so I cannot make confident pronouncements.
To scarify the seeds, scratch them very, very lightly with
sandpaper. The seeds (which look exactly like mouse poop) are surprisingly soft (just like mouse poop), so be careful. (The first time I scarified Roridula,
I smeared the entire seed into mush with a single long sweep on sandpaper!)
For smoke water stimulation, use either a pot-fire, smoke disc, or something similar. Interestingly, when moistened the seeds
of Roridula dentata exude a coating of mucus. I do not recall if
Roridula gorgonias does the same.
Germination could take up to six months. Once you get germination, you should be careful about excessive moisture---too much
humidity, or pots that are more than barely moist, can harbor fungi that will kill your plants. I estimate I have lost
80% of my plants to fungus within their first two years of growth.
Once the plants survive past their first year, they are pretty sturdy. They require full sun for most of the day, moderate humidity,
and barely moist soil. I germinate seedlings in large pots, so have never repotted them. I just grow them in a
2:1 peat:perlite mix. Temperatures are best below 38°C (100°F), and my plants survive the occasional light frost.
A foliar spray of 1/4 strength acid-fertilizer has not killed my plants, but
I am not sure it has helped them, either.
Propagation is reliable only by seed, although Opel reports marginal success with stem and root cuttings and one internet
grower reports success with stem cuttings for Roridula dentata. Seeds are produced
by selfing plants, although more vigorous progeny result from crossing plants.
Page citations: Hartmeyer, S. 1998; Opel, M. 2005; Rice, B.A 2006a.
