I've read the same but I don't believe it. Not in different pots anyway. Pretty sure that's right up there with the tooth fairy and the yeti. Mine grew in pots right next to each other...and grew like weeds.
A quote from "The Portuguese Sundew (Drosophyllum lusitanicum Link.) in nature and cultivation" (Jan Flísek & Kamil Pásek):
http://www.bestcarnivorousplants.com/Drosophyllum_lusitanicum.htm
"Another widely perpetuated myth is that Drosophyllum plants do not grow close to each other in its native habitat due to the production of inhibitors which suppress the growth of surrounding plants (Pietropaolo et al., 1986; D’Amato, 1998). According to our observations in nature and cultivation and also investigations by Miguel Porto (personal communication, 2000), the plants can grow side by side (several centimeters distance) without any negative influence on their growth. The fact that at some localities Drosophyllum is dispersed over large distances is likely the result of very harsh conditions and high mortality of the small seedlings rather than inhibitor production."
I top watered them only to keep the soil moist, never soaked. I read damping off was a huge problem with seedling Drosophyllum so I was cautious not to let them go dry or get saturated. I didn't lose any of the seedlings I had to damping-off.
The number of medium sized plants I lost due to mom-not-watering-while-I-was-in-Colorado on the other hand......
I also encountered a good bit of information, including from BCP.com, that suggested that Drosophyllum seems perfectly happy growing amongst its siblings in the same pot. It is only my personal opinion, but I believe that environmental factors may play a more decisive role in spacing the plants out in nature.
While I do not disagree about the importance of calcium availability to most plants, it should be noted that people who are very experienced growers have stated the reason for Drosophyllum's intolerance to root disturbance has to do with it's inability to form adventitious roots, which is why root, leaf, and stem cuttings do not work exvitro, ever. I am unaware of it working invitro.
Also, the term "complete fertilizer" applies to any fertilizer that has the three main macro-nutrients (N-P-K). Most commercially available "complete" fertilizers do not contain calcium unless explicitly stated in the ingredients. Calcium is considered a "micro-nutrient" and is usually available in organic fertilizers like kelp meal & bone meal, and also available in soil amendments like lime & gypsum. Bone meal is used extensively to boost calcium availability in soil for garden plants that produce edible fruit, but calcium is mostly ignored for growing plants that are not explicitly grown for fruit ("leafy greens").
That being said, I think you might be getting calcium confused with phosphorus, which aids in root development and flower production (phosphorus promotes flowering, calcium grows the fruit after words). Many people who grow cactus plants do add bone meal to their soil, citing increased growth rate due to the calcium made available to them. Drosophyllum, however, is no cactus. But if you are going to experiment with calcium and its affects on Drosophyllum, I would start by adding bone meal to the media the same way cactus growers do, and skip the "complete fertilizer" route entirely. Bone meal doesn't just provide calcium, it also breaks down into soluble phosphorus that is usable by plants. Another possibility is gypsum, which contains both calcium and sulfur. It has a slight acidifying effect on the soil, and the sulfur seems to be harmless to CPs. A liquid seaweed extract added to the soil at biweekly or monthly intervals would most definitely increase macro- and micro-nutrient content in the soil gradually and might be worth trying on a separate control group but I have no idea what concentration to recommend, and I think it would be a roll of the dice.
That's just my 2c, feel free to ignore everything I just said.
I appreciate your feedback and your anecdotes about your experiences. As I said, I have no experience with Drosophyllum, but I do have significant experience with hundreds of other species, some of which include Amborella and Welwitschia. I am often asked either to grow plants that have never been cultivated, or to grow plants which are known for having significant hurdles in cultivation. Your comments about the lack of adventitious root production could very well imply an issue with hormones in Drosophyllum. Now, my next question, as an inquisitive horticulturist, is why. Is this a genetic trait? Is it related to hormones at all? Could it be related to a lack of nutrition either in developing hormones or in having enough nutrition to
form roots correctly? Is the plant strongly taprooted (lots of taprooted species, especially xerophytes, forsake adventitious roots in favor of reaching the water table)? Could we apply hormones like auxins and cause a Drosophyllum to become less susceptible to transplant shock?
I can only bring what information I've collected as well as personal experience to bear on this, but I believe there are many unknowns with Drosophyllum. As far as I have ascertained, there is also no public facility in Georgia growing this plant so I also lack any region-specific information. I was at the ABG two weeks ago and did not see one, but perhaps they've got some in their off-limits greenhouses.
My experiences with precisely adjusting the nutrition of the plants I grow have been overwhelmingly positive. I grow ~$5 mil worth of corn for a researcher and when I began supplementing additional calcium he said his seed set and microscopic cellular images were the best he'd ever been able to get in 20 years of continually growing corn. I am still unsure of what it did to improve the cellular structure. I have been given plants that others have been unable to flower for months, and within a couple weeks I had set flower buds on them using calcium. For certain crosses that would not set seed, adding some calcium to their food caused them to go from 0% yield to 60% and upwards. My sunflower people were having trouble with their seeds forming radicles in their petri dishes, and a squirt of calcium fertilizer in a petri dish stimulated radicle elongation the same day. I am not saying it's a magic solution, but I have seen that to be lacking can cause severe problems. I have also seen plants lose immune system function because of malnutrition and become susceptible to pests and diseases. A couple years back, I noticed that calcium was not listed in most blends of liquid feed as well as Osmocote, presumably because the best way to do that (CaNO3) is extremely hydrophilic and turns the blend into slush by sucking water straight out of the air.
Again, it's not a magic bullet, but probably since many horticulturists don't notice it isn't included in most fertilizer blends, it is one of the most common deficiencies in container horticulture. However, my tried-and-true first step when approaching a new plant of any kind is to eliminate nutrition as a variable. I do this by providing all 16 macro and micronutrients using a custom, dilute blend of J. R. Peters fertilizers. When I took over growing our CP collection I began putting it on the Nepenthes; they made the biggest pitchers anyone had seen on the plants in 15 years, and they flower and pitcher constantly. To test when something needs calcium, I prefer calcium nitrate as this is a purer way than gypsom, bonemeal or limestone. I may not have used the term "complete" as it is typically known, but what I meant is that I want to be sure Drosophyllum can access small quantities of all nutrients. That way, if I kill it, I can be assured it's got to be a disease or something else. Granted, I may be biased and my opinion on how to try and grow Drosophyllum only amounts to an educated guess. However, from the photos I have seen (books, forum threads, etc.) of plants where the owner noted that it later perished, I noted the following which are indicative of a calcium deficiency:
-burned leaf tips
-problems with meristematic tissues (flower buds, fruiting, death at flowering)
I rarely saw problems indicating phosphorus (the leaves turn red due to a buildup of anthocyanins) and it seems much more likely that Drosophyllum can get this nutrient from prey. Bugs contain very little calcium but a good bit of phosphorus (
http://www.organicvaluerecovery.com/studies/studies_nutrient_content_of_insects.htm).
My biggest question, germination aside, is why this is such a short-lived plant in cultivation. What's everyone's longest-lived specimen? I read many accounts of death after 2-3 years. Maybe it's a short-lived perennial, or monocarpic like Agaves. I also read that its lifespan isn't known yet because it hasn't been in cultivation long enough. I know its susceptibility to root rot, but sometimes this thing appears to just die for no reason at all, and plants just simply don't do that of their own volition.
I just really want to get to the bottom of this and play around with some living, breathing Drosophyllum, perhaps torture them a bit, and explore why they don't like to stay alive.