How we grow our Mexican Pinguicula

Detailed description

Preface:

Many growers of this group of plants warn not to grow them as we do here at Tropical-Mesa. Some also claim that these Mexican species and their hybrids that have a heterophyllous growth habit (different leaf shape that varies with the season), are dormant when in winter leaf form. We do not entirely agree with this interpretation. Many of these species also flower when they are in their winter leaf form, some only flower from their underground, winter rosette. Our understanding is that "dormant" plants neither grow nor flower.

However, if you don't feel comfortable growing them as we describe here, don't feel obligated to do it. Descriptions of more typical cultural guidance can be found at many other sites: pinguicula.org, CPUK Forum, or TerraForums as well as many contemporary books published on Carnivorous Plant culture.

Details of our technique:

Light is the only environmental factor we would consider more important than any other, but they all contribute to the balance; and the balance is the truly important issue. The optimum amount of any factor, light included, must be balanced by all the others. Learning to juggle, is a "must" for anyone serious about growing CP, well. My cultivation techniques, described here, focus on providing optimum levels of the most environmental factors possible, in order to encourage the plants to grow and look their best.

It has been officially determined that most all Pinguicula are subject to a crown rot disease which can quickly destroy, even plants that appear healthy. This disease is said to be precipitated/vectored by nematodes, whose attacks are well known to cause problems throughout both the plant and animal kingdoms. Our growing technique incorporates several environmental factors known to affect nematode behavior, including reproduction.

1) Nematodes are known to be repelled by strong light, especially with light in the UV spectrum. So we use fluorescent lighting with its inherent high lumen to heat ratio and high amounts of UV spectrum light - this also provides the plants with a nearly unlimited (limited only to the number of lights that will fit in the space above the plants) amount of photosynthetically active radiation (PAR), this is light usable by the plants for growth and these lights also include a significant amount of UV spectrum light to possibly repel nematodes.

2) Nematode cuticula (skin) and eggshells are believed to be composed largely of chitin, as are the exoskeletons of insects and many other invertebrates. So we began using "freeze-dried bloodworms", as sold for feeding tropical fish. We ground it to a powder and lightly dusted the leaves of our plants periodically. At first, we used this just to provide nutrition that we believed was lacking due to a scarcity of natural prey in our indoor growing area. We later realized that this practice might also be providing an increased measure of protection from nematode attack, for several possible reasons - see below. Eventually, due to the cost of "freeze-dried bloodworms", we obtained a "bug-zapper" and now collect our own insects, which we dry and then powder, adding a little Trichoderma harzianum inoculum and a small amount of iron oxide powder to the mix. We incorporate all this into our growing regimen in order to inhibit the proliferation of nematodes and hopefully the trouble they can cause.

More specific details:

Always keep them wet:  We use the tray method of watering, but keep an eye on them, if the tray runs out of free water, we add additional water, but before the media in the pots becomes dry. We use shoebox sized plastic trays, available from most stores carrying household supplies. We spray-paint them with white paint, formulated for plastic, and with a satin -vs- gloss finish. This helps delay the degradation the trays experience being close to the fluorescent lights (UV exposure).

Light:  Mexican Pinguicula originate near the equator, even though they usually choose a niche where light intensities are less than maximum, it is still quite a bit higher in intensity than the same exposure would be in a latitude farther from the equator. And, too, their day length changes very little throughout the year. We use the least expensive 4 foot long fluorescent shop-light fixtures, less than $10.00 each from major building supply retailers, and the cheapest cool-white fluorescent lamps. We only replace lamps once they no longer light. We use a photoperiod of between 12-14 hours per day, running them at night in order to reduce cooling costs. [High light intensity, especially UV is said to inhibit nematodes.]

Temperature:  Lows of 50-60F and highs of 85-90F work well for us. We are located in the U.S.A. desert southwest, so our outside temperatures are quite high during our late spring - summer - through early fall seasons and during the winter we can get lows of about 20F for short periods. So we keep our Mexican Pinguicula indoors to better maintain optimum temperature, light, and humidity levels.

Water:  Mineral-free water is not as crucial with Mexican Pinguicula as it is with many other carnivorous plants, but when using the tray method it can still be an important way to keep minerals from eventually building up to toxic levels in their media.

Humidity:  Not too critical - as long as there is a good supply of water in the trays. More critical if the trays have gone dry and the only free water available to the plants is in their media or their own tissues.

Media:  We have successfully grown these plants in many different media, and combinations of media ingredients. Presently we have discovered that most of them do very well in a nearly all-mineral media. Using an all-mineral media base was inspired by Eric Partrat of Pinguicula.org. My media of choice is a mixture of Schultz Aquatic Plant Soil (APS), silica sand, and iron oxide powder. we use approximately equal amounts of APS and silica sand, but after we pre-moisten these two separate ingredients, we sprinkle a little iron oxide on the sand and mix it in until the sand is a uniform color, then we mix the APS and iron oxide coated sand together before use.

 Certain species, and hybrids derived from them perform better when their media includes some calcium containing minerals. We prefer to use sand-sized Aragonite particles, a mineral composed primarily of crystalline calcium carbonate -- this is sold as substrate for salt-water aquaria. One of these calcium-loving species is Pinguicula gypsicola, and another is Pinguicula gracilis.

Pots:  We use plastic pots of several sizes, which are usually available in a shade of green, but when we can get them, we use plastic pots that are white. We find that most of these Mexican Pinguicula plants have very meager root systems, despite using all-mineral media, and that most will grow, unhindered, to their full, adult size in even the smallest pots. So, the size pot we use most is 2 inch square (5 cm) - this permits 18 pots to fit - three wide, into the shoebox sized plastic trays we use most. We usually only use 15, 2 inch pots per tray to make watering and moving pots around, easier.

Nutrients:  We began incorporating iron oxide powder into our media to combat chlorosis which we were experiencing with some of our plants. We also heard of others using food prepared and formulated for tropical fish, and decided to try a product called, "freeze-dried bloodworms". We first grind these into a powder and lightly sprinkled them on the surface of the plants leaves and then lightly spritz with purified water to facilitate their interaction with the plants' digestive mechanism. This seemed to have a positive and dramatic affect. [We particularly like the use of dead, dried, powdered insects due to their chitin content, since nematode cuticula (skin) and egg-shells are both composed of chitin, the hypothesis being that decomposing chitin in the root-zone increases the populations of chitin-digesting micro-flora, thereby inhibiting nematodes.] It has just come to our attention that Trichoderma harzianum is just such a chitin-digesting microorganism, it attacks and breaks down chitin, using several different mechanisms, so incorporating some of this inoculum into our powdered insect dust fertilizer seems even more appropriate than we had, at first, thought.